Polytek catalog - Sculpture Workshop

MOLD MAKING & CASTING 

Manual & Catalog 

Discover the 

Flexibility of 

Liquid Mold 

Rubbers and 

Casting 

Plastics 

10th Edition 

Advancing the State-of-the-Art in Art & Industry TM

WELCOME! 

Welcome to the 10th Edition of Polytek ® Development Corp.’s 

MOLD MAKING & CASTING MANUAL & CATALOG. We wrote this 

manual to help you use the many products and materials Polytek 

offers to their maximum benefit. 

Mold making and casting are not easy. In fact, making molds and 

castings is a full-time career for many skilled craftsmen. 

An important part of a master mold maker's expertise is developing 

a “feel” for the way each different molding and casting material 

behaves. Developing this “feel” for each material and learning 

to anticipate and avoid common problems takes a great deal 

of practice with a variety of materials. Consequently, it is difficult 

for anyone to try a new technique or use a new material the first 

time and achieve perfect results. Thus, the old adage, "Practice 

makes perfect." 

Polytek has formulated a range of materials to help you achieve 

your molding and casting objectives, and we are constantly working 

to invent new products to make your job easier. 

As good as any material may be, however, the skill of the user is 

equally important in achieving the objective. When you use a 

material for the first time, we ask that you start small and simple 

to get a “feel” for the material before going on to larger projects. 

Our goal is to continue to produce dependable, 

quality materials and present their 

basic methods of use. The rest is up to you. 

We depend on your success and want to 

help whenever possible. 

Thank you for your patronage. 

Sincerely, 

Bob LeCompte 

Chairman 

POLYTEK’S LOCATION 

CUSTOMER SERVICE 

When you call Polytek, you can speak to a member of our customer 

service team (Joe, Stan, Wendy, Dave, Laurie, Jill, Mary, Larry and 

Bill). They all have hands-on experience and the knowledge and ability 

to satisfy your needs quickly. Whether you’re new to mold making 

and need help getting started or an expert mold maker looking for 

a fresh perspective, we welcome your questions. We know that our 

continued success is based on the quality of our products and service 

and the word of mouth of satisfied customers. 

MOLD RUBBERS & CASTING PLASTICS 

Polytek offers the most complete line of mold making and casting 

materials available anywhere. For mold making, Polytek produces 

polyurethane and silicone liquid rubbers in many hardnesses 

as well as latex, alginate and wax. For casting, Polytek 

manufactures rigid and flexible polyurethane plastics and foams 

and castable epoxies. Polytek is a one-stop source for mold making 

needs: we offer a full line of accessories including release 

agents, training DVDs, scales and more. If we don’t have what you 

need, call us -- we can develop custom formulas within weeks. 

SEMINAR & WORKSHOP 

Our state-of-the-art facility is located at 55 Hilton Street, Easton, 

PA -- just off I-78, Exit 75. You can see us from the highway! 

Stop in! We use our 5,000-ft 2 mezzanine for product demonstrations, 

trials, and seminars. Take time to enjoy nearby historic 

Delaware River inns and attractions. We’re only 90 minutes to 

New York City and Philadelphia. 

Polytek offers a popular, two-day seminar and workshop titled 

“Mold Making and Casting Methods and Materials.” The first 

day begins with a comprehensive presentation and demonstration 

of mold making techniques and materials. Later in the day the 

workshop portion gets started. Attendees are encouraged to bring 

a small, simple model. Polytek’s expert technicians review each 

model and discuss mold making options with the group. Then 

each attendee gets hands-on experience using Polytek’s products 

to make a mold and casting of their model. Enrollment is limited 

to 20, meaning that each attendee gets plenty of one-on-one guidance 

from Polytek’s staff. The seminars are conducted in 

Polytek’s well-equipped, 5,000-ft 2 mold making and casting shop 

in Easton, PA. The cost is $400 for the seminar and workshop 

(includes materials) or $200 for the first day only (with no handson 

use of materials). Call for seminar dates. Enroll early! 

Seminars fill fast! 

(610)559-8620 • (800)858-5990

CREATIVITY WITH CHEMISTRY 

The remarkable, life-size Carrara 

marble sculpture by E. Zocchi of a 

young, enthusiastic Michelangelo 

carving a gargoyle depicts four of 

our favorite things ... art ... 

creativity ... enthusiasm ... and 

gargoyles! 

Use Polytek products creatively 

and enthusiastically for a variety 

of projects -- from creating fine art 

to producing functional pieces for 

home and industry. Mold making 

and casting are truly CREATIVITY 

WITH CHEMISTRY. The use of 

Polytek materials is limited only 

by the imagination -- may yours 

be limitless. 

Mold Making Methods . . . . . . . . . . . . . . . . .2 

1Mold Making & Casting Materials 

Types of Flexible Molds & Castings 

Mold Making & Casting Procedures 

Applications 

Polyurethane RTV Mold Rubbers . . . . . . .32 

2Poly 74, Poly 75 & Poly 77 Series Rubbers 

Polygel ® Brushable/Sprayable Rubbers 

Poly 81-Series Rubbers 

Poly-Fast 72-40 & Poly GlassRub Rubbers 

Silicone RTV Mold Rubbers . . . . . . . . . . . .40 

3TinSil ® 70 Series Silicone Rubbers 

PlatSil ® 71 Series Silicone Rubbers 

PlatSil ® 73 Series Silicone Rubbers 

PlatSil ® Gel 10 Silicone Rubber 

Mold Making 

Methods 

Polyurethane 

Mold Rubber 

Silicone 

Mold Rubber 

CONTACT INFORMATION 

www.polytek.com 

BY PHONE 

(800) 858-5990 

(610) 559-8620 

Monday to Friday 

8:30 a.m. - 5:00 p.m. 

BY MAIL 

Polytek 

55 Hilton St. 

Easton, PA 18042 

ONLINE 

sales@polytek.com 


Secure credit card transactions 

BY FAX 

(610) 559-8626 

24 hours a day 

Casting Plastics/Resins . . . . . . . . . . . . . . .46 

4EasyFlo & Poly 15 Series Plastics 

Poly-Optic ® 14 Series Clear Casting Resins 

PolyFoam, LiteCast, Plasti-Flex & Polygels ® 

Epoxy Resins & Curatives 

Specialty Molding/Casting Materials . . . . .57 

5Latex Rubber Products 

Poly Wax 15 

Poly Skin-Wax 

Hydrogel ® N Mold Compound 

Accessories . . . . . . . . . . . . . . . . . . . . . . . . .61 

6Pol-Ease ® Releases 

PolyFiber, Bronze and Other Fillers 

Safety Equipment 

Mixers, Scales, Books, DVDs & More 

DISCLAIMER: The information in this catalog and otherwise 

provided by Polytek ® is considered accurate. However, no warranty 

is expressed or implied regarding the accuracy of the data, the 

results to be obtained by the use thereof, or that any such use will 

not infringe any patent. Before using, the user shall determine the 

suitability of the product for the intended use and user assumes all 

risk and liability whatsoever in connection therewith. 

© 2007 by Polytek Development Corp. All rights reserved. This 

manual may not be copied, in whole or in part, without written 

consent of Polytek Development Corp. 

Casting Plastics 

Speciality 

Materials 

Accessories 

1

1 Mold Making Methods 

Mold Making 

Methods 

GETTING STARTED 

When making a flexible mold of an object in order to cast 

reproductions, you are faced with many choices of mold making 

and casting materials and methods -- it can be bewildering at 

first glance. In order to succeed, you must consider many factors 

before you start a project. Here are a few things to think about: 

• What is the model made of? 

• Does the shape of the model present mold making or 

demolding challenges? 

• What will the casting be made of? 

• How many castings do you envision making? 

• How much money do you plan to spend? 

• How much time do you have to complete the project? 

Think ahead. You need to plan your project from start to finish 

before you begin. Read the “Methods” sections entirely so that 

you understand all of the factors that need to be considered 

during the planning stage of your project. 

To have a successful mold making experience, 

PLEASE ... 

• Study. Read as much "how-to" literature as 

possible. Watch instructional DVDs and 

videos (see p. 63). 

• Start Small. Make a small, simple mold and 

casting before attempting an important 

piece. Get a feel for the materials without 

costly mistakes. Experiment with small Trial 

Units (see p. 65). 

• Ask Questions. It’s difficult to tell you how 

to make molds and castings over the phone, 

but we’ll try! Please call Polytek Customer 

Service with questions. 

MOLD MAKING & CASTING MATERIALS 

Polytek Development Corp. produces nearly all types of flexible 

mold materials commonly used today as well as many casting 

materials. Before beginning a mold making project, you must 

understand the advantages and disadvantages of various mold 

making and casting materials. At the same time, you must 

consider the type of mold you envision, because that too will 

play a factor in selecting appropriate mold making and casting 

materials. For information about types of flexible molds, refer to 

pp. 7-9. 

Flexible mold materials range from simple, one-part latex (the 

natural product of the rubber tree), Hydrogel ® N (alginate, a 

powder to which water is added), and Skin-Wax (which is 

melted for use), to the higher performance two-part polyurethane 

and silicone mold rubbers. Polytek’s two-part systems consist of 

two liquids that after mixing together react to form rubber. These 

systems cure at room temperature and, therefore, are are referred 

to as room temperature vulcanizing (RTV). 

Each mold making and casting compound is unique and may 

require special handling that differs from similar products. 

Spend time learning the special requirements of every new 

product and making a small test mix before using the product on 

a larger scale to avoid loss of valuable time and materials. 

Mold making and casting materials must be selected concurrently. 

This is because some casting resins work well only in 

certain mold materials (and vice versa). If you have a specific 

casting material in mind, then you select a mold material that 

works well with that casting material. Most often you can find 

mold and casting materials that work well together and satisfy 

all of of your project requirements. The illustration below helps 

to demonstrate this point. 

Casting 

Wax 

Concrete 

Mold Material 

All (except Skin-Wax) 

Polyurethane 

Selecting proper mold making 

and casting materials for the job 

at hand is the 1 st step to 

success! 

Plaster 

Epoxy 

Polyurethane 

Polyester 

Acrylic 

Metal (low-melting) 

All (usually polyurethane) 

Polyurethane or silicone 

Silicone or polyurethane 




2 

(610)559-8620 • (800)858-5990

Mold Making Methods 1 

SELECTING A MOLD MAKING MATERIAL 

To select the best mold making material for your project, consider 

several factors: model composition, shape and size; mold type; 

cost; and timing. First, familiarize yourself with the common 

types of flexible mold making materials and the advantages and 

disadvantages of each. After you have learned about the various 

mold materials, take into account the characteristics of your model 

and the mold making challenges it presents. 

The tables below highlight advantages, disadvantages, uses and 

methods of application for various one- and two-part mold 

materials. 

One-part mold materials usually 

present more disadvantages than 

two-part materials. 

Polytek’s two-part materials are 

tough, long-lasting, easy-to-use 

mold rubbers. 

Mold Making 

Methods 

One-Part Mold Compounds 

Type Advantages Disadvantages Uses Methods 

Alginate 

Hydrogel ® N 

• Safe for body contact • Very limited life; dries out 

• Gets model wet 

• Body molds 

• Single-use molds 

• Pour 

• Layup 

Wax 

Poly Skin-Wax 

• Safe for body contact 

• Low cost 

• Fast set 

• Reusable 

• Low strength 

• Limited use 

• Must melt prior to use 

• Body molds 

• Single-use molds 

• Brush-on 

• Dip 

Latex 

Poly Latex 60 

Poly Latex False Face 

• High strength • Not dimensionally stable 

• Takes days or weeks to 

make mold 

• Oils can soften and 

destroy molds 

• Blanket molds only with 

shell required 

• Concrete 

• Plaster statuary 

• Limited resins 

• Brush-on 

• Spray 

• Dip 

Two-Part Mold Rubbers 

Type Advantages Disadvantages Uses Methods 

Polyurethanes 

• Moderate to low cost 

Polygel ® 

Poly 74, 75, & 77 Series • High strength 

Poly 81 Series 

Poly 72-40 Series 

• Many versatile varieties 

• Requires careful 

release agent 

• May be moisture 

sensitive 

• All materials 

except molten 

metals 

• Pour 

• Brush-on 

• Spray 

Tin Silicones 

TinSil ® 70 Series 

• No release agent 

needed 

• High strength 

• Excellent chemical 

resistance 

• Higher cost 

• Shrinks up to 1% on 

curing 

• Limited cured storage 

life 

• All materials 

(especially resins 

and lowtemperature 

melting metals) 

• Pour 

• Brush-on 

• Spray 

Platinum Silicones 

PlatSil ® 71 Series 

PlatSil ® 73 Series 

PlatSil ® Gel-10 

• No release agent 

needed 

• No shrink on cure 

• Good cured storage life 

• High strength 

• Excellent chemical 

resistance 

• Higher cost 

• Cure inhibited by some 

surfaces 

• All material • Pour 

• Brush-on 

• Spray 


3


Mold Making 

Methods 

Model Composition 

A model’s composition or surface coating may restrict you to 

certain mold making materials. Certain mold materials do not 

cure properly over some model materials (i.e., platinum-cured 

silicones do not cure on sulfur-containing clay models). 

Sometimes, if the model’s composition presents a problem, it 

can be overcome by carefully sealing the model (see p. 11). 

Thoroughly review product technical bulletins to be sure that 

there are no compatibility issues between your model and the 

mold material you’ve selected. If your model is delicate or 

valuable, it is best to try the selected mold material on a small 

hidden area before you jump into mold making. Fragile models 

can be damaged in the mold making process. The resulting 

mold, however, can be used to make a reproduction out of a 

more durable material. [Note: If the model is a human body, 

there are obvious safety issues. Consider Hydrogel Mold 

Compound or Poly Skin Wax (see pp. 59-60).] 

Model Shape and Size 

The size, shape, and even location of your model may limit you 

to certain mold making materials and types of molds (i.e., a 

model with deep undercuts does not lend itself to a simple box 

mold). If you are restricted to a certain type of mold, then your 

choices of mold materials may be limited. 

Cost 

Both the volume of material needed and the price per unit 

volume must be considered in calculating project cost. The 

quantity of mold making material needed is dictated largely by 

the type of mold you choose to make -- a large model may 

mandate a brush-on mold since any other type of mold would 

require too much material. The quantity of material needed can 

be calculated by estimating the volume of mold making material 

needed (in cubic inches) and dividing by the specific volume 

(cubic inches per pound) of the material (see box to the right). 

To determine project costs more accurately, one also needs to 

consider the time it takes to make the mold (see below). 

Time Considerations 

Timing plays an important role in the selection of a mold 

making material. With some materials a mold can be completed 

in an afternoon (i.e., accelerated silicone and polyurethane mold 

rubbers), while with others, it can take weeks (i.e., latex rubber). 

To learn more about demold times, read the technical bulletins 

for individual products. Remember, the fastest material or 

method may not be the least expensive. 

Consider how long you intend to use and keep the mold. Some 

materials are only suitable for one casting (i.e., Hydrogel), while 

others will hold up for hundreds of castings (silicones and most 

polyurethanes). Also, consider “library life:” how long you 

expect the mold to remain useful after sitting on a shelf. Most 

properly cured rubber molds are useable for many years, but 

some degrade within 2 to 4 years (i.e., Poly 72-40 and TinSil 

rubbers). For molds with long library life, use polyurethane 

rubbers (except Poly 72-40) or PlatSil silicone rubbers. 

$ 

Cost per cubic inch is your real cost -- 

price per pound can be misleading. 

When using mold making or casting materials you are usually 

filling a given space. The lower the cost per cubic inch of 

material, the lower the cost of filling the space. “Specific 

Volume,” expressed in cubic inches per pound (in 3 /lb), is the 

key to calculating the real cost of a mold making and casting 

material. 

Some rubbers and plastics that have a low price per pound 

contain dense fillers such as powdered marble or silica. These 

fillers typically reduce the price per pound, but raise the price 

per cubic inch. Simple calculations reveal the real cost of your 

material in terms of cents per cubic inch. 

Poly 74 Series Rubbers (see p. 34) are low density and 

contain no heavy fillers. They yield 27.5 in 3 /lb. Poly-Fast 72- 

40, a dense rubber, contains fillers and yields only 20 in 3 /lb -- 

nearly 1/3 less rubber volume per pound! 

For example: 

• An 80-lb trial unit of Poly 74-30 costs $336 or $4.20/lb 

($336/80 lb). Dividing $4.20/lb by 27.5 in 3 /lb yields a 

cost of $0.15 per in 3 . 

• A 49.5-lb trial unit of Poly-Fast 72-40 costs $194 or 

$3.92/lb ($194/49.5 lb). Dividing $3.92/lb by 20 in 3 /lb 

yields a cost of $0.20 per in 3 . 

Poly 74-30 = $0.15 per in 3 

Poly-Fast 72-40 = $0.20 per in 3 

At first glance it appears that Poly 74-30 is the more 

expensive product; however, to fill a given space, using Poly 

74-30 actually costs nearly 25% less than higher density 

Poly-Fast 72-40 rubber. The photo below shows the dramatic 

density difference between these rubbers. 

4 

(610)559-8620 • (800)858-5990


SELECTING A CASTING MATERIAL 

To select the best casting material for your project, you must 

consider several factors: mold composition and construction, 

required characteristics of the casting (i.e., weight, durability), 

cost, and timing. 

First, it is a good idea to familiarize yourself with the common 

casting materials and understand the general advantages and 

disadvantages of each. The most common and least expensive 

casting materials are gypsum plasters and cements, both of 

which are available in many formulas for various end uses. 

Waxes are castable, of course, but uses are limited by low 

hardness and high shrinkage. Low melting metals can be cast in 

heat resistant silicone molds. Epoxy and polyurethane systems 

are versatile and durable casting materials. Polyester resin is 

quite low in cost, especially if low cost fillers like sand, 

limestone or wood flour are added. 

The table below presents common casting materials suitable for 

use in molds made from Polytek flexible mold products. 

Mold Composition 

A mold’s composition may restrict you to certain casting 

materials. In a few cases, casting materials may rapidly degrade 

or even destroy the mold (i.e., exothermic epoxy resins will melt 

a wax mold). Carefully review product technical bulletins to be 

sure that there are no compatibility issues between your mold 

and the casting material. 

Mold Material 

Casting Material 

Skin-Wax Low-exotherm materials -- 

polyurethane and silicone 

rubbers and select resins 

Hydrogel 

Latex 

Polyurethane 

Silicone 

Materials that are not 

moisture sensitive -- wax, 

plaster, silicones and 

select resins 

Concrete, plaster and 

select resins 

Most casting materials are 

acceptable, except metals 

All casting materials are 

acceptable 

Molds made from Polytek products are non-porous and casting 

materials used in the molds should "cure" or set chemically. In 

most cases, air drying materials are not suitable since the rubber 

prevents them from drying except from the back. Water clay, 

paper-mache, and latex are often not suitable casting materials. 

The illustration above provides a general guideline regarding 

suitability of casting materials depending on mold composition. 

Mold Making 

Methods 

Casting Material Advantages Disadvantages End Uses 

Wax • Easy demold • Fragile 

• High shrinkage 

• Foundries 

• Candles 

• Resculpting 

Vinyl • One-part liquid • Requires high heat to use • Prototypes 

• Parts 

Gypsum Plaster • Fast 

• Yields good quality 

• Indoors only 

• Brittle 

• Most indoor objects 

• Moulding 

Concrete/ 

Specialty Concrete 

• Acceptable for outdoor use • Heavy 

• Rough surface 

• Slow set 

Design Cast and Forton® MG • Acceptable for outdoor use • Higher cost 

Acrylic Resin • Clear • Expensive 

• Difficult to use 

• Strong odor 

Polyester Resin • Inexpensive • Flammable 

• Strong odor 

Epoxy Resin • Moderate price • Health hazards 

• Limited mass 

Polyurethane Resin/Foam • Moderate price 

• Moisture sensitive 

• Easy to use 

• Very versatile 

• Statuary (indoor & 

outdoor) 

• Architectural 

ornaments 

• Many diverse uses 

(painting may be 

needed for outdoor 

use) 


5


Mold Making 

Methods 

Weight of the Casting 

Casting materials have different densities that affect the weight 

and feel of the final casting. For example, plaster and concrete 

are heavy, while resins are lighter. The weight of a casting can 

often be controlled by adding fillers to the casting material. 

Also, you can create a lighter, hollow casting, by using a "plug" 

to prevent casting material from filling the entire mold, or by 

laying up into or rotating a mold so casting material cures in a 

thin shell on the mold surface. These techniques are discussed 

on p. 10. 

Exterior Durability of the Casting 

Materials such as cement are fine for both indoor and outdoor 

environments, whereas most other casting materials need to be 

painted or sealed for outdoor use. Exterior castings are subject to 

elements such as UV light from the sun, rain, and freezing and 

thawing. Concrete and polyester resin castings are fine for 

interior and exterior uses. Polyurethanes, however, must be 

painted or sealed prior to being placed outdoors in order to avoid 

yellowing and chalking of the bare plastic, which occurs over 

time. Fillers, pigments and Poly UV Additive can be added to 

improve exterior performance (see p. 61 for information on Poly 

UV Additive). 

Cost 

Both the quantity of material needed and the price per cubic inch 

must be considered in calculating project cost. The 

quantity/weight of casting material needed is dictated by the 

volume of material needed (in cubic inches) divided by the 

specific volume (cubic inches per pound) of the casting material. 

Here is a general idea about the relative costs of casting 

materials. 

COST 

High Cost 

Medium Cost 

Low Cost 

Unfilled polyurethanes and epoxies 

Filled resins, speciality concretes 

(i.e., Forton ® MG) 

Concrete, plaster, wax, filled 

polyester 

Obviously, to determine true project cost one needs to consider 

the time it takes to make the casting (see below). 

“Exotherm” of Casting Material 

Exotherm is the heat of reaction produced as a resin or rubber 

cures. Polyurethane rubbers generally have very little 

measurable exotherm. Poly 74-55 in a large mass may rise 

just a few degrees above the temperature of the Parts A and B 

before mixing. Epoxies, on the other hand, are much more 

exothermic and, if poured in too large a mass for the heat to 

dissipate, may get so hot that they boil and burst into flames. 

Therefore, casting epoxies in large masses is dangerous and 

must be avoided. 

Consider exothermic heat when selecting casting resins. If the 

casting is so thin that exothermic heat is easily dissipated into 

the mold, the resin will be slow to cure, but there will be no 

thermal shrinkage caused by gelling while hot then cooling. 

Slow curing in these cases can be overcome by using warm 

molds or using a faster curing system. Massive castings tend 

to build heat in the center of thicker sections and sometimes 

thinner sections of the same casting remain cooler. If the 

temperature difference is too great, distorted parts or shrink 

marks may be evident. Often, warm molds can help overcome 

this problem as can addition of fillers or use of slower curing 

systems. High curing temperatures shorten rubber mold life, 

so proper selection of casting systems results in best economy 

and longest mold life. 

To reduce costs and cast larger masses, 

ADD FILLERS to polyurethanes & epoxies. 

Many fillers are suitable to add to liquid plastics to reduce 

costs and help dissipate exotherm, which can cause shrinkage 

and limit the size of the mass that can be cast at once. Heavy 

fillers absorb more exothermic heat, but result in a heavy 

casting. Lightweight fillers can make the casting lighter than 

wood so it will float and carve easily. Some fillers such as 

wood powder and nut shell flours may contain moisture and 

cause foaming of the plastic or other problems. Dry fillers that 

stir easily into the mixed resin are best. The cost per cubic 

inch of resin displaced is the real cost of these fillers. For 

example, some typical costs per cubic inch follow: 

Time Considerations 

Timing plays an important role in the selection of casting 

material. With some materials, a finished casting can be made in 

minutes (i.e., EasyFlo 60 Plastic); while with others, it can take 

days (i.e., concrete). The fastest material or method often is not 

the least expensive. 

TIME 

Slow 

Medium 

Fast 

Concrete 

Plaster, wax, thin resins 

Polyurethane and polyester resins 

Filler $/lb Density (g/cc) $/in 3 

Dry Sand $0.05 2.75 0.005 

Bronze Powder 5.00 8.85 1.590 

Ground Limestone 0.15 2.70 0.015 

Extendospheres CG 0.50 0.70 0.013 

Q-Cel 2116 or 3M C/15 6.00 0.10 0.022 

Adding an equal volume of low cost filler to a Poly Plastic 

can cut the cost of the casting nearly in half! For example, one 

cubic inch of resin at $0.14 plus an equal volume of filler at 

$0.015 yields approximately two cubic inches costing $0.155 

or about $0.07 per cubic inch for the mix. 

6 

(610)559-8620 • (800)858-5990


TYPES OF FLEXIBLE MOLDS 

There are two basic types of flexible rubber molds: block molds 

and blanket molds. Within these two basic types, there are 

numerous variations differing in both construction and 

complexity. 

Mold Making 

Methods 

BLOCK MOLDS 

Block molds are typically made by placing the model into a 

containment area (i.e., mold box) and pouring liquid rubber over 

the model. After curing, the rubber is removed from the model 

and the result is a single-piece, poured block mold. This is the 

simplest type of mold. Single-piece, poured block molds are best 

for models with a relatively flat base or back and no sharp 

undercuts that prevent the rubber from demolding from the 

model. This type of mold would be used for reproduction of a 

wall plaque. 

For a model with undercuts (i.e., the chin of a cherub’s face) a 

softer rubber can be used or the mold may need to be cut to 

allow for removal of the model and castings: this is referred to 

as a split block mold. In some cases, the block mold may need to 

be cut into or poured in several pieces to allow for removal of 

the model and then carefully reassembled prior to casting: this is 

referred to as a multi-piece block mold. 

Sometimes, multi-piece block molds are made in sections, by 

pouring on one surface at a time, allowing to cure, then pouring 

on the adjoining surface against the previous pour. This 

technique is necessary when the model has details on all sides 

(i.e., does not have a flat base or back). 

Poured molds are sometimes free standing if the rubber is thick 

enough to hold its shape, but often a box or rigid shell is used 

with the mold to maintain its shape. Generally, the box or shell 

(“mother mold”) must be separate from the rubber mold in order 

to allow the mold to flex for removal of the model or casting. 

Various molds and castings of ornate architectural elements 

and decor. 

Poured mold materials generally pick up detail with fewer 

entrapped air bubbles than materials that are applied by brush or 

spray, except where bubbles on the surface of the rising liquid 

are trapped under a ledge such as under the chin of a head 

model. Tilting the mold box while pouring is a useful technique 

for preventing air entrapment. If this does not help, a brush-on 

mold, or pouring one section at a time may be advised. 

For diagrams depicting the procedures to make a single-piece 

poured block mold, a split single-piece poured block mold, and 

a multi-piece poured block mold, see pp. 17-18. 

A note on the terminology: Since a block mold is often made in 

box shape, it is sometimes called a box mold. However, this type 

of mold can be made in any appropriate containment area (i.e., a 

cylinder such as a piece of PVC pipe). Also, block molds are 

sometimes referred to as poured molds since this is the method 

used to make them. 

Mold Complexity 

Complexity 

Multi-Piece Poured Blanket Mold 

Poured Blanket Mold 

Sprayed Blanket Mold 

Brushed Blanket Mold 

Multi-Piece Block Mold 

Contributing 

Factors: 

Size 

Location 

Shape 

Time 

Materials 

Single-Piece Block Mold 

Two-piece block mold 


7


Mold Making 

Methods 

BLANKET MOLDS 

As the name implies, blanket molds resemble a thin blanket 

carefully placed around the model. Blanket molds are made by 

either brushing or spraying the flexible mold material onto the 

model or pouring the mold material into a pre-constructed shell 

around the model. With a few mold materials (i.e, latex, wax), it 

is possible to make a blanket mold by dipping the model into the 

liquid material. Blanket molds are generally ¼- to ½-inch thick. 

To hold a blanket mold in its proper shape after the cured rubber 

is removed from the model and during the casting process, a 

rigid or firm mold shell (“mother mold”) is required. 

Blanket molds are often mandated by the size and/or location of 

the model. Since blanket molds consume far less rubber than a 

conventional block mold, they are preferred for large or 

irregularly shaped models. Typically mold rubber is sprayed or 

brushed on large models. Often, blanket molds are the only 

choice for large, immovable models (i.e., large gargoyle high on 

a building facade). 

With some models, blanket molds can be made in one piece and 

lifted or peeled off the model and subsequent castings like a 

sock; this is sometimes called a “glove mold.” A bas relief or a 

figure with a pyramid shape (the bottom wider than the top) lend 

themselves to one-piece molds. Molds that are to be turned back 

on themselves and peeled off must be kept thin, usually less than 

1/8-inch thick, to minimize stress and possible tearing of the 

rubber. As the mold is peeled off, it may need to be lubricated 

with silicone release or soapy water on the outside surface to 

allow it to slide easily against itself. 

For many types of models, the blanket mold must have a split 

down one side to allow for easy removal of the model and to 

reduce the chance of tearing the mold. The rubber at the end of 

the seam may be reinforced with fabric at the top where a tear 

may be likely to develop in the mold. 

For complex models, blanket molds can be made in two or more 

pieces. Shims or flanges are used to create seams or “parting 

lines” where required on blanket molds and their shells. A split 

blanket mold can be made by affixing a thin shim of aluminum 

flashing, cardboard or stiff plastic film to the model projecting 

several inches, applying release, and brushing/spraying the 

rubber up against the shim. The shim should have keys or 

indentations to allow the rubber flanges of each mold section to 

THIXOTROPY: 

The key to successful brush-on molds. 

Thix.ot.ro.py \thik-`so-tr -pe\ n [fr. Gk thixis 

act of touching]: the property of various gels 

becoming more fluid when disturbed (as by 

mixing) -- thixotropic adj 

(Webster’s Ninth New Collegiate Dictionary) 

e 

One-piece, Polygel ® brushed blanket mold. 

lock together to maintain position with respect to one another 

and to the shell. 

With the development of self-thickening and “thixotropic” (see 

definition below) mold materials, making brush-on and sprayed 

blanket molds has become routine. Not only do brush-on and 

spray molds use less rubber, but they are generally faster to 

make than poured blanket molds and offer the moldmaker visual 

control of rubber placement. 

In the past, blanket molds were often made by dipping the model 

into or brushing on latex. Since each layer of latex must dry 

overnight before the next layer can be applied, building up an 

adequate thickness of latex for a useable mold can take weeks. 

Trying to brush-on a pourable liquid without thickening usually 

produces less than satisfactory results since the the liquid flows 

off vertical surfaces. In order to make molds faster, moldmakers 

add fillers to pourable mold rubbers in order to thicken the 

uncured mix to a consistency that can be applied by brush. For 

example, Poly 74-30 Liquid Mold Rubber can be mixed with 

fumed silica (i.e, Cab-O-Sil ® ) to make brush-on blanket molds 

(see photograph on p. 21). Many customers use this method 

because it allows them to thicken the rubber to the exact 

consistency that is desired and is the most economical method of 

making brush-on molds. For more information regarding 

thickening of liquid mold rubbers, refer to the product 

descriptions (see pp. 34-45) or call Polytek Customer Service. 

In 1992, Polytek received a patent for the Polygel ® technology, 

which enables the mixed Parts A and B liquids to immediately 

react to form a gel with a consistency perfect for brush-on 

application. Polygel 35, 40 and 50 Liquid Mold Rubbers are 

ideal for brushing on a properly prepared model right after Parts 

A and B are mixed. In addition, certain Polygel products have 

been specially formulated for spray application (Polygel Spray 

35, Polygel Spray 50 and Quick Spray 50). See pp. 36-37 for 

information on Polygel products. 

Whether using liquid rubber thickened with Cab-O-Sil or the 

advanced Polygel products, a most important characteristic of 

the mixed mold material for brush-on or spray application is 

“thixotropy” (see box). To make a brush-on or spray-on blanket 

mold, the rubber must be thick enough to not sag after 

8 

(610)559-8620 • (800)858-5990


Both brush-on and spray blanket 

molds are most easily made with 

Polygel ® Liquid Mold Rubbers. 

application on the model, but also must be more fluid when it is 

mixed or moved around the model surface with a brush. Polygel 

products are thixotropic: they are thick enough to resist sagging 

when applied to a vertical surface, but are fluid when mixed and 

moved around the model surface. Basically, the more energy you 

put into a thixotropic material, the lower the viscosity -- the 

faster you stir it the more fluid it seems. A good liquid rubber for 

brush-on molds must become thixotropic shortly after Parts A 

and B are mixed together -- that’s Polygel. 

For diagrams depicting the procedures to make a single-piece 

blanket mold, a split single-piece blanket mold, and a multipiece 

blanket mold, see pp. 18-23. 

MOLD SHELLS (AKA “MOTHER MOLDS”) 

A mold shell, also known as a “mother mold,” is not a 

production mold but rather a shell that is required to hold the 

flexible rubber mold in its proper shape. The shell and mold are 

used on the production line. Mother molds are sometimes used 

with block molds and are nearly always used with flexible 

blanket molds. Mother molds can be made of plaster, plaster and 

hemp, polyester resin and fiberglass, urethane foam, or one of 

Polytek’s firm liquid rubbers or rigid liquid plastics. Poly 15 

Series Liquid Plastics (15-6, 1511 and 1512X) and Polygel 

Plastic-75 make tough, durable, lightweight mold shells in a 

matter of minutes! For more information on 15-Series Liquid 

Plastics see p. 49; for Polygel Plastic-75, see p. 55. 

The mother mold is usually made over and is removable from 

the rubber production mold. Care must be taken so that a rigid 

shell does not lock onto undercuts in the block or blanket mold. 

All such undercuts must be eliminated or the shell must be made 

in multiple pieces to work around them. In certain situations, a 

firm but flexible mother mold can offer a good solution to 

undercuts. A flexible mother mold, such as one made of Poly 

74-30 Mold Rubber, can be pulled off simple undercuts. You 

may use a little more rubber, but you can save lots of labor. 

Mother molds are often two or more pieces even when the mold 

is one piece. The shell for a split mold would part along the line 

of the split in the mold. Parting lines for shells can be 

established using plasticene strips applied to the cured rubber, 

building up the shell against one side of the strip, removing the 

strip, applying release and building the other half of the shell. 

When complete, the sections of the shell press the flanges of the 

rubber together like a gasket, keeping the parting line tight and 

inconspicuous. If a brush-on mold is large, the rubber should 

have projecting keys or 

rubber “snaps,” on its flange 

and back so that the mold 

locks into the shell to 

prevent flopping out of 

position. [Tip: Buttons of 

rubber, cast in advance in 

plastic pill holders, can be 

bonded onto the last coat of 

the mold rubber so that the 

shell is formed around them 

holding the mold in position 

in the shell.] 

In the case of a poured 

blanket mold, the mother 

mold is typically made 

before the rubber mold is 

made. After the mother mold 

is cured, it is positioned over 

the model and the liquid 

mold rubber is poured into 

Polygel ® rubber mold and resin 

shell made of Poly 15-6 Liquid 

Plastic thickened with Poly Fiber. 

the void between the mother mold and model to make the 

blanket mold. For more on this technique, see pp. 22-23. 

A mother mold can last indefinitely and can help prolong the life 

of a mold since a rubber mold stored in its shell can maintain 

exact dimensions. The mold in its shell will last many years if it 

is stored in a cool, dry area out of sunlight. Still, when the 

rubber fails (as all flexible molds eventually do) the shell is 

simply repositioned over the model and a new mold is poured, 

ready for use the next day. 

These three photos 

illustrate the construction of 

a poured blanket mold. 

First, the model, a gargoyle 

face, is covered with clay. 

Next, a rigid, plastic mold 

shell (i.e., Poly 1512X, see 

p. 49) is constructed over 

the clay blanket. After the 

plastic cures, it is removed 

and the clay is removed 

from the model. Then the 

plastic shell is repositioned 

over the model and liquid 

rubber (i.e., PlatSil ® 71-11, 

see p. 43) is poured through 

an opening in the shell and 

covers the model. Once the 

rubber cures, the model is 

removed and the mold is 

ready to use. Cast away! 

Mold Making 

Methods 


9


Mold Making 

Methods 

TYPES OF CASTINGS 

There are numerous types of castings and casting methods. 

Castings vary by the type of material that they are made of (see 

p. 2), and by the method employed to make them. The table 

below summarizes the most common casting methods along 

with the advantages and disadvantages inherent in each 

technique and the products for which one might use each 

method. 

The photo to the right shows numerous castings made from 

various Polytek casting plastics. 

Casting Method Advantages Disadvantages End Uses 

Solid Pour 

Material is poured into the mold 

resulting in a solid casting. 

Gel Coat and Layup 

A thin surface coat is applied and 

subsequent layers of reinforcing 

material like fiberglass mat and 

resin are built up to a thin, strong 

laminate. 

Slush Cast 

Material is manually rotated in the 

mold creating a thin layer resulting 

in a lightweight hollow casting. 

Rotational Cast 

A closed mold is rotated by 

machine as a small amount of 

material coats the surface and sets, 

resulting in a hollow, lightweight 

casting. 

Injection 

Liquid is forced into the mold 

under pressure. 

Fast Heavy Small objects 

Possible high cost 

Industrial tools 

Lightweight Time consuming Rigid molds 

Less material used 

Mold shells 

High quality surface 

Large objects 

Bonded bronze 

Lightweight Time consuming Art objects 


Bonded bronze 

Fast Need a machine Larger statuary 

Easy 

Hollow parts 

Lightweight 

Six-sided parts 

Quality parts Requires setup time Manufactured parts 

Often need a machine 

Vacuum and Pressure 

Bubbles are eliminated, resulting 

in perfect, high detail parts. Used 

in conjunction with solid pour. 

Direct Layup/Spray - No Mold 

Material is spread over a screen 

armature. Surface detail is sculpted into 

the wet material or plastic hardcoat 

sprayed over carved foam substrate. 

Quality parts Requires setup time Prototypes 

Need vacuum pump/pressure pot Figurines 

Lightweight Time consuming Amusement/theme parks 


Sculpted rocks 

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MOLD MAKING PROCEDURES 

This section guides you from model preparation through 

finishing your casting. The directions provided here are general 

in order to be helpful regardless of what mold making and 

casting materials you choose and what type of mold or casting 

you’re making. The following sections are presented in the order 

that your project should proceed. Diagrams that depict 

procedures for making a few different types of molds are 

presented after the complete text description (see pp. 17-23). 

SAFETY FIRST! 

Before you even open your containers of mold making or 

casting materials, understand the hazards of the materials that 

you’ll be working with. 

• Read material safety data sheets (MSDSs) and 

product labels - MSDSs are sent with every Polytek 

product and contain very important safety information. 

Also, Polytek product labels have hazard warnings and 

precautionary statements. Read the MSDS and labels 

carefully so that you can use Polytek products safely. If you 

do not receive MSDSs with your shipment, call Polytek 

Customer Service and they will promptly get them to you. 

• Understand health hazards - Some uncured Polytek 

products can cause skin, eye and respiratory irritation if 

improperly handled. Also, a few uncured products can 

cause dermal and respiratory sensitization (i.e., allergic 

reactions) in sensitive individuals. Avoid skin and eye 

contact and breathing vapors from uncured materials. Do 

NOT use Polytek products where food or prolonged body 

contact may occur. 

• Use personal protective equipment (PPE) and 

engineering controls - Follow recommendations on 

product MSDSs for use of PPE such as gloves, dust masks, 

safety glasses or goggles, aprons, and, in limited cases, airpurifying 

respirators with organic vapor cartridges. Use 

products in areas with adequate ventilation such as a large 

open room with air circulation. 

READ DIRECTIONS 

All too often, projects are spoiled because, in enthusiasm for 

completing a project, important directions are not followed. 

Before starting your project, read product technical bulletins and 

label directions thoroughly. Call Polytek Customer Service if 

you have any questions. 

MODEL PREPARATION 

Porous models, such as wood, plaster, stone, pottery or 

masonry, must be sealed, then coated with a release 

agent such as Pol-Ease ® 2300 Release Agent or PolyCoat. 

Sealing prevents rubber or resin from penetrating pores in the 

model surface. Several coats of paste wax, allowed to dry and 

polished or melted paraffin, petroleum jelly, lacquer, shellac, 

If you don’t follow directions ... 

there is a lot that can go wrong ... 

• Improper Mix Ratio - Slow, non-curing or 

soft material can result if two-part materials are 

not weighed or measured accurately. Always use 

an accurate scale (see accessories, p. 63). Do 

calculations carefully and double check the mix 

ratio listed on labels and product literature. 

• Release Agent or Sealer - Incorrectly 

applied or missing, or use of the wrong sealer or 

release can result is sticking or damage to the 

mold/casting. If you’re not sure that you’ve 

properly sealed/released a model, make a test 

cure. Too much release agent can cause pinhole 

surface defects or bubbles in the mold and/or 

casting. 

• Low Temperatures or Demolding Too 

Soon - Deformed parts can result. Fluctuating 

temperatures during curing can cause bubbles and 

dimensional changes. 

• Leaking Mold, Boxes or Shells - Your pour 

can spill, wasting material and time. Use 

mechanical fasteners and hold downs and be sure 

that seams are tight and sealed. 

• Material Hardens Before It’s In Place - 

Avoid delays once material is mixed. Watch a clock! 

• Unmixed Material - Streaks of uncured or 

soft areas and/or gas bubbles can develop several 

weeks after curing if Parts A and B are not 

thoroughly mixed. Poorly mixed material is often 

from the sides and bottom of the mixing container. 

• Incorrect Material Selected - Choosing 

the wrong material can result in sticking or 

damage such as staining or softening a model, 

mold or casting. 

• Material Not Stirred Before Use - Some 

components (Part A or B) must be stirred before 

use. If the component is not carefully stirred 

before mixing with its counterpart, soft cures or 

bubbles can result. 

• Contaminated Material - Moisture or 

other foreign contaminants can spoil the cure of 

materials. Freshly opened containers and clean 

tools are important. 

Mold Making 

Methods 


11

Mold Making 

Methods 

12 


Important Terms 

Cure time is often longer than demold time, sometimes even 

though a product feels cured and can be demolded, curing may 

continue for up to a week. 

Demold time is the soonest a cured product can be removed 

from the mold if it has been at recommended temperature. 

Demolding castings as soon as possible helps to extend mold 

life. Thin castings may require more time in the mold before 

demolding. 

Density is the weight of material that fills a given space. Water 

has a density of 1.0 g/cc and a pound of water takes up 27.5 

cubic inches. Thus a pound of material with a density of 2 g/cc 

will only fill half the space or 13.75 cubic inches. When buying 

mold rubber or casting resin you must consider the price per 

volume, as the price per pound can be misleading. (See box on 

“Cost per cubic inch,” p. 4.) 

Elongation, reported in percent, is the length the material 

stretches before breaking. 

Hardness is measured with a Durometer. It pushes a needlelike 

probe into the rubber as it is pressed against it. The 

farther the needle penetrates into the sample the lower the 

reading. The Shore A scale is used for rubbers and the Shore D 

scale is used for plastics. Both scales go from 0 to 100. A 

rubber with a Shore A hardness of 0 is like warm chewing gum. 

Shore A10 to 20 is about as soft as any mold rubbers can be. 

Shore A50 rubber is like a car tire. Above A80, rubbers feel 

more like a plastic and may measure on the low end of the 

Shore D scale. Shore D90 is about as hard as plastics get. 

Pour time, working time, pot life or gel time give you an idea 

how much time you’ll have to work with a material from the time 

mixing begins until it gels. Most materials should be in place 

well before the end of this time to allow good flow into detail 

and for air bubbles to rise and break. 

Rheology describes how a liquid flows. A liquid is Newtonian if it 

flows and levels, even if very slowly. Pourable mold rubbers 

should be Newtonian. Brush-on mold rubbers may be 

thixotropic, that is they flow when brushed/troweled, but when 

undisturbed they stay where they are placed (see box on p. 8). 

Shrinkage is a reduction in size, which occurs with some 

plastics during cure or some rubbers after prolonged use. 

Casting materials draw oily materials out of the rubber causing 

it to shrink. Products that develop heat during cure shrink as 

they cool. The degree of shrinkage increases with the 

temperature increase during cure. Some plastics get warmer in 

the center than against the cool mold surface and tend to 

cause the still liquid resin against the mold to sink. (See box on 

“Exotherm,” p. 6.) Polytek products that stay cool during cure 

do not shrink while curing. 

Tear strength is reported as the force needed to tear a split 

one-inch long in a piece of material. Higher elongation rubbers 

generally have a higher perceived tear strength. 

Tensile strength is the force required to break a piece of 

material when pulled. It is reported in pounds required to break 

a one-inch square specimen of material. 

Viscosity, reported in centipoise (cP), describes if a liquid is 

thick or thin. Water is low viscosity (1 cP), while pancake syrup 

is higher (1000 cP), and honey is even higher (10,000 cP). 

Temperature affects viscosity -- the lower the temperature, 

the higher the viscosity. For best flow into detail, Polytek 

materials should be at least room temperature. 

paint, PVA (polyvinyl alcohol solution), and potters’ soap on 

plaster all work well for certain surfaces and mold rubber or 

resin combinations. Some rubbers (i.e., Poly-Fast 72-40) contain 

materials that dissolve or soften lacquer and paints. For them, 

wax or shellac are often used as sealers. Polyurethanes bond 

tenaciously to shellac, however, so if shellac is used as the 

sealer, release agent must be very carefully applied over it. 

Bare plaster is best sealed with potters’ soap (or Murphy’s Oil 

Soap) lathered into the damp surface of the plaster with a soft 

brush, rinsed and repeated several times, then polished with a 

soft brush or cloth. Only use soap on plaster, it is not suitable for 

sealing with other materials. If the plaster is dry, it should be wet 

for several seconds under running water prior to soaping. 

Moist water clay, another special case, can be sealed and 

released with Pol-Ease 2350 Release Agent or by spraying on a 

10% solution of petroleum jelly in mineral spirits, made by 

warming and melting the petroleum jelly and stirring in mineral 

spirits. [Note: Use extreme caution since mineral spirits is highly 

flammable.] Then apply the solution using a plant spray bottle, 

brush out and allow to dry. This prepares the water clay for 

contact with most mold rubbers. If the water clay is completely 

dry, it should be sealed and coated with release as for terra cotta. 

Pol-Ease 2300 Release Agent must be applied to nearly 

every surface before pouring or applying liquid rubber (except 

silicones) or resin. It should be sprayed evenly and then gently 

brushed out with a dry brush to pick up any excess and to spread 

the release over any spots missed by the spray. The brush should 

be wiped with a paper towel periodically to prevent too heavy a 

coating being left on the surface. Too much release can cause 

pinhole defects in the surface of the liquid material poured 

against it. The coating of release should be allowed to dry for 

about 15 minutes prior to pouring. Silicone-based release agents 

like Pol-Ease 2300 may interfere with the cure of silicone mold 

materials. When pouring silicones, use Pol-Ease 2350 on 

surfaces that the liquid silicone will contact. Consider PolyCoat 

as a semi-permanent, dry sealer and release when using 

polyurethane rubbers. 

If you have any question about the compatibility 

between the rubber and the prepared model surface, 

perform a test cure on an identical surface to determine that 

complete curing and good release are obtained. Some materials 

such as sulfur-containing modeling clays and wood knots, inhibit 

curing of some rubbers and plastics. 

Securely fasten and seal side boards or shells to the 

base to prevent leakage. Seal and apply release on all side 

boards and shell interiors. Petroleum jelly is excellent for most 

non-critical surfaces like these, unless the material gets warm 

enough during cure to melt the petroleum jelly. Pol-Ease 2300 

Release Agent is more heat resistant, but is not self-sealing, so 

surfaces must first be well sealed. 

Porous models must be vented from beneath to prevent 

trapped air from forming bubbles in the rubber. A hole at least 

¼-inch in diameter should be drilled through the base board into 

the porous model. The base of the model must be sealed around 

the perimeter with Poly Plasticene or glue to prevent liquid 

rubber from leaking under the model and through the vent hole. 

(610)559-8620 • (800)858-5990


MIXING THE MOLD RUBBER 

Have all materials at room temperature (75°F) before 

mixing. It can take 24 hours for a 5-gal pail of material to warm 

up to room temperature in the winter. 

Have all materials and equipment clean and ready. 

Time is critical to success. You do not want to go searching for 

tools after you have mixed Parts A and B. 

Stir individual components before use if recommended. 

Some materials separate and will not cure properly if separated 

material is used. 

Weigh and measure accurately. Mix Ratios Vary! Check 

the mix ratios for the specific product you are using. For liquid 

rubbers, most mix ratios are expressed by weight. Carefully 

weigh Parts A and B in proper ratio. Weighing components on 

an accurate scale is a must. Only materials with a mix ratio of 

1:1 by volume can be measured by volume. Polytek does not 

recommend trying to measure any other mix ratio by volume. 

Close containers tightly after use. Most materials are 

usable at least six months to a year after shipment if unopened. 

Uncured polyurethanes, epoxies and some silicones react with 

atmospheric moisture and, therefore, should be used up as soon 

as possible after opening. Before resealing, Poly Purge Dry Gas 

Blanket (see p. 63) can be sprayed into open containers to 

displace moist air and extend storage life. 

Time your actions with a clock. Start timing when you start 

mixing. Try to have material poured and in place before half of 

the working time has elapsed so there is plenty of time for 

bubbles to rise away from the mold surface. 

Mix well, but avoid whipping air into the mix. Scrape the 

sides and bottom of the mixing container thoroughly several 

times while mixing. A Poly Paddle is invaluable for good 

mixing. Sometimes, to insure that no unmixed material is 

clinging to the sides or bottom, the mix can be poured into a 

clean container and mixed again for 1 to 2 minutes before 

pouring. For large mixes (i.e., >30 lb), a Jiffy Mixer (see p. 62) 

on a variable speed drill can be helpful, but care must be taken 

not to whip air into the mix or scrape the jiffy mixer blade 

against sides and bottom of the container. 

Avoid being rushed. Careful 

planning allows for a deliberate 

pace without making mistakes. 

Before starting to mix rubber, have all materials at hand 

and at room temperature (75°F). 

A Poly Paddle is an 

excellent tool for handmixing 

liquid rubber without 

introducing excess air into 

the mix. Scrape the sides 

and bottom of the mixing 

container thoroughly 

several times while mixing. 

Carefully Adhere to Mix Ratios! 

The chemistry of polyurethanes, 

silicones, and epoxies must add up. 

Unlike polyester resins, the recommended mix ratio 

of polyurethanes, silicones, and epoxies cannot be 

varied without causing changes in the physical 

properties of the cured material. This is because to 

cure 100 reactive groups of Part A, 100 reactive 

groups of Part B are needed. If 100 reactive groups 

of A weigh two pounds and 100 of B weigh one 

pound, then the mix ratio must be two A to one B 

(2A:1B), by weight. 

Generally, if excess B is used the cured plastic will 

be softer. If excess A is used the plastic will be 

harder. But off-ratio mixes can cause other 

problems, such as no cure at all, dimensional 

instability, or short storage life of the cured rubber. 

Mold Making 

Methods 


13


Mold Making 

Methods 

APPLYING THE MOLD RUBBER 

Most often liquid mold rubber is poured over the model surface. 

With the development of Polygel products, however, applying 

liquid mold rubber to the model surface by brushing or spraying 

is becoming increasingly common. No matter how the liquid 

rubber is applied, one key is to avoid air entrapment. For poured 

molds, the liquid rubber should be poured in a steady stream 

into one corner of the mold box, allowing the liquid to flow over 

the model surface pushing air out ahead of it. In some cases, 

where there is exceptionally fine detail, some moldmakers feel 

that applying a small amount of mixed rubber to the surface and 

brushing or blowing it into the detail with low pressure air 

before pouring the bulk of the mix helps to ensure that the liquid 

pushes all the air out of the crevices. Caution must be taken that 

brushing does not actually push the liquid through the film of 

release agent on the surface, causing sticking, or that release 

does not float to the top of the brushed liquid, preventing 

Mold rubbers are typically applied 

to a model by pouring, brushing, 

or spraying. Liquid mold rubbers 

with thixotropic properties are 

ideal for brush and spray 

application. Think Polygel ® . 

How Much Liquid Rubber Do You Need? 

Poured Block Mold - Box Shape 

1. Calculate the volume of the box in cubic inches (in 3 ). 

V = l x w x h where: l = Length 

w = Width 

h = Height 

e.g., 10 in x 5 in x 5 in = 250 in 3 

2. Estimate the volume of the model. 

e.g., 8 in x 3 in x 3 in = 72 in 3 

3. Subtract the estimated volume of the model from the 

volume of the box. 

e.g., 250 in 3 - 72 in 3 = 178 in 3 

4. Use specific volume data (refer to Technical Bulletin for 

specific product) to convert the volume to quantity of 

liquid rubber needed in pounds. 

e.g., Using specific volume of Poly 74-30 Liquid Rubber 

(27.5 in 3 /lb): 

178 in 3 ÷ 27.5 in 3 /lb = 6.5 lb Rubber 

Poured Block Mold - Cylinder Shape 

1. Calculate the volume of the cylinder. 

V= π x r 2 x h where: π = 3.14 

r = Radius (½ diameter) 

h = Height 

e.g., Using a 10-in tall section of 5-in diameter PVC pipe: 

3.14 x (2.5 in x 2.5 in) x 10 in = 196 in 3 

2. Estimate the volume of the model. 

e.g., 8 in x 3 in x 3 in = 72 in 3 

3. Subtract the estimated volume of the model from the 

volume of the cylinder. 

e.g., 196 in 3 - 72 in 3 = 124 in 3 

4. Use specific volume data to convert the volume to quantity 

of liquid rubber needed in pounds. 

e.g., Using the specific volume of Poly 74-30 Liquid Rubber of 

27.5 in 3 /lb: 

124 in 3 ÷ 27.5 in 3 /lb = 4.5 lb Rubber 

Note: For the hypothetical model above, far less liquid rubber is needed for the cylindrical mold. Choose your containment area carefully. 

Brushed/Sprayed Blanket Mold 

1. Estimate the surface area of the model. Depending on the 

complexity of the model, this can be difficult and it may be 

necessary to consider a model in sections and add up all surface 

areas. If the model is basically rectangular, use the surface area 

equation for a rectangle; if cylindrical use the surface area 

equation for a cylinder (A = 2πr 2 + 2πrh). 

2. Multiply the surface area by the thickness of the blanket mold 

(usually 0.25 in to 0.38 in) to determine the volume of liquid 

rubber needed. 

3. Use specific volume data to convert the volume to quantity of 

liquid rubber needed in pounds 


Poured blanket molds are usually made by covering a model with clay, 

making a shell, removing the clay, and filling the area once filled by 

clay with liquid rubber. Therefore, the volume of clay equals the 

volume of liquid rubber needed. Using the weight of the clay, calculate 

its volume by multiplying by its specific volume. Divide the volume of 

clay by the specific volume of the liquid rubber to get the weight of 

rubber needed. 

e.g., If a 2-lb block of clay was removed from the model: 

2 lb x 18.4in 3 /lb = 36.8 in 3 clay 

36.8 in 3 x ÷ 27.5 in 3 /lb * = 1.3 lb Poly 74-30 Rubber 

* Specific volume of Poly 74-30 Liquid Rubber 

14 

(610)559-8620 • (800)858-5990


adhesion between the poured material and the brushed material. 

For more information on applying liquid mold rubber by brush 

or spray, refer to Polygel product information (see pp. 36-37). 

If a super smooth mold back is desired, a light spray of Pol-Ease 

2300 Release Agent on the top surface of the liquid just before it 

gels breaks most of the surface bubbles. 

CURING THE MOLD 

Cure at the same warm temperature that all your materials were 

when mixed. Temperatures below 65°F lengthen the time 

required for proper curing and may spoil the cure of some 

materials. Placing the poured mold or casting in a warmer area 

than the materials were when they were poured, can cause 

problems because changing temperatures while the material is 

setting can cause bubbles or distortion. 

Check product technical bulletin for proper cure time. Demold 

carefully as the material is still more tender than it will be a few 

days later. Bending or forcing a material while it is still only 

90% cured can cause distortion that may not recover. 

USING THE MOLD 

More rubber molds fail due to poor handling than by wearing 

out. Proper design, careful handling and attention to detail 

prolong mold life. 

When casting plaster, wet the rubber mold with Pol-Ease Mold 

Rinse or a 1% detergent (e.g., Ivory Liquid) solution in water 

before pouring the plaster. Wet the mold by dipping or spraying. 

Pour the plaster on the wet surface. [Note: Detergent is 

chemically different from soap. Do not use soap -- Ivory Liquid 

is a detergent.] 

When casting plastics in polyurethane or silicone molds, first 

coat the mold with a release such as Pol-Ease 2300 Release 

Agent. Release agent is not always needed in silicone molds. 

Spray a light even coat of Pol-Ease 2300 on the mold surface 

and then carefully brush the surface with a clean, dry brush to 

pick up any excess and cover any missed spots. 

PVA is a barrier to migration of plasticizers and chemical attack 

by harsh casting resins. Poly-Fast 72-40 rubbers contain 

plasticizers that can soften resin surfaces producing soft or 

sticky castings. If resins are to be cast in 72-40 molds, first coat 

the mold surface with PVA and allow to dry, then lightly spray 

with an even coat of Pol-Ease 2300. This surface treatment 

often acts as a barrier to the plasticizers. PVA can be washed off 

castings with soapy water. PVA also prolongs the life of 

polyurethane molds when casting polyester resins. 

For long mold life, avoid exposing rubber molds to strong 

solvents, oils or cleaners. Sprayed release agents reduce solvent 

exposure as compared to brush application. 

STORING THE MOLD 

Proper storage of molds cannot be overemphasized and is the 

key to extended “library life” -- the time that a mold remains 

useful after storage. Some rubber molds, if stored properly, can 

have a library life of ten years or more. 

Store molds in their original, undistorted shape. Molds should 

be left in the mother mold, mold box or on a surface that causes 

the least distortion possible. If rubber is left in a distorted shape 

for any length of time it can take a permanent set and may never 

recover to its original shape. 

If a blanket mold is stored in a mother mold/shell made of 

porous material, such as bare plaster, the shell surface that 

contacts the mold must be sealed (e.g., with shellac). Sealing the 

shell prevents it from absorbing oils from the mold rubber 

which, in turn, can cause mold distortion. 

Do not allow molds made of one type of rubber to remain in 

contact with molds of other rubbers as migration of oils or 

plasticizers from one to another can cause swelling, shrinkage, 

or distortion. 

Poly-Fast 72-40 molds may soften over a period of 2-4 years. 

TinSil silicone molds may embrittle (i.e., lose tear strength and 

elongation) over a similar period. These mold materials should 

not be selected if long library life is required. 

Molds should be stored in a cool, dry area and out of the 

sunlight, which can degrade the surface. 

Colors for Polytek Products 

This blanket mold of a 

baluster is stored 

properly in its mold 

shell. The thin mold of 

PlatSil ® 73-45 is 

supported by a firm 

shell made from Poly 

75-80 Liquid Rubber. 

Most Polytek Liquid Rubbers & Plastics can be colored with 

the use of proper dyes or pigments. PolyColors, reactive liquid 

dyes available from Polytek in red, green, yellow, blue, brown 

and black, can be used in most Polytek polyurethane 

products. In addition, PolyColors can be added to certain 

silicones in small concentrations. Polyurethane rubbers and 

plastic can be lightly tinted or made vibrant and dark in color 

by using PolyColors up to 3% by weight of the total liquid mix. 

PolyColor Brown is excellent for creating a base color when 

making cold cast bronze parts. PolyColor Black can be used 

to make even the whitest plastics true black. Since PolyColors 

are dyes, not pigments, they mix in easily and do not settle in 

the liquid rubber or plastic when properly mixed. Use 

PolyColors individually or in combination to make any color 

imaginable. For product information, see p. 61. 

Mold Making 

Methods 


15


Mold Making 

Methods 

CASTING & FINISHING 

For simple solid casts, the flexible mold and shell (if required) 

are positioned so the opening is level and release agent, barrier 

coat or rinse is applied, if necessary. The casting material is 

poured right to the top edge, vibrated if necessary and allowed to 

cure. Most casts should be removed as soon as they are 

adequately set, since longer residence times can damage some 

mold materials. 

Use of vacuum or pressure (see box below), brushing, spraying 

or heated molds are all helpful techniques to eliminate bubbles 

and achieve perfect casts of highly detailed parts, but simple 

pours are often adequate. 

Trim and touch up, is easiest while the casting is warm and is 

best done just after demolding. Remove release agent prior to 

painting by detergent washing. If a prime coat is desired on the 

cast part, a barrier coat can be sprayed on the mold before 

casting. Paint enhances and protects plastic castings and is 

necessary for best exterior durability. 

CLEANUP 

Tools should be wiped clean with paper towels before the rubber 

cures. Casting plastics are extremely difficult to remove from 

tools once cured. Be sure to clean tools as soon as possible. 

Denatured ethanol is a good cleaning solvent, but it must be 

handled with extreme caution owing to its flammability and 

health hazards. Work surfaces can be waxed or coated with Pol- 

Ease 2300 Release Agent so cured rubber and plastic can be 

removed. 

VACUUM & PRESSURE CASTING 

Perfect Castings Made Easily! 

Although many excellent bubble-free molds and castings are 

made with Polytek rubbers and resins every day, trapped air 

bubbles create the most common defects. Proper use of 

vacuum or pressure can eliminate bubbles from some kinds of 

castings and molds and is often cheaper and easier than you 

might think. The following applies only to non-porous molds 

and models -- porous materials such as wood and plaster do 

not lend themselves to use of vacuum and pressure. 

Vacuum 

Using vacuum to pull air bubbles out of mixed liquid rubber or 

resin can often be very helpful. Place the container of mixed 

liquid rubber or resin in a vacuum chamber and draw about 28 

inches mercury so that the largest air bubbles rise to the 

surface. You must perform degassing while the mix is still 

liquid. Do not attempt to “vacuum degas” Polytek rubbers or 

resins with short work times -- this can result in creating more 

bubbles. Some liquids rise 2 to 3 times their original volume 

during degassing, so use a container with adequate head 

space. Once degassed, the liquid should be poured carefully so 

that air is not reintroduced into the mix. 

Simple vacuum chambers can be constructed from pressure 

pots as well as from sturdy commercial cooking pots. It’s best 

to have a transparent cover. Vacuum pumps can be purchased 

from laboratory equipment dealers. A vacuum pump that is too 

small with insufficient capacity can be a frustration. You may 

find your material gelling before it is free of bubbles. Buy a 

large enough vacuum pump that will get down to maximum 

vacuum quickly so you can degas and pour before your mixed 

material thickens or gels. A Welch Model 1397 can often be 

purchased from equipment dealers for ~$3,000 new or ~$1,500 

used. It pulls 17.7 CFM and works well with a 40-quart pot. 

An alternative to a traditional vacuum pump is a venturi vacuum 

pump from Vaccon Vacuum Products. This device is attached to 

a vacuum chamber and an air compressor. The high volume air 

from the compressor flows past the double venturi, creating a 

negative pressure area, which in turn evacuates the chamber. For 

some applications, the venturi pump is a less expensive and 

effective option. For more information, go to www.vaccon.com. 

Pressure 

Using pressure to eliminate bubbles can be even more useful. 

The process is like reversing the opening of a bottle of soda. 

When pressure is applied to liquid rubber or resin, small 

bubbles are forced into solution and disappear. To accomplish 

pressure casting, pour the resin or rubber and place the whole 

mold in a pressure pot before the material begins to set. Fasten 

the lid and pressurize to ~60 psi with compressed air or 

nitrogen. Allow the cure to take place under pressure. You will 

be amazed with the results. 

Inexpensive pressure pots typically used by spray painters are 

available from paint supply stores and industrial supply houses 

such as Grainger. 

Caution: Vacuum and pressure systems can be dangerous. If 

you have any questions about the construction or operation of 

your vacuum or pressure system, consult a qualified engineer. 

Never use glass parts 

unless they are 

certified for the 

purpose. 

Welch Model 1397 vacuum pump with 

a 40 quart pot and lid made with 

Poly-Optic ® 1410 Clear Casting Resin. 

16 

(610)559-8620 • (800)858-5990


POURED MOLDS 

One-Piece Block Mold 

To make a poured block mold the model must be securely 

fastened (e.g., screwed or glued) to a base board. Kitchen 

countertop sink cut outs make excellent base boards. If the 

model is porous, a vent hole should be drilled through the 

baseboard to the model to allow air to escape. Sides of the mold 

containment area must be positioned and sealed to the base 

board (e.g., with plasticene or hot melt glue) so that liquid 

rubber cannot leak out. If the mold will be used without being 

placed in a box for support, then be sure to position the sides far 

enough from the model such that the rubber mold will be thick 

enough that it will not deform when it is full of casting material (at 

least 0.5-inch thick). Sometimes a strap is placed around the finished 

mold box to ensure that it all holds together. Once the model and the 

Screw model to base 

Poured mold rubber 

Sealed and released model 

Vent hole 

base and sides of the box are properly sealed and released, slowly 

pour liquid rubber directing the flow to the bottom of the box and 

being careful not to trap air bubbles as the liquid rises. The rubber 

should be at least 0.5 inches above the highest point on the model 

(mark the mold box before you start pouring liquid rubber). 

Mold Making 

Methods 

Cut Block Mold 

A block mold can be cut when cured to make a split or multipiece 

mold. With some models, the mold must be cut to allow 

for removal of the model. Sometimes the cut is simply a single 

slit up one side of the mold, while in other cases a single-piece 

block mold can be cut into multiple pieces to create a complex 

multi-piece mold. In either case, after the model is removed, the 

mold is reassembled by carefully lining up the seams and 

usually returned to its box to hold it together before casting 

material is poured into the mold. 

For a successful cut block mold, the key is in the cutting. First, 

select a rubber with an appropriate hardness for cutting (i.e., 

Poly 74-30, soft Shore A30). Next, carefully evaluate where the 

cut(s) will be made (i.e., possibly up the back of the head, not on 

the face) and how many cuts are required. The cutting locations 

should be decided before the mold rubber is poured, marked on 

the mold box and then transferred to the cured rubber mold. To 

cut the mold, use a mold key knife (see p. 62), which has a sharp 

blade with a groove that creates a tongue and groove effect in 

the cut rubber. This makes reassembling the mold with the 

seams properly aligned possible. Vents and pour holes can be cut 

or drilled into the cured rubber, or can be formed with rods or 

plasticene prior to pouring the rubber. When casting, cut block 

molds are reassembled and typically placed back into the 

containment area with the pour hole at the top for filling with 

casting material. 

Sometimes, block molds poured as one piece are the fastest to 

make even for oddly shaped models; but they require more 

liquid rubber than blanket molds. Making quality, multi-piece 

block molds requires considerable practice and expertise. 

Split Block Mold 

Rubber 


Model 

Mold 

Strap 

This head mold is 

cut from a cylinder of 

cured rubber. The 

containment area is 

a piece of PVC pipe 

sealed to a baseboard 

with plasticene 

or hot-melt glue. 

After the rubber 

cures, the pipe is 

removed from the 

base and cut with a 

saw to remove the 

mold. The rubber is 

cut with a mold key knife in a predetermined location to make a 

slit that allows for removal of the model. To avoid damaging the 

model, the first cut should not go completely though to the 

model, but rather the final cut through is made with a razor. 

When casting, the seam is carefully realigned and the mold is 

strapped together. The mold is inverted and casting material is 

poured into the opening. 

Multi-Piece Block Mold 

Chunk cut out to 

remove ears 

Chunk cut out to 

release front end 

Vent 

Plug cut out from between legs 

Split to remove tail 

This horse mold is cut from a single block of mold rubber. After 

pouring, curing and cutting the mold, it is reassembled and 

placed back into the mold box upside down for casting. Casting 

material is poured through the feet. As an alternative, the mold 

of the horse model could be made as a blanket mold poured into 

a pre-constructed shell -- this would mean easier cutting of the 

thinner blanket mold and using less mold rubber. 

17


Mold Making 

Methods 

POURED MOLDS (CONT’D) 

Block Mold Poured in Two Pieces 

A block mold can be made by pouring two pieces of the mold 

separately. First, one portion of the model is embedded in clay 

up to the desired parting line. Then liquid rubber is poured over 

the properly prepared, exposed portion of the model (1). After 

the rubber cures, the clay is removed and release agent is applied 

to the other side of the model and the cured rubber surrounding 

it. Rubber is then poured over the second half of the model (2). 

Once cured, a pour hole is cut through the rubber mold and, if 

necessary, vent holes are drilled through high spots in the mold 

to eliminate the possibility of trapped air bubbles. The mold is 

repositioned in its box and is ready for casting (3). 

1 

First pour 

3 

mold rubber 

clay 

vent pour hole vent 

2 

Ready for second pour 

Mold ready for 

casting 

positioning key 

mold rubber 

BLANKET MOLDS 


Generally, to make a poured blanket mold, the model is covered 

with clay and the mold shell is built over the clay-covered 

model, then the clay is removed and the liquid mold rubber is 

poured in the void left by the clay. 

First the model must be properly prepared (e.g., sealed and 

released) and mounted. Then the model is covered with plastic 

wrap to protect it before the clay is applied. The clay blanket is 

formed around the model and must fill-in any undercuts so that 

the mold shell cannot lock to the rubber mold. Since the shell is 

often made in two (or more) pieces, the clay is formed with 

protruding flanges, which act as parting lines for the shell. In 

fact, since the rubber replicates the clay blanket exactly, parting 

or cut lines should be delineated in the clay for transfer to the 

rubber. Sometimes “snaps” are placed along the clay blanket so 

that the rubber mold will “snap” into position in the mold shell. 

Cover the model with clay, then build the mold shell. 

The shell is made overtop of the clay usually by brushing on 

liquid plastic. Plastic mold shells are lightweight and durable 

and are typically made of Polygel Plastic or another liquid 

plastic (e.g., 15-6 or 1512X) thickened with an additive (e.g., 

Poly Fiber, see p. 61). The first section of the mold shell is built 

up against the clay flange. When the first section of shell is hard, 

the clay flange is removed, wax and then release is applied to 

the edge of the first shell section and the second section is built 

against the first section for a perfect keyed fit of the shell 

sections. 

To make the rubber mold, the clay and plastic wrap is removed 

from the model and then rubber is poured into the shell filling 

the void left behind. The rubber mold can be poured in one piece 

and cut with a mold key knife after curing. Or, for a two-piece 

mold, half of the clay is removed and rubber is poured in the 

void along half of the model. After the rubber cures, clay on the 

other half is removed, release is applied to the model and cured 

rubber, and liquid rubber is poured into the void along the 

second half of the model (see story with photos on pp. 22-23). 

Then pour liquid rubber into the shell. 

Shell 

(1st half) 

Clay 

Clay flange 

with groove 

Snaps 

Shell 

Clay plug 

to make 

pour hole 

in shell 

Liquid rubber 

Mold strap 

Shell parting line 

Vent 

Model 

Vent 

The prepared model is protected with a covering of plastic wrap 

and then a clay blanket (~0.5-inch thick) is built over the model. 

The shell is made over the clay by brushing on liquid plastic. The 

shell plastic is first applied to one half and cured. Then the clay 

flanges are removed and release agent is applied to the exposed 

plastic and the second half of the shell is built up to the first half. 

After the clay is removed, liquid rubber is poured into the void. 

When making a one-piece or cut mold, all of the clay is removed 

and the entire space is filled with rubber. If necessary, the cured 

rubber is cut to remove the model. 

18 

(610)559-8620 • (800)858-5990


Brush-On Blanket Mold 

A brush-on blanket mold is made first, then the shell is made 

over top of the cured mold for support. Some one-piece blanket 

molds are simply peeled off a low-relief or pyramid-shaped 

model (“sock” mold). But, often it is necessary to create a seam 

or cut a split in the mold to allow for removal of the model and 

castings. To create a parting line in the blanket mold, thin shims 

(e.g, aluminum flashing or stiff plastic sheet) are positioned on 

and securely fastened to the model. In lieu of shims, rubber can 

be brushed thick enough in areas so that the cured rubber can be 

cut to permit demolding. This technique is helpful for masters 

with “through holes” that can lock the rubber mold to the master 

(see pp. 20-21). 

If needed to prevent trapping air bubbles during casting, vents 

are formed in the mold by neatly fastening thin straws or rods to 

the model. Remember, neater fastening means less cleanup of 

the casting. After the model, shims and vents are coated with 

release, liquid rubber is brushed on. 

Sometimes with large models, it’s a good idea to create “snaps” 

or keys on the rubber mold to hold the mold in place in its shell. 

The shell may need to be more than one piece in order to allow 

removal from the rubber blanket mold. There can be no undercuts 

Dealing with Undercuts 

When making a brush-on blanket 

mold, all undercuts in the model 

must be eliminated before the mold 

shell is made. Typically, undercuts 

are filled with mold rubber or another 

filler material -- even air. Sometimes 

the filler must be compressible so that 

the mold can be removed from the 

model. A hollow bladder can be 

formed by bridging the undercut area 

with a piece of plastic wrap pressed into the previous layer of 

rubber. Then another coat of rubber can be brushed overtop of 

the plastic wrap. If more support is needed. the undercut can be 

filled with a material such as soft foam then covered with liquid 

rubber. 

In lieu of filling undercuts, a flexible mold shell can be built 

instead of the standard rigid mold shell. A flexible mold shell 

(e.g., made of Poly 74-30 rubber) can be removed from simple 

undercuts in the blanket mold and can sometimes alleviate the 

Rigid shell 

Flexible 74-30 

mother mold 

Brush-on 

mold 

Brushed-on rubber 

Model 

Filled 

space 

need for a multi-piece shell. 

A soft, polyurethane rubber 

(e.g., Poly 74-30) can be 

poured over a release 

coated blanket mold 

enclosed in a simple box or 

rigid mold. Although this 

option may be more 

expensive since it uses 

more rubber, it can save on 

labor. 

in the rubber mold that can lock the shell onto the rubber when 

there is a casting/model inside the mold (see box). 

The parting line for the rigid shell is defined with a clay (i.e., Poly 

Plasticene) flange applied over the mold. A groove or depressions 

should be made in the clay where it contacts the shell material to 

create good locking and positioning of the shell halves. The mold 

shell is built one section at a time against the release coated rubber 

mold and clay flange. When one section of the shell is complete, 

the clay is removed, Vaseline or butcher’s wax is applied to the 

exposed shell followed by a release agent, and the next shell 

section is built against the first. The two halves of the shell 

compress the rubber flanges along the mold opening together 

making a good seal so that liquid casting material cannot leak out. 

First, the model is prepared for making the blanket 

mold. Then thixotropic mold rubber is brushed on. 

Shims 

Vent 

The model is prepared (i.e., 

sealed and released) and 

securely mounted to a base. 

A vent is drilled through the 

base to release air trapped 

in the model. Thin shims are 

placed along the model and 

in spaces formed under the 

legs and arms. The shims 

form a parting line in the 

brush-on rubber blanket 

mold. Once the shims are 

secure, the rubber is 

brushed on in several coats 

to ¼- to ½-inch thick. 

After the rubber cures, the rubber-coated model is 

prepared for construction of the mold shell. 

Clay Flange 

Snaps 

Rubber-Covered 

Model 

A clay flange is formed 

around the model to define 

the parting line of the rigid 

mold shell. Depressions are 

made in the clay that will 

form “snaps” in the mold 

shell to help properly lock 

the mold shell halves 

together. In addition, rubber 

snaps can be placed on the 

rubber mold so that the mold 

snaps to the mold shell. The 

first half of the rigid mold 

shell is built up to the clay 

flange. Then, the clay is 

removed and the second half 

of the shell is constructed. 

When complete, the two 

halves of the shell compress the rubber along the mold opening 

to make for a good seal along the mold opening. 

Mold Making 

Methods 


19

Mold Making 

Methods 


Procedures - Brush-On Mold 

Making a Brush-On Blanket Mold with a Plastic Shell 

The following example details the procedures involved in 

making a brushed mold. The rubber that has been chosen is 

Poly 74-20, a soft, stretchy, 1A:2B by weight mix ratio, 

polyurethane liquid mold rubber. Of course, there are many 

variations to this technique and several choices of rubbers. We 

could have chosen to make a one-piece brushed mold with 

shims similar to what is shown on page 19. We just as easily 

could have made a two-piece mold where we need no cuts to 

remove two separate halves of the rubber mold. 

This example specifically demonstrates how to create a onepiece 

brushed mold without shims, which requires cutting a 

seam in the rubber to remove the master and subsequent 

castings. The master, shown in Photo 1, is made of a nonporous, 

polyurethane plastic, EasyFlo 60. As with all sealed, 

non-porous masters, they must be sprayed with a silicone 

release such as Pol-Ease ® 2300 Release Agent (when using 

polyurethane liquid rubber) and brushed with a clean, dry brush 

to insure uniform distribution of the release. Care is taken not to 

spray too much release since brush marks can be left behind and 

picked up in the finished mold. Also, excess release can be 

accidentally pushed around when brushing liquid rubber 

resulting in delamination between coats or unwanted surface 

texture. 

In order to make the mixed Poly 74-20 liquid rubber thixotropic 

so it clings to vertical surfaces, Poly Fiber II or Cab-O-Sil ® 

must be added. In this example, Cab-O-Sil is added in small 

amounts (Photo 2) and the liquid is carefully folded over to wet 

the powder (so it doesn't come out of the cup), then it is 

whipped into the rubber to a creamy, uniform consistency. Only 

a slight amount of thickening is desired in the first coat of 

rubber so all surface detail is captured without trapping bubbles 

at the mold surface. Photo 3 shows a thin, first coat of lightly 

thickened Poly 74-20/Cab-O-Sil being applied with a China 

bristle brush. After the first layer of rubber gels enough to be 

undisturbed by the next coat (~45 min - faster with Part 74 Part 

X), a second coat of slightly thicker (a little more Cab-O-Sil 

used) 74-20 is brushed over the first coat (Photo 4) and allowed 

to gel. Before Cab-O-Sil is put into the rubber to create the mix 

used for the third layer, a little unthickened Poly 74-20 is 

poured into a PlatSil ® 71-20 silicone mold to make long 1-inch 

by 1-inch strips (Photo 5) for creating a thick rubber flange that 

will be placed into the freshly gelled third coat of rubber to 

define the location of the seam line. Notice that this model has 

several "through holes" (between the arms and the legs) that 

need to be filled completely with liquid rubber to provide a 

thick enough section of rubber which will be cut when cured to 

remove the original. This third layer is done with an even more 

thixotropic, non-sag mix of 74-20 and Cab-O-Sil (Photo 6). 

When this layer is 

complete, the freshly 

gelled strip of Poly 74-20 

rubber is removed from 

the 71-20 silicone mold 

and positioned against 

the mold where the seam 

line will be cut once the 

mold cures (Photo 7). 

A final coat of lightly 

thickened rubber is 

applied after the prior 

coat gels to seal in the 

seam line strip and to 

make a smooth outer 

coating, which makes the rubber mold more attractive and fit 

better into its rigid support shell (Photo 8). Once the rubber 

mold cures (overnight, or later that day if 74 Part X accelerator 

is used), it is trimmed at the base and a clay wall is built up to a 

line that will define the parting line of the two shell sections 

(Photo 9). Since the shell will be rigid, there can be no 

undercuts that will lock it onto the rubber mold. More 

complicated models may require more shell sections to insure 

that they can be easily removed. Notice the keys/grooves in the 

clay wall that will insure proper registration of the shell halves. 

Butcher's wax is brushed over the rubber mold, allowed to dry 

for 10 minutes, then sprayed with a coat of Pol-Ease 2300 

Release Agent. 

To make the shell, Poly 1512X Polyurethane Liquid Plastic is 

mixed together (1A:1B), then Poly Fiber thickener is added to 

make it thixotropic (Photo 10). Poly Fiber is added until the 

resulting mix clings to the side of the mixing container. The 

thickened 1512X is applied ~¼-inch thick and allowed to cure 

~60 min (Photos 11). The clay wall is removed, butcher's wax 

and Pol-Ease 2300 applied to the other side of the mold and 

against the first shell section and the above procedure with 

1512X is repeated. The completed shell is drilled, bolted and 

edges sanded for easier handling (Photo 12). 

When the shell is removed, a mold key knife is used to cut a 

notch in the rubber the length of the seam from head to toe. A 

sharp scalpel is then used to cut the rest of the way to the 

master. As the rubber is peeled open, cuts are made between 

the legs and arms as needed to remove the original. Cutting in 

these areas is done using a series of short, jagged, zig-zag cuts 

in order to create a series of tiny keys that keep the seam 

registration exact (see photo above). The finished mold and 

shell are now ready for production! 

20 

(610)559-8620 • (800)858-5990


Procedures - Brush-On Mold 

Mold Making 

Methods 

Photo 1 Photo 2 Photo 3 Photo 4 




21

Mold Making 

Methods 


Procedures - Poured Blanket Mold 

Making a Two-Piece Poured Blanket Mold in a Plastic Shell 

This page details the step-by-step production of a flexible rubber 

mold and plastic mother mold of the 19-inch-tall, 19th-century 

marble statue entitled Ice Skater by Gori Nello. 

Deciding on the Type of Mold 

Openings under the arms and legs presented typical difficulties 

that influenced the selection of the type of mold to be 

constructed. The moldmaker decided on a blanket mold, poured 

in two halves into a constructed shell, because pouring yields 

better detail with less trapped surface bubbles. A poured mold 

also eliminates undercuts more easily than a brush-on mold. A 

double pour, with carefully selected parting lines, eliminates the 

need for shims (see p. 18), which would leave flashing to be 

chased, and cutting, which would be required with a single-pour 

mold and could scratch the valuable sculpture. 

Selecting the Materials 

Poly 74-30, a two-part, 1:1 mix polyurethane liquid rubber, was 

used for the mold since it is low cost, easy to mix and pour, 

flexible (Shore A30), and has good longevity. Poly 74-30 molds 

work well for casting plaster, cement, wax or resins. 

The mold shell was made with Poly 15-6, a 1:1 mix liquid 

plastic with a 5- to 7-minute working time. The plastic shell is 

lightweight and durable. [Note: Alternative materials for making 

mold shells are plaster reinforced with hemp or burlap, Polygel ® 

Plastic-75, or Poly 1512X with Poly Fiber II. The larger the 

shell, the more important it is to use lightweight shell materials.] 

Preparing the Statue 

First, the marble statue was fastened to the base with Polypoxy ® 

Quick Stick Adhesive. The base was formica-coated particle 

board from a countertop sink cut-out. To protect the marble from 

the oils of the release agent, a thin layer of PVA (polyvinyl 

alcohol) solution was brushed directly on the marble. (PVA 

solution washes off with warm water.) After the PVA dried, a 

liberal coat of release agent was sprayed over the model and 

brushed out with a dry brush to pick up any excess and to work 

release into any areas missed by the spray (Photo 1). 

Building the Mother Mold 

Next, the statue was wrapped in plastic wrap to keep it clean 

(Photo 2). Then, a ¼-inch blanket of Poly Plasticene (oil-based 

clay) was hand pressed onto the plastic wrap. To make the clay 

uniform thickness, warm Poly Plasticene (~130°F) was placed 

between 2 equal height wood strips and rolled flat using a PVC 

pipe. The height of the wood strips (¼- to ½-inch) determines 

the thickness of the clay blanket. All undercuts were filled with 

Poly Plasticene so the shell could be easily removed. 

Shims of thin aluminum flashing were placed in the clay to 

create parting lines for the shell (Photo 3). These are the only 

shims needed with the double pour process to make this mold. A 

channel was built around the edge of the clay to cause the rubber 

mold to lock into the shell. 

To build the shell for the 

first half of the mold, Poly 

Fiber was stirred into mixed 

Poly 15-6 Liquid Plastic 

until it was the consistency 

of cake frosting. Then, the 

thickened resin was laid on 

the first half of the clay in a 

manner similar to icing a 

cake. [Note: When making 

larger shells, multiple mixes 

of resin and Poly Fiber can 

be patched against each 

other to cover the entire 

surface.] After the first half 

of the shell cured (~4 hours), 

the aluminum shims were 

The original marble and plaster 

and plastic reproductions made in 

the Poly 74-30 blanket mold. 

removed and paste wax (i.e., Butcher’s Wax) and then release 

agent were applied to the first half of the shell (Photo 4). The 

second half of the shell was built against the first half in the 

same manner (Photo 5). 

Pouring the Rubber 

One-half of the plastic shell was removed along with the clay 

blanket beneath that half of the shell. Keys (tongue-and-groove 

impressions) on the second half of the clay were made in order 

for the two halves of the rubber mold to “key” or lock together 

(Photo 6). Vent holes were drilled in the shell with a ¼-inch drill 

at each high point where air would be trapped (Photo 7). The 

shell was thoroughly coated with release agent, replaced and 

positioned for pouring the rubber. Poly 74-30 was mixed and 

poured into the space within the shell where the first half of the 

clay had been. When pouring the rubber, the model was at the 

bottom of the cavity so the air bubbles would rise away from the 

model surface. As liquid rubber appeared at the vent holes, they 

were plugged with plasticene clay (Photo 8). 

After the rubber cured overnight, the shell and clay on the 

second half was removed and release agent applied to the model 

and the face of the cured rubber parting line (Photo 9). The shell 

was reassembled and rubber was poured into the shell to cover 

the model’s second half. 

After the rubber cured, the shell halves were separated by 

tapping wood wedges into the seam, gradually forcing open the 

shell to reveal the complete mold (Photos 10 and 11). 

The Casting 

Plaster was poured into the mold to clean and check the mold. 

Finally, release agent was applied, brushed out and the mold was 

properly positioned in its shell. Poly 15-3X, a mineral-filled, 

fast-setting polyurethane casting resin, was poured into the mold 

(Photo 12). The final casting was demolded in less than an hour. 

The excellent reproductions are shown with the original above. 

22 

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Procedures - Poured Blanket Mold 

Mold Making 

Methods 





23


Mold Making 

Methods 

Applications - Sculpture & Foundries 

Poly 74-30 Liquid Rubber thickened with Cab-O-Sil ® -- Sculptor Bill Hopen 

Bill Hopen, Hopen Studio in Sutton, 

WV, uses Poly 74-30 thickened 

with Cab-O-Sil ® to make a brushon 

mold of his clay “St. Joseph the 

Worker.” Three to four layers of mixed 

Poly 74-30 are applied at 60- to 90- 

minute intervals. The first layer contains 

little or no Cab-O-Sil so that air bubbles 

are minimized and fine details are 

reproduced. More Cab-O-Sil is added to 

subsequent layers for faster build up of 

the ¼- to ½-inch mold. Twenty-four 

hours after the final layer, Hopen builds a 

rigid mold shell. The great flexibility of 

rubber molds allows for easy demolding 

of delicate wax castings. The long mold 

life of Poly 74-30 has enabled Hopen 

Studio to continue producing castings 10 

years after some molds were made. These 

molds are made much more quickly than 

latex molds and at a fraction of the cost of 

silicone molds. Bill says “I’ve tried them 

all; Polytek Mold Rubber is the best.” For 

sculpture by Hopen call (304)765-5611. 

Architectural Restoration 

THR Cast Stone and GFRC of Brooklyn, NY, has restored 

many of the most architecturally significant buildings in 

New York City. Whether the medium is brownstone, 

limestone, terra-cotta, plaster, or stone, the artists, moldmakers, 

and casters at THR have reproduced and restored it to match its 

original beauty. Newly cast parts made from cast stone, glassfiber-reinforced 

concrete (GFRC), or glass-fiber-reinforced 

gypsum (GRG) appear original in every way. THR has used 

Polytek products to recreate ornamental architectural elements 

in theaters such as Lyric and Ed Sullivan, museums such as the 

Metropolitan, and hotels like the Plaza and Ansonia, as well as 

churches, schools, and private residences. THR prefers Polygel ® 

rubbers (see p. 36) for brush-on or sprayed molds that are 

created on-site from an element before it is removed from the 

building. For work back at the shop, THR often opts for Poly 

74-45. Once a mold of the original is made, a casting is taken 

and the artists meticulously recreate any eroded or missing 

detail, based on other parts of the original still in good shape, 

historical photographs, etc. Once the master is completed, a 

mold and perfect reproductions are cast. Since many 

architectural features repeat on a building, a mold such as this 

may be used again & again -- no problem for high-performance 

rubbers from Polytek. 

THR Gives New York City A Facelift with Polytek Rubbers 

The Ansonia Hotel in Manhattan is just one of the strikingly 

ornate buildings that THR has restored. Above, Philip Gallagher 

of THR displays a Poly 74-45 mold that was used to recreate 

aging architectural brackets from a 13th-floor balcony of the 

Ansonia Hotel. Cast GFRC replacement brackets in the 

background await installation. 

24 

(610)559-8620 • (800)858-5990


Applications - Home Decor 

Mold Making 

Methods 

A decorative drapery rod end was cast using EasyFlo 60 

Liquid Plastic (see p. 48), a super low viscosity polyurethane 

product, filled with bronze powder to create this faux metal 

part. The two-piece poured block mold registers nicely due to 

keys/snaps, which keep the mold aligned properly during the 

casting process. A PlatSil ® or TinSil ® silicone mold could easily 

produce many dozen resin castings or more without the need 

for release agent. 

A Poly 15-6 plastic column capital is demolded from a TinSil ® 

70-11 silicone rubber mold. This rubber is very soft (Shore 

A10) and stretchy eliminating the need for seams in the mold 

to remove cast parts. The shell was made using Poly LiteCast, 

a very low density, pourable polyurethane plastic to reduce the 

weight of the shell for easier handling. The column posthole 

was made by inserting a plastic pipe as a plug in the 70-11 

mold prior to casting. 

Props, Displays & Special Effects 

PlatSil Gel-10 was used by Gordon 

Smith of FXSmith in Toronto, 

Canada to make hundreds of 

silicone prosthetic appliances, which 

became the scales worn by 

Mystique in the blockbuster movie 

X-Men. Smith modified PlatSil Gel- 

10, a versatile 1:1 mix silicone, so 

that it was self-sticking using 

Polytek's PlatSil Deadener. This 

allowed the scales to be removed 

and reapplied for each filming 

session without adhesives. 

A PlatSil ® 71-20 silicone rubber 

mold was made from a gigantic 

fossilized shark tooth to make a 

museum display item. This twopiece 

poured block mold is 

keyed extremely well with snaps 

and a tongue-and-groove 

channel to keep the flashing to a minimum. The casting was 

made using EasyFlo 120 with 3% PolyColor Black. The liquid 

plastic was poured into one half of the mold, then the mold was 

closed and supported between two small pieces of plywood 

with rubber bands, and slush-cast by hand to produce a super 

part in 15 minutes. 

Tom Kipp of Studio 

One/Mannetron is shown 

with a hollow, rotocast 

polyester alien that was 

used as a prop in the 

movie The Roswell 

Incident. The casting 

was made in a two-piece 

brushed-on Polygel ® 40 

mold. Rotocasting 

equipment made by 

Mannetron was used to 

create several dozen alien 

figures. Polyvinyl alcohol 

was used as a barrier 

coat and the mold was 

washed in a warm 

detergent - water solution 

after several castings to 

remove styrene buildup in 

the mold, which could 

eventually damage the 

mold. This process helped prolong the mold life so that after 

several dozen castings the mold still looked like new! 


25

Mold Making 

Methods 


Applications - Concrete 

Flexible formliners of every 

size and design are routinely 

created using Poly 74, 75 

and 77-Series Polyurethane 

Liquid Rubbers. These Poly 

rubbers are tough and 

abrasion resistant making 

them ideal for the rigors of 

repeatedly casting large 

concrete parts and panels. 

These formliners can be 

made to reproduce any 

surface texture or design 

and can be bonded to 

plywood or attached to rigid 

supports for precast or castin-place 

applications. 

Cast veneer stones are made by pouring concrete into rubber 

gang molds such as this one made from Poly 74-44 polyurethane 

rubber. Individual stones can be cast simultaneously into multicavity 

molds then applied to a wall to give the look and feel of real 

stone. Flexible formliners/molds can be made of entire wall 

sections for extremely large projects. 

Poly 75 and 81 

Series Polyurethane 

Liquid Rubbers are 

used to make 

concrete stamping 

tools and texturing 

skins. These 

stamping tools are 

made by pouring 

rubber about ¾-inch 

thick onto a pattern 

that mimics the 

design that will be 

imprinted to the 

concrete. Patterns 

such as slate, brick, 

irregular flagstone or any custom design including leaves, fossils 

and much more turns otherwise boring, flat,concrete pathways, 

driveways and patios into beautifully colored and textured 

surfaces. 

Poly 74-45, a 

popular 1:1 mix, 

polyurethane liquid 

rubber, was used to 

make a paver mold. 

Pavers cast from 

molds made from 

liquid rubbers have 

much better, life-like 

surface detail than 

those made from 

rigid molds owing to 

the fact that the 

liquid rubber flows 

readily into all 

available detail on the master before curing. Hundreds to 

thousands of concrete parts can be cast from a single mold 

depending upon surface texture, proper selection of mold rubber 

and release agent, and careful demolding. 

Polygel ® Spray 35 was used to make a mold of this architectural 

element. The casting was made from glass fiber reinforced 

concrete (GFRC). The Polygel mold was created using a lowcost 

(~$4,000) machine designed to automatically meter/mix and 

spray the liquid rubber at a 1:1 ratio. The resulting mold is thin 

(~3/8-inch thick) so it is very economical and easy to peel away 

from complex shapes. Polygel rubber can be brushed for smaller 

jobs or sprayed when larger surface area molds are needed. 

This mold was sprayed in one continuous process, which took 

less than 20 minutes to complete! Polygel Spray 35 cures 

enough in 6-8 hours to allow a shell to be applied in the same 

day. 

26 

(610)559-8620 • (800)858-5990


A decorative 

concrete 

panel was 

cast as part of 

a building 

restoration 

project by 

THR Cast 

Stone and 

GFRC of 

Brooklyn, NY. 

A Poly 74-45 

mold is shown 

being 

carefully demolded. The thin poured blanket mold was supported 

by a GFRC shell and wood-framed box displayed in the 

background. 

Highway 

sound 

barriers are 

becoming 

more popular 

to keep traffic 

noise from 

residential 

areas. Poly 75 

Series 

rubbers were 

used to make 

flexible 

formliners with wildlife images to enhance the visual appeal of 

the standard ribbed wall panel design. Formliner designs 

incorporating rock, slate, brick, fossil, wood-texture and other 

architectural and artistic designs are becoming more common as 

architects realize the endless possibilities available when flexible 

molds are used. 

Polygel ® Spray 50 

was sprayed onto 

this larger-than-life 

head to make a 

thin, yet durable, 

mold. With the 

right equipment, 

this type of mold 

can be made 

anywhere -- even 

several stories 

above street level. 

Applications - Concrete 

An article in Handy 

Magazine described 

how to use Poly 75- 

80 Liquid Rubber to 

make thin, low-cost 

texturing skins to 

impart a slate 

appearance to flat 

concrete. These 

texturing skins were 

made by pouring 

Poly 75-80 over real 

pieces of slate 

(properly sealed and 

released). Once the 

first pour gelled, a 

second pour was 

made with slightly 

less rubber so it 

didn't quite flow to 

the edge of the 

previous pour. Even less rubber was used for the third pour done 

to make a texturing skin that was thicker in the middle with 

tapered edges. This allowed the thin cured rubber mats to be 

overlapped at the edges to make a seamless pattern in the 

concrete. A thin Poly 75-80 tool is shown being removed from the 

freshly textured surface. With the use of concrete colors and 

stains the results are stunning! 

A Poly Latex 60 

mold was made to 

reproduce this 

concrete angel. The 

mother mold (rigid 

shell) was made 

from Poly 15-6 

Liquid Plastic 

thickened with Poly 

Fiber to make it 

brushable. The thin 

blanket mold could 

also have been made using Polygel ® 35 or Polygel 40, highperformance 

two part brushable rubbers. Latex rubber is a onepart 

mold material, but 15-30 coats of rubber applied over 

several days are required to complete the mold. A Polygel mold 

can be made in a matter of hours! This Angel blanket mold is a 

one-piece glove mold with no seams, whereas the rigid shell is 

made in several sections to accommodate numerous undercuts. 

If you can pour concrete, 

you can pour liquid rubber! 

Mold Making 

Methods 


27

Mold Making 

Methods 


Applications - Prototyping & Model Making 

Prototype Parts of All Kinds Made with Polytek Liquid Rubbers & Plastics 

Larami Limited, headquartered in Mt. Laurel, 

NJ, is the originator and manufacturer of the 

internationally-recognized Super Soaker ® toy 

water guns. With engineering and prototype 

model development facilities in Whitehouse 

Station, NJ, Larami Limited has been using 

Polytek’s mold rubbers, such as PlatSil ® RTV 

Silicones, and casting plastics, such as Poly 

15-3X, Poly 1512 and Poly-Optic ® 1410, very 

successfully to create their new products. 

Producing the Prototype 

Many different techniques involving numerous 

Polytek products are employed in the 

production of a unique model or prototype part 

such as the Super Soaker. Master models can 

be carved from wood, sculpted from clay, 

machined from polyurethane board, wood or 

plaster using CNC equipment, or created from 

a liquid photopolymer using a stereolithography 

process. 

As with any mold making process, it is 

important to determine the most appropriate 

combination of mold making and casting 

materials for the project at hand. If wax 

castings are to be made (say for a lost wax 

process as is used for making many metal 

prototype parts), then a polyurethane mold 

rubber such as Poly 74-30 or Poly 74-45 (see 

p. 34) may be the best choice as they are most 

PlatSil ® 71 and 73 Series mold rubbers 

are widely used for model making and 

prototyping. This two-piece block mold 

made of PlatSil 71-35 is used to reproduce 

a thin-walled car model. Prototypers cast 

dimensionally accurate parts fast using 

EasyFlo 60 Liquid Plastic (see p. 48). 

cost-effective and release waxes nicely. 

Many times plastic parts are the desired end 

result, as in the case of a Super Soaker. 

PlatSil ® and TinSil ® RTV Silicone Rubbers 

(see pp. 40-45) are the best choice for casting 

polyurethane plastic prototypes. These highperformance 

silicone rubbers offer the best 

mold life and resistance to damage from 

repeated casting with chemically aggressive 

liquid polyurethane resins. TinSil 70-25 and 

70-39 are popular silicone rubbers for 

modelmakers since they are lower-cost, tincatalyzed 

systems and have hardnesses that 

makes difficult parts easy to demold. When 

using any tin-catalyzed silicone rubber, be sure 

to perform a test cure to insure the alcohol 

released during the rubber’s cure does not 

interfere with the cure of the polyurethane 

plastic. If alcohol on the mold surface poses a 

problem, heating the mold to 200°F for several 

hours can assist alcohol removal. 

Any PlatSil rubbers can be used for casting 

polyurethane plastics. PlatSil 71-20 is an easy 

1:1 mix, Shore A20 rubber with a super low 

viscosity and 4-hour demold. For applications 

requiring firmer rubber, PlatSil 71-35, 73-45, 

or 73-60 provide excellent tear and suitable 

hardnesses. When pouring any one of the 

TinSil or PlatSil rubbers over a model, Pol- 

Ease ® 2350 Release Agent (non-silicone) 

should be evaluated as a release. 

Poly Plastics Have Thermoplastic Feel 

The Poly 15-Series products (see p. 49) offer 

many types and speeds of cure for almost 

every application. Poly 1512 and 1512X are 

most popular for prototypers interested in a 

tough, high-performance product with a 

thermoplastic feel. It has a 1:1 mix, can be 

easily colored with PolyColors, has low 

viscosity, a fast (5 min) or slow (20 min) 

potlife, and very impressive physical 

properties when cured. It is non-brittle in thin 

sections and has a high tensile strength. It can 

be sanded, carved, machined or painted as 

needed. Other 15-Series plastics can be used 

for lower (Poly LiteCast , page 54) or higher 

density (Poly 15-3X) parts. Poly 15-8 is also 

available for modelmakers interested in 

making heat-resistant tools for vacuumforming 

applications. For rapid-casting 

applications of complex parts requiring a resin 

Larami Ltd., originator of the Super 

Soaker ® , uses Polytek’s rubber and plastic 

products to make molds and castings for 

various prototyping projects. 

with a super-low mixed viscosity, try 

EasyFlo 60 Liquid Plastic (see p. 48). 

Rotational Casting 

An additional use of Polytek fast casting 

plastics at Larami was to rotationally cast the 

large pressure tank prototype for the Super 

Soaker squirt gun by rotating the hollow tank 

mold with a small amount of a Poly Plastic 

such as Poly 15-3X coating all surfaces as it 

set. Poly 15-3X sets in about 15 minutes at 

room temperature, but the silicone rubber 

mold was heated to hasten the set and 

demolding time of the Poly 15-3X resin. All 

Poly 15 Series resins can also be accelerated 

with a few drops of Poly 15 Part X 

Accelerator. See pages 46-56 for more 

information on Polytek’s Liquid Plastics and 

page 64 for more on rotocasting. 

Water-Clear Poly-Optic ® 1410 

Another Polytek polyurethane plastic used by 

Larami is Poly-Optic 1410, a water-clear, low 

viscosity resin, which can be used for 

transparent parts such as face shields, toy-auto 

windshields, windows, headlights and eyes. 

Pressure casting can help 

prototypes and model 

makers create perfect, 

bubble-free castings. 

See page 16. 

28 

(610)559-8620 • (800)858-5990


Brush-On Polygel ® Molds Used to Cast Polyester/Fiberglass Capitals 

Russ Veder, of American Architectural Art, chose Polygel rubbers because 

of their ability to be brushed on easily and capture incredible detail. Edon 

moldmakers Matt Axel and Bob Mathias agreed, "Polygel was the best mold 

rubber we ever used. After casting 10 large fiberglass parts, the mold was 

in such good condition, we could have made 50 more." 

Applications - Cast Polyester/Fiberglass Parts 

Restoration of the Widener Building in Philadelphia 

began in the summer of 1990, by Russ Veder, an 

expert in architectural restoration and principal of 

American Architectural Art. This project required 

making detailed flexible rubber molds of the 

building's ornate Corinthian column capitals, which 

measure 8 feet by 7 feet with deep 24-inch undercuts. 

Russ, with subcontractor, Edon Corp., resculpted a 

fiberglass duplicate of the aged capital to bring it 

back to its original design. The duplicate was used as 

a working model to make a Polygel mold that 

ultimately produced the 10 fiberglass capitals needed 

for the restoration. Fabric reinforcement was pressed 

into the wet rubber where needed and soft, flexible 

foam was pressed into the undercuts to allow the 

shell to be removed more easily. A final coat of 

Polygel 40 was used to cover the fabric and foam. A 

fiberglass shell was made the following day. Cast 

fiberglass/ polyester resin parts were sprayed into the 

Polygel mold that was coated with a polyvinyl 

alcohol (PVA) barrier coat to protect the mold from 

the harsh effects of the polyester resin. 

Mold Making 

Methods 

Poly Latex for Polyester Fiberglass Parts -- Capitol Displays 

Poly Latex 60 was brushed on a sculpted resin model to produce this large 

blanket mold for a decorative architectural part. 

Tony Lorino, Capitol Displays of Nashville, TN, 

uses Poly Latex 60 molds to produce polyester and 

fiberglass copies of original sculpted models. Poly 

Latex 60 is the rubber of choice because of it’s 

durability and ease of application. Being a single 

component material, Poly Latex 60 is brushed on 

without the limitation of a pot life. Ten to twenty 

coats are applied, two per day, to build up proper 

mold thickness. Gauze is often incorporated into the 

latex to lend additional strength to large molds. 

Lorino then builds a rigid polyester and fiberglass 

mold shell over the latex mold to maintain the shape 

of the mold during casting. Poly 15-6 and Poly 

Fiber, or Polygel ® Plastic-75 should also be 

considered for this application. The end result is a 

lightweight, high tear strength mold with good 

resistance to the swelling caused by polyester resin. 

Poly Latex 60 molds allow Capitol Displays to 

produce detailed parts with undercuts that would be 

impossible with rigid molds. 


29

Mold Making 

Methods 


Applications - Foam Parts & Shells 

Poly 15-3X, 1:1 mix 

polyurethane plastic, was 

rotocast to create a thin, 

lightweight, hollow casting. 

After the 15-3X gelled in ~5 

minutes, Poly 15-6 

polyurethane plastic with 3% 

(by weight) Part 15F Foamer 

was poured into the hollow 

15-3X shell while still in the mold. The 15-6/Part F open-cell 

foam expanded to fill the cavity giving the hollow casting support 

without adding much cost or weight. 

PolyFoam R-5, a 1:1 by 

volume rigid foam, was used 

to create a very lightweight 

mold shell to support this 

brushed blanket mold of Poly 

74-29 polyurethane rubber. 

The shell was made by 

pouring liquid PolyFoam R-5 

into an unsealed wooden box built around the cured rubber mold 

that was covered with butcher's wax for release. When the foam 

expanded, it adhered to the box and conformed to the shape of 

the rubber mold. A little foam goes a long way! 

Hollow Lightweight Castings 

PolyFoam R-8, a 1:1 by 

volume, closed-cell foam, 

makes strong, lightweight 

castings quickly. PolyFoam is 

mixed and poured into a 

TinSil ® or PlatSil ® silicone 

rubber mold, which is covered 

with a lid to pack the foam to a 

higher density for good mold 

fill, thicker skin, and better 

surface detail. About 20 

minutes later, parts such as 

this plaque or pot can be 

removed from the mold. A barrier coat, such as Barrier PF, can 

be applied to the mold to prolong mold life and provide 

primed/painted parts upon demold. 

PolyFoam R-5 and R-8 

can be used to easily 

create parts such as 

these plaques. Since 

the foams are selfskinning, 

the plaques 

have all the detail of the 

original. 

Poly 1512X, a 1:1 mix, 

pourable, high strength, 

polyurethane liquid plastic 

was mixed with PolyFiber 

thickener to turn the 

pourable plastic into a 

non-sag, thixotropic mix 

that was laid up by hand 

into a Polygel ® mold of a boulder. A thin face coat followed by a 

thicker backup coat were applied to create a total thickness of 

approximately ¼ inch. Very little material was needed, so the 

resulting casting was lightweight and low cost. A similar hollow 

casting could have been made using polyester resin and 

fiberglass or glass-fiber reinforced concrete. 

This 10-inch tall head was rotocast using 

just a few pounds of EasyFlo 120, a 1:1 

by volume mix, polyurethane plastic that 

is designed for rotocasting (see 

equipment on p. 63) and slush casting, 

which is done by hand. If poured solid, 

this casting would weigh and cost much, 

much more. EasyFlo 120 captures all 

the detail without thin spots or bubbles. 

A poured blanket mold made of Poly 74-20 polyurethane rubber 

was made from a chainsaw-carved wooden bear to create 

lightweight duplicates. Notice the thickened seam line in the 

back of the mold that was cut with a mold key knife to permit 

easy demolding and minimal seam cleanup. Since this mold is 

larger, "snaps" or "buttons" were made in the clay blanket which 

ultimately became part of the rubber mold so the mold would not 

flop away from the shell while being rotated in the rotocasting 

machine. 

30 

(610)559-8620 • (800)858-5990

This 12-inch tall 

sculpture of a 

mother and child 

was created by Mary 

Smith of Leesport, 

PA, and was molded 

at a Polytek Seminar 

& Workshop using 

PlatSil ® 71-10 Liquid 

Silicone Rubber. The 

sculpture was 

disassembled into 

two pieces so that 

the child could be 

molded separately 

from the mother. The 

cold-cast bronze 

figurines were made 

by slushing a thin coating of Poly 1512X mixed with bronze 

powder around the surface of the mold until it gelled. Then a 

dense, low-cost polyurethane plastic (Poly 15-3X) was used as a 

backfill to simulate the weight of a real bronze casting. The 

resulting figurines were glued together using EpoxyBond 

adhesive and felt was applied to the bottom. Faux bronze at its 

best! 


Applications - Statuary & Figurines 

These frogs were cast in a 

TinSil ® 70-25 silicone mold. 

Each cold cast bronze was 

made from EasyFlo 60 

Plastic with bronze (mix ratio 

1A:1B:2 bronze, by volume) 

and finished with a different 

patina for a unique look. 

A poured blanket mold was made using PlatSil ® 71-20 Liquid 

Silicone Rubber, a unique, 1:1 mix, 4-hour-cure system, which 

can be used to cast any medium. This gargoyle could now be 

cast in plaster, 

concrete or any 

pourable plastic 

using this PlatSil 

mold. This blanket 

mold was poured in 

a single piece, then 

cut, using a mold 

key knife, up both 

sides to create a 

mold which opens 

like a book. 

Mold Making 

Methods 

The use of Polytek’s liquid mold rubbers 

and casting plastics is not just limited to 

the applications described on the past 

several pages! 

• Candle makers 

• Soap manufacturers 

• Jewelers 

• Taxidermists 

• Forensic scientists 

• Hobbyists of all kinds 

• Inventors 

• & many others 

Use Polytek products to make their 

creations. 

& More! 

If you have an application you don’t see 

here, call Polytek Customer Service for 

assistance. 

The use of Polytek materials is limited 

only by the imagination -- may yours be 

limitless. 


31

2 Polyurethane RTV Mold Rubbers 

Polyurethane RTV Liquid Mold Rubbers 

Polyurethane 

Mold Rubber 

Polytek offers several Polyurethane RTV Liquid Mold Rubbers 

each formulated to meet various customer applications. Polytek’s 

polyurethane mold rubbers consist of a Part A and a Part B that, 

after mixing, cure at room temperature to flexible, high-strength, 

mold rubbers. Polyurethane rubbers make durable, easy releasing 

molds for casting plasters and waxes without release agents, but 

when used with proper release agents are also excellent for casting 

concrete, epoxy, polyester, urethane and acrylic. 

For many Polytek polyurethane mold rubbers, the last two digits 

in the product name indicate the approximate Shore A hardness 

of the cured rubber. Polytek polyurethane mold rubbers range in 

hardness from a very soft A20 to a very firm D45. 


Porous models, such as wood, plaster, stone, pottery or masonry, 

must be sealed, then coated with a release agent. Multiple coats 

of paste wax dried and buffed will seal most surfaces. Potters 

soap can be used as a sealer for plaster. Lacquer, paint, PVA, 

PolyCoat and Pol-Ease ® 2350 also work well as sealers for many 

surfaces. Models made of sulfur-containing modeling clay (i.e., 

Roma Plastilina) should be sealed with shellac. [CAUTION: 

When shellac is used as the sealer, it must be thoroughly coated 

with release agent because polyurethane rubbers bond tenaciously 

to shellac. In fact, uncoated shellac may be used to bond 

polyurethanes to certain surfaces (i.e., plaster).] 

Non-porous models (i.e., metals, plasticene, wax, glazed ceramics, 

fiberglass, and polyurethanes) and sealed porous models 

should be coated with a release agent such as Pol-Ease 2300. 

If there is any question about the compatibility between the liquid 

mold rubber and the prepared model surface, perform a test 

cure on an identical surface to determine that complete curing and 

good release is obtained. 

Porous models must be vented from beneath to prevent trapped 

air from forming bubbles in the rubber (see p. 12). 

POLYURETHANE MOLD RUBBERS: 

AT A GLANCE 

Poly 74 & 75 Series - Flexible, high-strength mold rubbers 

for making tough, durable molds. Polytek’s easiestto-use 

and best-selling mold rubbers! 

Polygel ® Series - Thicken immediately upon mixing 

components making these products exceptional for 

making brush-on or sprayed blanket molds. 

Poly 77 Series - High elongation mold rubber for maximum 

mold life in high volume applications. 

Poly 81 Series - Firm rubber for making durable molds, 

forms or industrial parts. 

Poly 72-40 Series- Flexible rubber that performs well 

for casting wax and plaster. 

Poly GlassRub- Clear, flexible rubber for making cut 

molds or casting clear or colored art/decor objects. 

MIXING AND CURING 

Before mixing rubber, be sure that both Parts A and B are at room 

temperature and that all tools and models are ready to go! Check 

product labels or technical bulletins to determine working time 

for the product -- some products set fast -- meaning that you must 

work quickly. 

Many Polyurethane Part Bs require stirring before use. If there is 

a “Stir Before Use” label on the container -- be sure to do so. 

Mix Ratios Vary! Check the mix ratios for the specific product 

you are using. For polyurethane rubbers, most mix ratios are 

expressed by weight. Carefully weigh Parts A and B in proper 

ratio. [Note: Polygel products can be mixed 1:1 by weight or volume. 

See p. 36.] 

Weigh Part B (usually the lower viscosity component) into a 

clean metal or plastic mixing container. Then weigh the appropriate 

amount of Part A into the same container. Mix thoroughly. 

Hand mixing with a Poly Paddle (see p. 62) is best to avoid mixing 

air into the rubber. While mixing, scrape the sides and bottom 

several times to insure thorough mixing. Pour the rubber as soon 

after mixing as possible for best flow and air bubble release. 

Vacuum degassing or pressure curing helps to provide bubble 

free molds, but is usually not necessary. 

Allow the rubber to cure at room temperature, 77°F (25°C). Heat 

accelerates the cure - low temperatures slow the cure. Avoid curing 

in areas where the temperature is below 60°F (15°C). 

Check product labels or technical bulletins to determine appropriate 

cure times. For most polyurethane products, final cure 

properties are obtained in about seven days, but most molds may 

be used with care after curing for 24 to 48 hours. 


Usually no release agent is necessary when casting plaster or 

molten wax in polyurethane molds. When casting with plaster, 

sponge, dip, or spray the mold with Pol-Ease Mold Rinse and then 

pour plaster on the wet mold to reduce air bubbles in the plaster 

and aid release. When casting resin, spray the mold with Pol-Ease 

2300 Release Agent. For casting concrete, use an appropriate 

form release such as Pol-Ease 2650 or 2601 Release Agent. 

Exposure to solvent-containing form releases should be kept to a 

minimum to reduce likelihood of mold distortion due to shrinkage 

or swelling. 

After repeated casting with certain resins, plaster and concrete, 

molds may shrink or swell since these materials can either extract 

oils from the mold or force chemicals into the rubber matrix. The 

proper selection of release agent and/or barrier coat can minimize 

this effect. If shrinkage becomes evident, a light application of 

32 

(610)559-8620 • (800)858-5990

Polyurethane RTV Mold Rubbers 2 

Pol-Ease Mold Dressing can help to restore the mold to its original 

dimensions. For more information on the use of Pol-Ease 

Mold Dressing, call Polytek Customer Service. 

ADDITIVES 

Polytek offers various additives that can be used to vary the properties 

of the cured and uncured polyurethanes. 

• Softener - For the Poly 74, 75 and 77 Series RTV Liquid 

Mold Rubbers, add Poly 74/75 Part C Softener for a lower 

viscosity mix and a softer cured rubber. Poly 74/75 Part C 

Softener may be added to most other Polytek polyurethane 

mold rubbers except Poly 72-40. 

• Accelerator - For Poly 74, 75 and 77 Series RTV Liquid 

Mold Rubbers, Poly 74/75 Part X can be added to accelerate 

the cure. Poly 74/75 Part X may accelerate other Polytek 

polyurethane mold rubbers. Test on a small scale first. 

• Thickeners - Poly Fiber II is a fine fiber that is used to thicken 

polyurethane rubbers and plastics to a thixotropic consistency 

for brushed rubber molds and plastic shells. Cab-O- 

Sil ® Fumed Silica is both a thickener and thixotropic agent. 

Add Poly Fiber II or Cab-O-Sil to mixed Parts A and B in 

order to form a gel appropriate for application by brush or 

trowel. Cab-O-Sil is only appropriate for use with certain liquid 

mold rubber products. 

• UV Stabilizer - Poly UV Additive can be added to mixed 

Parts A and B to improve UV resistance of cured Polytek 

mold rubbers. At 0.5% of the total weight of the liquid mix, 

UV Additive reduces characteristic surface degradation 

caused by sunlight and other UV sources. 

• Colors - Polyurethanes can be tinted to various colors by 

adding small amounts of PolyColors (see p. 61). 

To learn more about additives, refer to product technical bulletins 

or call Polytek Customer Service. Additives and accessories for 

polyurethane mold rubbers are listed in the box to the right. 

CLEAN UP 

Tools should be wiped clean before the rubber cures. Denatured 

ethanol is a good cleaning solvent, but it must be handled with 

extreme caution owing to its flammability and health hazards. 

Work surfaces can be waxed or coated with Pol-Ease 2300 

Release Agent so cured rubber can be removed. 

SAFETY 

Before use, read product labels and Material Safety Data Sheets. 

Follow safety precautions and directions. Contact with uncured 

products may cause eye, skin and/or respiratory irritation and dermal 

and/or respiratory sensitization. Avoid contact with skin and 

eyes. If skin contact occurs, remove with waterless hand cleaner 

or alcohol then soap and water. In case of eye contact, flush with 

water for 15 minutes and call a physician. Use only with adequate 

ventilation. Do not use polyurethane products where food or body 

contact may occur. Polyurethanes burn readily when ignited. 

STORAGE LIFE 

At least six months in unopened containers stored at room temperature 

(60-90°F). Parts A and B react with atmospheric moisture 


Molds and castings made from Polytek polyurethane products. 

ADDITIVES & ACCESSORIES 

Poly 74 Part C Softener 

1 pint (1 lb), 1 gal (8 lb), 5 gal (40 lb) 

Poly 74/75 Part X Accelerator 

1 pint (1 lb), 1 gal (8 lb) 

Pol-Ease ® 2300 Release Agent 

12-oz. can, case of 12 cans 


1 qt (2 lb), 5 gal (40 lb) 


12-oz. can, case of 12 cans 


1 qt (2 lb), 5 gal (40 lb), Drum (450 lb) 


1 qt (1.5 lb), 5 gal (35 lb), Drum (375 lb) 

Pol-Ease ® Mold Rinse or Mold Dressing 

5 gal (40 lb) 

Poly PVA Solution (Green or Clear) 

1 qt (2 lb), 5 gal (40 lb) 

PolyCoat 

1 qt (1.5 lb), 1 gal 

Poly Purge Aerosol Dry Gas 

10-oz can, Case of 12 cans 

Cab-O-Sil ® /Fumed Silica 

5 gal, 1 bag (10 lb) 

Poly Fiber II 

5-gal pail (~3 lb), bag (10 lb) 

and, therefore, should be used up as soon as possible after opening. 

After opening, spray Poly Purge Dry Gas Blanket into containers 

before resealing to displace moist air and extend storage life. 

Polyurethane rubber molds can last many years if stored in their 

proper shape in a cool, dry location out of direct sunlight. 

Polyurethane 

Mold Rubber 

33


Poly 74 and 75 Series RTV Liquid Rubbers 

Polyurethane 

Mold Rubber 

DESCRIPTION: Poly 74 and 75 Series Liquid Rubbers consist 

of Part A and Part B that, after mixing, cure overnight at room 

temperature to flexible, high-strength, mold rubbers. Poly 74 and 

75 Series Rubbers make durable, easy releasing molds for casting 

plasters and waxes without release agents, but when used with 

proper release agents are also excellent for casting concrete, 

epoxy, polyester, urethane and acrylic. 

MODEL PREPARATION: See p. 32. 

MIXING AND CURING: See p. 32. 

USING THE MOLD: See p. 32. 

ADDITIVES: For general guidelines see p. 33. 

Softener - For the Poly 74 and 75 Series RTV Liquid Mold 

Rubbers, Poly 74/75 Part C Softener can be added to the uncured 

products for a lower viscosity mix and a softer cured rubber. 

When Part C is used, cure time is longer and there is some loss of 

strength in the rubber and increased tendency to shrink after 

repeated castings. To soften Poly 74-30 to a Shore A15, mix 

1A:1B:1C, by weight. The quantity of Part C required to soften 

other products varies and should be determined through experimentation. 

Accelerator - For the Poly 74 and 75 Series RTV Liquid Mold 

Rubbers, Poly 74/75 Part X can be added to accelerate the cure. 

Part X is most useful when making brush-on molds with 74- 

Series rubbers to decrease the time needed between coats. By 

adding 3% Part X (by weight of the total mix) to 74-30 or 74-29, 

FEATURES 

• Easy-to-use formulations 

• Flexible, strong mold rubbers 

• Reproduce fine details 

• Make tough, long-lasting molds and parts 

the working time is reduced to approximately 8 minutes -- in the 

time it takes to mix the next batch, the previous brushed layer 

gels enough to apply the next coat. Demolding is possible in as 

little as 4 hours after the final layer is applied. Rapid curing with 

Part X allows a firm, yet flexible shell or mother mold to be made 

in the same day. For example, by adding 1% Part X (by weight 

of total mix) to Poly 75-80, the working time is reduced to 

approximately 10 minutes and demolding is possible in as little 

as 6 hours. 

Exercise caution when using Part X for poured molds since the 

rapid onset of gelling may trap air bubbles on or near the surface 

of the master. 

Poly 74/75 Part X affects each product differently. Before use, 

testing to determine the best amount of Part X to use is advised. 

CLEAN UP: See p. 33. 

SAFETY: See p. 33. 

POLY 74 SERIES PHYSICAL PROPERTIES 

74-20 74-29 74-30 74-40 74-44 74-45 74-55 

(74-29 White) (74-30 Clear) 

Mix Ratio, By Weight 1A:2B 1A:1B 1A:1B 2A:1B 2A:1B 1A:1B 4A:1B 

Hardness, Shore A 20 30 30 40 45 45 55 

Pour Time (min) 30 30 30 20 20 30 15 

Cured Color* Yellow Black Varies Varies Gray Yellow Clr Yellow 

(White) (Clear/Amber) 

Mixed Viscosity (cP) 800 2,800 2,000 3,400 3,500 2,500 4,000 

Specific Volume (in 3 /lb) 27.5 27.5 27.5 27.5 27.5 27.5 27.5 

POLY 75 SERIES PHYSICAL PROPERTIES 

75-59 75-60 75-65 75-70 75-75 75-79 75-80 75-90 

Mix Ratio, By Weight 1A:1B 1A:1B 1A:1B 1A:1B 2A:1B 2A:1B 2A:1B 2A:1B 

Hardness, Shore A 60 60 65 70 75 80 80 90 

Pour Time (min) 10 10 35 40 20 20 45 10-15 

Cured Color Amber Amber Yellow/Amber Gray Amber Yellow Yellow/Amber Tan/Brown 

Mixed Viscosity (cP) 2,500 1,200 3,000 3000 4,000 2,000 5,000 6,000 

Specific Volume, in 3 /lb 27 27 27 27 26 26 26 26 

* Some Part Bs darken with age, but cured rubber properties are not affected. 

34 

(610)559-8620 • (800)858-5990


Moldmaker Chan 

Oeur (looking at 

camera) demolds a 

Poly 74-30 brushed 

mold from one of six 

panels created by 

artist Kate Burke for 

the Minnesota 

Veteran’s Home. 

They sprayed the 

model with Pol-Ease ® 

2300 Release Agent, 

so the separation 

was perfectly clean 

and trouble-free. 

Poly 74-20 offers the most 

remarkable combination of 

tear strength and softness. 

With tear strength similar to 

harder rubbers, Poly 74-20 

pulls away from detail and 

undercuts with no trouble at 

all. Poly 74-20 is great for 

casting concrete, plaster 

wax and resins. 

A satisfied seminar 

attendee displays her 

cold cast bronze pot 

demolded from a twopiece, 

poured block mold 

made from Poly 74-20. 

The keys, which register 

the top and bottom 

halves of the mold, 

worked perfectly to create 

a thin, uniform wall 

thickness on the cast 

part. 

Poly 74-40 was used to make 

a poured blanket mold of this 

shelf bracket. The bracket was 

rotocast using Poly 15-3X 

polyurethane to make a hollow 

part that was then backfilled 

with Poly 15-6 and Part 15F 

Foamer to give it strength 

while keeping it lightweight 

and low cost. 

Polyurethane 

Mold Rubber 

74- & 75-Series Packaging 

Product 

(Mix Ratio) 

Unit Weight 

(lb) 

Unit Components 

Part A (lb) Part B (lb) Part A (volume) Part B (volume) 

Poly 74-20 

Mix Ratio: 1A:2B 

6 

24 

120 

1,350 

2.0 

8.0 

40.0 

450 

4.0 

16.0 

80.0 

900 

1 qt 

1 gal 

5 gal 

55 gal 

2 x 1 qt 

2 x 1 gal 

2 x 5 gal 

22 x 5 gal/2 x 55 gal 

Poly 74-29, 74-30, 74-30 Clear, 74-45 

Poly 75-59, 75-60, 75-70 


4 

16 

80 

900 

2.0 

8.0 

40.0 

450 

2.0 

8.0 

40.0 

450 

1 qt 

1 gal 

5 gal 

55 gal 

1 qt 

1 gal 

5 gal 

55 gal/11 x 5 gal 

Poly 74-40, 74-44 

Poly 75-75, 75-79, 75-80, 75-90 


6 

24 

120 

675 

1,350 

4.0 

16.0 

80.0 

450 

900 

2.0 

8.0 

40.0 

225 

450 

2 x 1 qt 

2 x 1 gal 

2 x 5 gal 

55 gal 

2 x 55 gal 

1 qt 

1 gal 

5 gal 

6 x 5 gal 

55 gal 

Poly 74-55 


5 

20 

40 

100 

562.5 

4.0 

16.0 

32.0 

80.0 

450 

1.0 

4.0 

8.0 

20.0 

112.5 

2 x 1 qt 

2 x 1 gal 

5 gal 

2 x 5 gal 

55 gal 

1 pt 

2 x 1 qt 

1 gal 

5 gal 

3 x 5 gal 


35


Polygel ® 

Brushable/Sprayable Mold Rubber 

U.S. Patent # 5,128,433 

Polyurethane 

Mold Rubber 

USES: Polygel ® Mold Rubbers are without equal for brushed or 

sprayed blanket molds. Polygel Plastics produce strong, lightweight 

mold shells (see p. 46). Polygel products are ideal for 

molds and shells built up with a brush or spatula on vertical or 

overhead surfaces. Evaluate Polygel Mold Rubbers for casting 

plaster, cement and waxes, as well as for limited casting with 

polyester, epoxy and polyurethane resins. Sprayable Polygel 

products are ideal for large surface area applications where brushing 

may be impractical. Polygel products bond well to many surfaces 

and should be evaluated as adhesives and sealants. 

DESCRIPTION: Polygel products consist of liquid Parts A and 

B, that after mixing 1:1 by weight or volume, immediately selfthicken 

to a brushable or trowellable consistency. As the liquid 

components of Polygel Mold Rubbers are mixed together, the 

product changes color and thickens to a buttery, non-sag paste 

with a working time of 1 to 20 minutes (depending on the specific 

Polygel product used). A mold can be built up in 2 to 3 coats, 

applied about 1 hour apart. Polygel Spray 35, Spray 50 and Quick 

Spray 50 can be sprayed continuously until the desired mold 

thickness is achieved. Polygel rubbers cure overnight at room 

temperature to flexible, tough rubbers. Polygel Spray 35 and 

Quick Spray 50 cure in 4-6 hours. 



FEATURES 

• Easy -- 1:1 mix by weight or volume 

• Excellent for brush-on and spray applications 

• Fast -- one-day molds 

• Tough and strong 

• Color-coded mix indication 

• Molds have long library life 

• Good flow into fine detail 

• Good dimensional stability 

BRUSH-ON MOLDS WITH POLYGEL RUBBER: When 

brushing Polygel rubber, allow the first coat to gel enough so that 

the second coat will not disturb it (usually about 1 hour is adequate, 

30 minutes for Polygel 35), then apply a second coat being 

careful to cover any thin spots in the first coat. Do not allow prior 

layers to cure completely before applying subsequent coats. 

Sprayed molds should be made in one continuous application 

without the need for individual layers. Ideally, a blanket mold 

should be at least 1/8-inch thick but not more than 3/8-inch, since 

too thick a layer of rubber causes difficulty turning a mold back 

on itself during demolding. Allow to cure at room temperature 

prior to demolding or building the mold shell. Strength continues 

to develop for several days. 

36 

Polygel Product Options 

Polygel ® 35 - Softest, most elastic, brushable Polygel rubber. 

Cures to Shore A35 hardness in 4-6 hours. 

Polygel ® Spray 35 - Sprayable version of Polygel 35 

designed for use with meter-mix spray equipment. 

Polygel ® 40 - The lowest viscosity mix for best air bubble 

release and easiest brushing. Cures to a Shore A40 hardness. 

Polygel ® 50 - A thicker mix that cures to a tough Shore A50 

hardness. Polygel 50 is a great adhesive for repairing 

polyurethane molds and bonding molds to backing material 

such as plywood. 

Polygel ® Spray 50 - Designed for spray mold applications 

using meter-mix spray equipment. 

Polygel ® Quick Spray 50 - A fast, sprayable mold rubber 

with a 1-minute working time and a 4 to 6-hour cure. 

Polygel ® Plastic-75 - See p. 55. 

Polygel ® Shell - See p. 55. 

REINFORCING BRUSH-ON MOLDS: Rubber molds can be 

reinforced with Tietex ® Fabric (see Accessories), which is strong 

and wets out better than other fabrics. Tietex can be laminated at 

the top of a seam or strips can be laid around the perimeter of a 

mold to prevent tearing. The fabric can be embedded in the second 

or third coat of rubber while tacky and covered with a subsequent 

coat, which should be as fluid as possible for best penetra- 

Polygel ® Mold Rubbers are specifically designed for brush-on 

and spray application. After Parts A+B are mixed, they form a 

thixotropic gel that clings to vertical and overhang surfaces after 

application. 

(610)559-8620 • (800)858-5990


Polygel ® Spray 50 is 

applied to a monumental 

sculpture with 

the VS-3000 Polygel 

Sprayer (see p. 64). 

Using the sprayer, the 

entire mold was made 

in a continuous 

sprayed piece. The 

gel emitting from the 

sprayer is non-sag 

and, therefore, stays 

where it is applied, 

but can be moved 

around with a brush if 

necessary. 

tion of the cloth. If the fabric is too close to the model surface, the 

weave pattern may show through to the face of the mold. 

NOTE ON LAYERING DIFFERENT POLYGEL RUBBERS: 

Typically, brush-on molds should be completed with one rubber. 

For example, if the face coat is brushed with Polygel 40, then all 

subsequent coats should be with Polygel 40. In some cases, the 

initial coat can be brushed with lower viscosity Polygel 35 or 40 

for better detail and the second (usually final) coat with thicker 

Polygel 50 to speed the mold making process. This technique is 

acceptable for molds that do not require long-term storage or use. 

When layering different products, oils can transfer from one rubber 

to another causing warping or curling of the mold. In extreme 

cases, a mold can distort enough that it will not fit properly into 

its shell. 

THICKER MIXES FOR FILLING UNDERCUTS: Polygel 

Mold Rubbers can be made even thicker by stirring Poly Fiber II 

or Cab-O-Sil ® into the mixed Parts A and B. 

USING THE MOLD: See p. 32. If a Polygel rubber mold is to 

be turned inside out like a sock, the outside surface must be lubricated 

with soapy water or petroleum jelly so that it slides over 

itself easily. The shell or mother mold can be made of Polygel 

Plastics, plaster, polyester resin and fiberglass, or Poly 15-6 or 

1512X resin filled with Poly Fiber or fiberglass (see p. 61). If the 

shell is built with Polygel Plastics or other resin, the rubber must 

be thoroughly coated with paste wax then Pol-Ease 2300 Release 

Agent to prevent the plastic from sticking to the rubber. A plaster 

shell must be sealed with potter’s soap, shellac, lacquer or wax to 

prevent mold distortion during storage or use. 


SAFETY: See p. 33. When spraying Polygel products, use adequate 

ventilation and personal protective equipment (i.e., respirators, 

gloves, coveralls). 


Products 

Polygel 35 

Polygel 40 

Polygel 50 

POLYGEL MOLD RUBBER PACKAGING 

Polygel Spray 35 

Polygel Spray 50 

Polygel Quick Spray 50 

A large, flexible 

rubber dome 

mold was made 

quickly using 

Polygel ® Spray 

50 for the 

restoration of 

the St. Joseph 

County 

Courthouse in 

Southbend, IN. 

Using Polygel ® 

Spray 50 a mold 

was made of 

this this large 

cornice bracket. 

This Polygel ® 

mold was used 

to rotocast hollow 

plaster 

columns used 

routinely for 

home and office 

decor. 

Unit Weight (A+B) 

4 lb 

16 lb 

80 lb 

900 lb 

80 lb 

900 lb 

Polyurethane 

Mold Rubber 

37


Poly 77 Series RTV Liquid Rubbers 

Polyurethane 

Mold Rubber 

DESCRIPTION: Poly 77 Series RTV Liquid Rubbers consist of 

a liquid Part A and Part B that, after mixing, cure at room temperature 

to economical, flexible mold rubbers. Consider these 

products for casting plasters, cements and waxes. Resins can also 

be cast with proper release agents. The Poly 77 Series has been 

formulated to provide excellent abrasion and tear resistance for 

maximum mold life and performance. The high elongation characteristic 

of these rubbers enables easier demolding and reduces 

mold damage when used in demanding casting applications. 




CLEAN UP & SAFETY: See p. 33. 

FEATURES 

• High-performance, high-elongation rubbers 

• Hardnesses ranging from Shore A50 to A65 

• Easy-to-use formulations with 1:1 mix ratios 

• Easy demolding without damaging molds 

• Make tough, long-lasting molds 

PACKAGING 

Poly 77-50 and Poly 77-65 

Mix Ratio: 1A:1B (By Weight) 

PHYSICAL PROPERTIES 

77-50 77-65 

Mix Ratio, By Weight 1A:1B 1A:1B 

Hardness, Shore A 50 65 

Unit Weight 

(lb) 

Part A 

(lb) 


Part B 

(lb) 

Part A 

(Volume) 

Part B 

(Volume) 

Pour Time(min) 15 15 

Color Tan Tan 

Mixed Viscosity (cP) 1,200 1,600 

Specific Volume (in 3 /lb) 27.5 27.5 

4.0 

16.0 

80.0 

900 

2.0 

8.0 

40.0 

450 

2.0 

8.0 

40.0 

450 

1 qt 

1 gal 

5 gal 

55 gal 

1 qt 

1 gal 

5 gal 

55 gal 

Poly 81 Series RTV Liquid Rubbers 

DESCRIPTION: Use Poly 81 Series rubbers to make firm 

molds, mold facings, stamping tools, industrial parts, rollers, gaskets, 

mold shells, bumpers or pads. Poly 81 Series rubbers consist 

of liquid Part A and Part B that, after mixing, cure at room 

temperature to tough, durable rubbers. They offer low sensitivity 

to moisture, and low viscosity for easy vacuuming, if necessary. 


MIXING AND CURING: See p. 32. Parts A and B are clear liquids. 

The color of Part B may vary, but it has no effect on cured 

rubber properties. 



FEATURES 

• Firm rubbers ranging from Shore A90 to D45 

• Easy-to-use formulations 

• Reproduce fine details 

• Make tough, long-lasting molds, tools and parts 

PACKAGING 

Poly 81-Series 


81-90 81-D45 

Product 

(Mix Ratio) 

Unit 

Weight (lb) 

Component Weight (lb) 

Part A 

Part B 

Mix Ratio, By Weight 100A:40B 100A:20B 

Hardness (Shore A/D) A90 D45 

Pour Time (min) 23 19 

Demold Time (hr) 16 16 

Color Yellow Varies 

Mixed Viscosity (cP) 2,000 1,600 

Specific Volume (in 3 /lb) 26.6 26.4 

Poly 81-90 

(100A:40B) 

Poly 81-D45 

(100A:20B) 

11.2 

56.0 

280 

630 

9.6 

48.0 

192 

540 

8.0 

40.0 

200 

450 

8.0 

40.0 

160 

450 

3.2 

16.0 

80.0 

180 

1.6 

8.0 

32.0 

90.0 

38 

(610)559-8620 • (800)858-5990


Poly 72-40 Series RTV Liquid Rubbers 

DESCRIPTION: Poly 72-40 systems consist of liquid Part A and 

Part B that, after mixing in correct ratio, cure at room temperature 

to versatile mold rubbers. They may be poured or thickened and 

applied by trowel or brush, to make flexible molds. These molds 

are typically used for making wax castings in foundry applications. 

MODEL PREPARATION: See p. 32. CAUTION: Poly 72-40 

systems may be subject to cure inhibition by certain contaminants 

and may stick to some surfaces. See Technical Bulletin for details. 

MIXING AND CURING: See p. 32. See Technical Bulletin for 

details regarding mixing, curing and use of additives to thicken for 

brush-on application (e.g., fumed silica, Poly Fiber II, and Part D). 

USING THE MOLD: See p. 32 and Technical Bulletin. 

SOFTER MOLDS: Add Part C Softener to Part B before mixing 

with Part A. Consult Technical Bulletin for details. 

STORAGE: Poly 72-40 rubber remains usable for at least 6 

months from the date of shipment in unopened containers, stored in 

a cool, dry location. Cured molds slowly soften with age. Adequate 

mixing of components in the proper mix ratio contributes to long 

mold life as will storage of molds in a dark, cool, dry area. With 

proper care, Poly 72-40 molds should not soften appreciably for 2- 

4 years. Molds should be discarded before they become too soft to 

handle. Do not store molds outdoors, as exposure to sunlight and 

excessive humidity will cause rapid deterioration of the rubber. 


Mix Ratio, By Weight 

1A:10B 

Hardness, Shore A 40 

Pour Time (min) 30 

Cured Color 

Ivory 

Mixed Viscosity (cP) 4,000 

Specific Volume (in 3 /lb) 20 

Shrinkage Upon Cure 

Nil 

Unit Weight 

(lb) 

9.9 

49.5 

495 

PACKAGING 

Poly-Fast 72-40 and Poly 72-40 MF 

Mix Ratio 1A:10B (By Weight) 

Part A 

(lb) 

0.9 

4.5 

45.0 


Part B 

(lb) 

9.0 

45.0 

450 

Part A 

(Volume) 

1 pt 

½ gal 

5 gal 

Part B 

(Volume) 

1 gal 

5 gal 

55 gal 

Polyurethane 

Mold Rubber 

Poly GlassRub 50 RTV Liquid Rubber consists of two parts (A & 

B) that, after mixing, cure at room temperature to a flexible, clear 

rubber. Poly GlassRub 50 is designed for making clear molds that 

can be easily cut away from original objects with less chance of 

damage and better seam positioning since objects are visible 

through the rubber. Additionally, clear rubber castings or objects 

encapsulated in the clear rubber can make interesting original art 

or displays. Cured GlassRub may yellow slightly over time or following 

UV exposure. PolyColors can be added to the liquid rubber 

to make a tinted or colored, yet still clear, rubber. The smallest addition 

of a PolyColor virtually eliminates post-cure yellowing. 

For more information, consult the GlassRub Technical Bulletin. 


Poly GlassRub Liquid Rubber 

Mix Ratio, By Weight or Volume 

1A:1B 

Hardness, Shore A 45-50 

Pour Time, 1-lb mix (min) 45 

Demold Time (hr) 16 

Specific Gravity 1.0 

Color, Cured 

Glass Like/Blue-Clear* 

Viscosity, 2.5 min after mix (cP) 1000 

Specific Volume(in 3 /lb) 27.5 

* Upon exposure to UV light (i.e., fluorescent light or sunlight), cured 

rubber may yellow with age. 

FEATURES 

• Glass-like appearance (clear, pale blue) 

• Reproduces fine detail 

• Easy-to-use formulation -- 1A to 1B mix ratio 

• Low viscosity mix with excellent bubble-release 

• Long working time 

Unit Weight 

GlassRub 50 Liquid Rubber Packaging 

1A:1B Mix Ratio 

Weight 

Volume 

A (lb) B (lb) A B 

4 lb 2 2 1 qt 1 qt 

16 lb 8 8 1 gal 1 gal 

80 lb 40 40 5 gal 5 gal 

900 lb 450 450 55 gal 55 gal 


39

3 Silicone RTV Mold Rubbers 

Poly-Sil ® 

Silicone RTV Liquid Mold Rubbers 

Silicone 

Mold Rubber 

The Poly-Sil ® Silicone RTV Liquid Mold Rubbers each consist 

of a Part A and Part B, which, after mixing, cure at room 

temperature to flexible, high-strength, mold rubbers. Poly-Sil 

Mold Rubbers make molds that are easy releasing and stable at 

higher temperatures. They are excellent for casting plasters, 

waxes, cements, low melting metals and many resins such as 

epoxies, polyesters, urethanes and acrylics. 

As with other Polytek elastomers, the last two digits in the 

product name indicate the approximate Shore A hardness of the 

cured rubber. Poly-Sil rubbers range in hardness from a very soft 

A10 to a firm A60. 


Porous models such as wood or plaster should be sealed to 

prevent penetration of the rubber into the pores of the material. 

Wax, petroleum jelly, lacquer, paint and most other coatings are 

suitable sealers. Materials that will contact the rubber can be 

sprayed or coated with a light coat of Pol-Ease ® 2350, which 

functions as a sealer and release agent. Allow the Pol-Ease 2350 

to dry before applying liquid rubber. Silicone-based release 

agents (i.e., Pol-Ease ® 2300) are not to be used on surfaces that 

contact liquid Poly-Sil ® rubbers since inhibition and/or adhesion 

may occur. In addition, modeling clays containing sulfur may 

inhibit curing. In every case where there is any question about 

the compatibility between the rubber and the prepared model 

surface, a test cure should be made on an identical surface to 

determine that complete curing and good release are obtained. 

Poly-Sil rubbers may bond to cured silicone rubbers unless a 

parting agent is used. 

Porous models must be vented from beneath to prevent trapped 

air from forming bubbles in the rubber (see p. 12). 

MIXING AND CURING 

Before mixing rubber, be sure that both Parts A and B are at 

room temperature and that all tools and models are ready to go! 

Check product labels or technical bulletins to determine working 

time for the product -- some products set fast -- meaning that 

you must work quickly. 

Many Poly-Sil Part As require stirring before use. If there is a 

“Stir Before Use” label on the container -- be sure to do so. 

Molds made from highperformance 

Poly-Sil ® 

rubbers are best for casting 

harsh resins. This gargoyle 

blanket mold made of soft 

PlatSil ® 71-11 easily pulls 

off the cast resin part. The 

smooth, release-free 

demold of silicone is 

especially welcome on 

highly detailed parts. 

POLY-SIL ® MOLD RUBBERS: AT A GLANCE 

TinSil ® 70 Series - Tin-catalyzed silicone systems that 

cure to tough, high-performance rubbers with easy 

release properties and resistance to high temperatures. 

Great for casting polyester resin. 

PlatSil ® 71 Series - High-tear strength, platinum-cured 

silicone systems with hardness up to A40. Excellent for 

casting polyurethane resins and dimensionally accurate 

prototype parts. 

PlatSil ® 73 Series - High-tear strength, tough, platinumcured 

silicone systems with hardness up to A60. 

Excellent for casting polyurethane foams and 

dimensionally accurate prototype parts. 

PlatSil ® Gel 10 - A soft, translucent rubber for delicate 

casting projects and special effects applications. 


you are using. For Poly-Sil rubbers, most mix ratios are 

expressed by weight. Carefully weigh Parts A and B in proper 

ratio. Accurate weighing is essential to obtain optimum physical 

properties from the cured rubber. Weigh Part B into a clean 

metal or plastic mixing container. Then weigh the appropriate 

amount of Part A into the same container. Mix thoroughly, 

scraping sides and bottom of the container. Hand mixing with a 

Poly Paddle (see p. 62) is best to avoid mixing air into the rubber. 

To ensure a bubble-free mold, deaerate the liquid rubber under 

vacuum at 28-29 inches mercury until the mass of rubber rises 

and then collapses. Deaerate for an additional 2 minutes. For 

vacuuming, use a mixing container 3 to 4 times larger than the 

volume of rubber. Pour the rubber as soon after mixing as possible 

for best flow and air bubble release. 

If reinforcement of the rubber is needed (i.e., in thin blanket 

molds), place stretchy, open mesh nylon or dacron cloth into the 

uncured rubber. Be sure that the fabric is not too close to the 

mold surface or the weave of the cloth may show through to the 

face of the mold. 

Check product labels or technical bulletins to determine cure 

times. To reach full hardness in the specified demold time, 

temperature should be above 77°F (25°C). At lower temperatures, 

more time may be needed to reach full hardness. Curing below 

65°F (18°C) is not recommended. For most Poly-Sil products, 

final cure properties are obtained in about seven days, but most 

molds may be used with care after curing for 24 to 48 hours. 


No release agent is necessary for casting most materials in Poly- 

Sil molds. For longer mold life, however, a barrier coat or release 

agent (i.e., Pol-Ease ® 2300) is recommended when casting epoxy, 

40 

(610)559-8620 • (800)858-5990

Silicone RTV Mold Rubbers 3 

polyurethane or polyester resins. Most Poly-Sil molds can be 

stored for years, but tin-catalyzed silicone molds eventually 

deteriorate and lose their elasticity. 


Polytek offers various additives that can be used to vary the 

properties of the cured and uncured Poly-Sil rubbers. 

• Thinner/Softener - Very low viscosity 50 cSt Silicone Fluid 

can be added sparingly to the mixed rubber to thin the mix 

with some loss of strength, hardness and cure speed. More 

than 10% fluid addition may exude from the cured rubber. 

• Accelerator - A specially formulated accelerator can be 

added to most Poly-Sil products to reduce the cure time. 

• Thickener - Specially formulated chemical thickeners can 

be added to most Poly-Sil products to make the liquid 

rubber thicker (i.e., for brush-on application). Cab-O-Sil ® 

Fumed Silica, which is both a thickener and thixotropic 

agent, can also be added to mixed Parts A and B in order to 

form a gel appropriate for application by brush or trowel. 

• Colors - Certain Poly-Sil rubbers can be tinted to various 

shades by adding small amounts of colors. 

• Barrier Coat - A barrier coat (i.e., Barrier PF) is a fast 

drying, lacquer-like primer that is sprayed into a silicone 

mold and allowed to dry prior to pouring plastic. The 

plastic cures against the barrier coat and comes out on the 

plastic casting resulting in a pre-primed part. Using a 

barrier coat may extend mold life. 

To learn more about additives, refer to product technical 

bulletins or call Polytek Customer Service. See additives and 

accessories for Poly-Sil products in the box to the right. 

CLEAN UP 

Tools should be wiped clean before the rubber cures. Denatured 

ethanol is a good cleaning solvent, but it must be handled with 

extreme caution owing to its flammability and health hazards. 

SAFETY 



products may cause eye, skin and/or respiratory irritation. Avoid 

contact with skin and eyes. If skin contact occurs, remove with 

waterless hand cleaner or alcohol then soap and water. In case of 

eye contact, flush with water for 15 minutes and call a 

physician. Use only with adequate ventilation. Poly-Sil products 

are not to be used where food or body contact may occur. 

STORAGE LIFE 

At least six months in unopened containers stored at room 

temperature (60-90°F). 

TINSIL & PLATSIL ACCESSORIES 


12-oz can, case of 12 cans 


1 qt (1.5 lb), 5 gal (26 lb) 


12-oz can, case of 12 cans 

Silicone Fluid 50 cSt Grade 

For Thinning Poly-Sil ® Rubbers 

1 qt (2 lb), 1 gal (8 lb), 5 gal (40 lb) 

TinSil ® FastCat 

4 oz, 1 pt (1 lb), 1 gal (8 lb) 

TinThix 

4 oz, 1 pt (1 lb) 

PlatSil ® 71/73X Accelerator 

4 oz, 1 pt (1 lb), 1 gal (8 lb) 

PlatSil ® 71R Retarder 

4 oz, 1 pt (1 lb), 1 gal (8 lb), 5 gal (40 lb) 

PlatThix 

4 oz, 1 pt (1 lb) 

Barrier PF 

1 qt (1.5 lb), 5 gal (35 lb) 

Cab-O-Sil ® /Fumed Silica 

5 gal, 1 bag (10 lb) 

Smith’s Theatrical Prosthetic Deadener 

1 qt (2 lb), 1 gal (8 lb), 5 gal (40 lb) 

Silicone 

Mold Rubber 

CAUTION! -- Certain chemicals cause cure 

inhibition in silicone rubbers. Beware of amines, 

polyesters and tin compounds with PlatSil 

systems. Sulfur compounds can affect both 

PlatSil and TinSil systems. Perform a test cure! 

Poly-Sil ® rubber blanket molds reproduce the fine details of models 

and are soft and tough enough to easily pull off complex castings. 

Usually, the more intricate the model/casting, the softer the mold 

rubber selected. This very ornate column capital was easily cast 

in TinSil ® 70-11. The gargoyle mold was made using PlatSil ® 71- 

20. The large, multi-piece, Ronald McDonald ® mold was made 

using TinSil ® 70-30 to cast numerous polyester resin parts. 


41


TinSil ® 

70 Series 

Silicone 

Mold Rubber 

DESCRIPTION: TinSil ® 70 Series RTV Silicone Rubbers are 

condensation-cure, tin-catalyzed, flexible mold rubbers. TinSil 

products consist of a liquid Part B base and Part A accelerator, 

which, after mixing at the proper ratio by weight, cure at room 

temperature to rubber with a tough, knotty tear property. TinSil 

molds have easy release properties and are resistant to high 

temperatures. TinSil molds are excellent for casting polyesters, 

epoxy and polyurethane resins; waxes and many other materials. 

Choose the appropriate hardness of rubber for your application. 

• TinSil 70-11, 70-20 and Gel-10 are soft and, therefore, best 

for delicate castings. Gel-10 is translucent and especially 

useful for animatronics and special effects. 

• TinSil 70-25 and 70-30 are Polytek’s most popular and 

versatile, mid-range hardness, silicone rubbers. 

• TinSil Spray-25 is sprayable or brushable and can be 

applied by hand or sprayed with a low-cost Plas-Pak spray 

gun or more sophisicated 1A:10B silicone spray equipment. 

Spray 25 is great for large scale blanket molds! 

• TinSil 70-39 is firm with excellent tear properties making it 

popular for casting polyurethane foams and plastic prototypes. 

• TinSil 70-60 is stable at higher temperatures making it 

suitable for casting low melting metals. TinSil 70-60 has 

limited tear strength because of its hardness. 


MIXING AND CURING: See p. 40. CAUTION! TinSil products 

release alcohol while curing, which results in slight shrinkage of 

the rubber (up to 1%) and can inhibit the surface cure of some 

polyurethanes. If shrinkage cannot be tolerated, consider PlatSil 

rubbers. Before casting polyurethanes in a TinSil mold, evaporate 

alcohol by letting the mold sit in a warm location for 24 hours or 

by baking the mold for 4 hours at ~200°F. 

USING THE MOLD: See p. 40. [Note: Molds made with excess 

catalyst may be subject to faster degradation on aging.] 

ACCELERATING CURE SPEED: Use TinSil FastCat in place 

of any TinSil Part A in order to accelerate cure and shorten 

demold time. FastCat can be used in a range of 2-6 parts per 100 

parts B; see product technical bulletin for details. Use of FastCat 

can shorten the library life of cured TinSil rubber. 

THICKENING FOR BRUSH ON: Add TinThix liquid 

thickener or Cab-O-Sil ® to liquid TinSil rubbers for brushing on 

a blanket mold. TinThix can be mixed into the Part B (before 

mixing with Part A) to achieve varying levels of thixotropy. 

ACCESSORIES: See box on p. 41. 


TinSil Physical Properties 

70-11 & Gel-10 70-20 70-25 Spray-25 70-30 70-39 70-60 

Mix Ratio (By Weight) 1A:10B 1A:10B 1A:10B 1A:10B 2A:100B 1A:10B 5A:100B 

Hardness, Shore A 10 20 25 25 30 40 60 

Pour Time (min) 45 60 60 30 60 45 30 

Demold Time @ 77°F (hr) 16 16 16 16-24 24 16 24 

Color Blue (70-11) Blue Blue Translucent Beige Blue Red 

Transluscent (Gel-10) 

Mixed Viscosity (cP) 10,000 10,000 14,000 Thixotropic 26,000 25,000 17,000 

Specific Volume (in 3 /lb) 25.3 25.3 25.3 25.3 25.3 21.7 18 

Specific Gravity 1.1 1.1 1.1 1.1 1.1 1.27 1.5 

Shrinkage Upon Cure (%) ~0.3 ~0.3 ~0.3 ~0.3 ~0.3 ~0.3 ~0.8 

TinSil Product 

Gel-10, 70-11, 70-20, 70-25, Spray 

25 and 70-39 

Mix Ratio 1A:10B 

70-30 


70-60 


TinSil Packaging 

Unit Sizes (lb) Part A (lb) Part B (lb) 

1.0 

2.0 (Spray 25 Cartridge) 

9.0 

44.0 

495 

1.02 

8.3 

40.8 

448.8 

1.05 

8.4 

42.0 

0.1 

0.2 

0.9 

4.0 

45.0 

0.02 

0.2 

0.8 

8.8 

0.05 

0.4 

2.0 

0.9 

1.8 

8.1 

40.0 

450 

1.0 

8.1 

40.0 

440 

1.0 

8.0 

40.0 

42 

(610)559-8620 • (800)858-5990


PlatSil ® 

71 Series 

DESCRIPTION: PlatSil ® 71 Series RTV Silicone Rubbers are 

two-component, addition-cure, platinum-catalyzed, flexible mold 

compounds. The 71 Series products exhibit a tough, knotty tear, 

making them especially valuable to the mold making industry. 

They are excellent mold materials for casting polyester, epoxy 

and polyurethane resins, as well as for waxes and many other 

materials. PlatSil 71 Series products offer advantages over tincatalyzed 

systems in certain applications because on curing they 

don’t shrink and don’t produce alcohol (like tin-catalyzed 

silicones), which can inhibit polyurethane castings. 


MIXING & CURING: See p. 40. 


ACCELERATING CURE SPEED: Accelerate the cure with heat 

or the addition of PlatSil 71/73X. Mix 71/73X with Part B prior 

to adding Part A. Weigh and add Part A to the accelerated Part B 

mixture and mix thoroughly. Pour over a properly prepared 

model as soon after mixing as possible. The addition of 1 part 

71/73X per 100 parts of Part B decreases the gel time to ~1/3 the 

normal gel time. The addition of 2 parts decreases the normal gel 

time to ~1/4. The addition of 3 parts decreases the normal gel 

time to ~1/6. Experimentation on a small scale is recommended 

before making a larger mix. 

FEATURES 

• Easy mix ratios; some 1:1 mixes available 

• Cure at room temperature or accelerate with heat 

• Easy release properties -- save on release agents 

• High tear strength -- fewer prematurely torn molds 

• Good chemical resistance for longer mold life 

• Low/zero shrinkage for dimensional reproduction 

• Range of hardnesses from A10 to A40 

RETARDING CURE SPEED: PlatSil 71R added to PlatSil 

Part A prior to mixing with Part B slows the cure yielding longer 

working time and longer demold time. Adding ~1% of 71R to 

the total mixed weight of PlatSil A+B roughly doubles the 

working time. Adding ~2% of 71R triples working time. Do not 

use more than 4% as the system may not cure at all. 

THICKENING FOR BRUSH ON: For brushing on skin mold, 

thicken PlatSil 71 Series rubbers with PlatThix or Cab-O-Sil. 

When brushing PlatSil 71-11 or 71-20, apply subsequent coats to 

the previous layer within one hour to obtain best adhesion. 



Silicone 

Mold Rubber 


71-10 71-11 71-20 71-30 71-35 71-40 

Mix Ratio (By Weight) 1A:10B 1A:1B 1A:1B 1A:10B 1A:10B 1A:5B 

Hardness, Shore A 10 10 20 30 35 40 

Pour Time (min) 5 20 25 60 60 60 

Demold Time (hr) @ 77°F 0.5 4 4 24 24 24 

Color Pink Blue Green Lt. Purple Lt.Green Blue Hazy transparent 

Mixed Viscosity (cP) 3,500 6,000 12,000 25,000 25,000 25,000 

Specific Volume (in 3 /lb) 26 24.7 24.7 24.7 24.7 25 

Specific Gravity 1.06 1.12 1.12 1.12 1.12 1.10 

Shrinkage Upon Cure Nil Nil Nil Nil Nil Nil 

PACKAGING 

Product Unit Weight Size Net Weight (lb) 

(lb) A B A B 

PlatSil ® 71-11, 71-20 2.0 1 pt 1 pt 1.0 1.0 

Mix Ratio 1A:1B 16.0 1 gal 1 gal 8.0 8.0 

80 5 gal 5 gal 40.0 40.0 

PlatSil ® 71-10, 71-30, 71-35 1.0 4 oz 1 pt 0.1 0.9 

Mix Ratio 1A:10B 9.0 1 pt 1 gal 0.9 8.1 

44.0 ½ gal 5 gal 4.0 40.0 

495 6 gal 55 gal 45.0 450 

PlatSil ® 71-40 9.8 1 qt 1 gal 1.7 8.1 

Mix Ratio 1A:5B 48.0 1 gal 5 gal 8.0 40 

528 2 x 6 gal 55 gal 88 440 


43


PlatSil ® 

73 Series 

Silicone 

Mold Rubber 

DESCRIPTION: PlatSil ® 73 Series RTV Silicone Rubbers are 

two-component, high-tear strength, flexible mold compounds. 

The 73 Series rubbers are excellent mold materials for many 

casting materials including polyester, epoxy and polyurethane 

resins. PlatSil 73 Series silicones are addition-cure, platinumcatalyzed 

systems and offer advantages over tin-catalyzed 

systems in certain applications because on curing they don’t 

shrink, they don’t produce alcohol, which can inhibit urethane 

castings, and their cure can be heat accelerated. 


MIXING & CURING: See p. 40. 


ACCELERATING CURE SPEED: Accelerate the cure with 

heat or the addition of PlatSil 71/73X. Weigh and add 71/73X to 

Part B and mix. Weigh and add Part A to the accelerated Part B 

mixture and mix thoroughly. Pour over a properly prepared 

model as soon after mixing as possible. Demold when tack free. 

The addition of 1 part 71/73X per 100 parts of Part B decreases 

the gel time to ~35 min. The addition of 2 parts decreases the gel 

time to ~30 min. The addition of 3 parts decreases the gel time to 

~25 min. The addition of 71/73X softens the cured rubber 

slightly. Remember, heat accelerates the cure; low temperatures 

slow the cure. 

FEATURES 

• Low viscosity for excellent detail reproduction and 

easy degassing. 

• Easy 10A:100B mix ratio -- can use with 

dispensing machines 

• Cure at room temperature or accelerate with heat 

• Easy release properties -- save on release agents 

• High tear strength -- fewer prematurely torn molds 

• Good chemical resistance for longer mold life 

• Low/zero shrinkage for better dimensional 

reproduction 

• Range of hardnesses from A30 to A60 

THICKENING FOR BRUSH ON: PlatSil 73 Series rubbers can 

be thickened with PlatThix liquid thickener or with Cab-O-Sil ® 

for brushing on a blanket mold. 




73-29 73-45 73-60 

Mix Ratio, By Weight 10A:100B 10A:100B 10A:100B 

Hardness, Shore A 30 45 60 

Pour Time (min) 45 60 45 

Demold Time @ 77 o F (hr) 16 16 16 

Color White Green Blue 

Mixed Viscosity (cP) 15,000 35,000 40,000 

Specific Volume (in 3 /lb) 25.0 21.3 21.3 

Specific Gravity 1.10 1.30 1.30 

Shrinkage Upon Cure Nil Nil Nil 

PACKAGING 

PlatSil ® 73-29, 73-45, 73-60 


Unit Weight 

Components 

(lb) Size Net Weight (lb) 

A B A B 

1.0 4 oz 1 pt 0.1 0.9 

9.0 1 pt 1 gal 0.9 8.1 

44.0 0.5 gal 5 gal 4.0 40.0 

495 (73-29) 6 gal 55 gal 45.0 450 

550 6 gal 55 gal 50.0 500 

44 

(610)559-8620 • (800)858-5990

PlatSil ® Gel-10 


DESCRIPTION: Platil ® Gel-10, a translucent, soft rubber, is an 

excellent mold material for delicate casting projects and creating 

special effects. Gel-10 is a two-part, addition cure, liquid silicone 

system with an easy 1:1 mix ratio. After mixing Parts A and B, 

Gel-10 cures within 30 minutes at room temperature to a soft, 

tough rubber. Gel-10 does not shrink on curing. 

For special effects, soften PlatSil Gel-10 by adding Smith’s 

Theatrical Prosthetic Deadener. “Deadened” PlatSil Gel-10 is 

excellent for creating skins and self-sticking appliances. 


MIXING AND CURING: See p. 40. Normal mixes gel in 

approximately 6 minutes at room temperature; faster if warm, 

slower if cold. Immediately place the mix over the model or in 

the mold. There is not normally adequate time for vacuum 

(unless retarder is used), but pressure casting may be useful to 

eliminate bubbles. 

Contamination with soaps, amines, sulfur, tin compounds and 

some RTV Silicone Rubbers may inhibit surface cure. 

USING THE MOLD: For best results, allow PlatSil Gel-10 to 

cure for at least 1 hour before use. No release agent is necessary 

for casting most materials in properly cured PlatSil Gel-10. For 

longer mold life, however, use a barrier coat or release agent 

when casting epoxy, polyurethane or polyester resins. 

ACCELERATING CURE SPEED:Mix PlatSil 71/73X into 

Part B prior to adding Part A to accelerate gel time and cure. See 

product technical bulletin for details. 

RETARDING CURE SPEED: Add PlatSil 71R to Part A prior 

to mixing with Part B to slow the cure for longer working time 

and demold time. Add 71R at 1% of the weight of total mix 

(A+B) to double the working time. Add up to 5% for a 60- 

minute work time with 120-minute demold time. 

THICKENING FOR BRUSH ON: Thicken with TinThix liquid 

thickener or with Cab-O-Sil ® for brush-on application. Add 1% 

TinThix to the total mix weight for a light-bodied, non-sag gel. 

SMITH’S THEATRICAL PROSTHETIC DEADENER: Add 

up to 250% of Smith’s Deadener to the total Gel-10 mix weight 

(A+B) to create super soft, gel-like, self-sticking prosthetics or 

gel-filled appliances. If applied behind a casting of straight 


Mix ratio, by weight 

1A:1B 

Hardness, Shore A 10 + 2 

Pour time, minimum 

6 min 

Demold time @ 25°C (77°F) 

30 min 

Color 

Colorless 

Viscosity, mixed 

15,000 cP 

Specific volume (in 3 /lb) 25 

Specific gravity @ 25°C (77°F) 1.10 

Shrinkage upon cure 

Nil 


FEATURES 

• Soft (~A10), translucent, silicone rubber 

• Easy 1:1 mix ratio 

• Fast 30-minute demold with 6-minute work time 

• PlatSil ® 71R Retarder slows the cure 

• PlatSil ® 71/73X Accelerator speeds the cure 

• PlatThix thickens the mix to a brushable paste 

• Bonds to Poly Plastics 

PlatSil Gel-10, the underlying gel can mimic the slow stretch and 

recovery properties of human tissue. Pigments can be added to 

PlatSil Gel-10 and/or Deadener to achieve any color needed. 

The term “deadener” was coined by Gordon Smith of FXSmith, who 

developed this additive. Deadened Gel-10 does not have the springy, 

snappy feel typical of silicone rubber, but rather resembles the feel of 

human tissue. Go to www.fxsmith.com for more information. 

BONDING TO PLASTICS: PlatSil Gel-10 bonds to clean, 

cured Poly 15 Series plastics that are less than 24-hours old. See 

product technical bulletin for details. 



Unit Weight 

PACKAGING 

Mix Ratio: 1A:1B (By Volume) 

David Gavin and 

colleagues from Arran 

Studios in Cork, Ireland, 

proudly display their 

Velociraptor casting made 

with life-like PlatSil ® Gel-10 

skin. 

PlatSil ® Gel-10 makes 

great animatronic skins. 

The product can be 

softened with the addition 

of Silicone Fluid and 

colored to make the look 

and feel just right. 

Containers 


A B A B 

2.0 1 pt 1 pt 1.0 1.0 

16.0 1 gal 1 gal 8.0 8.0 

80.0 5 gal 5 gal 40.0 40.0 

Silicone 

Mold Rubber 

45

4 Casting Plastics/Resins 

Casting & Mold Shell Plastics 


Polytek liquid plastics are two-part systems that can be used to 

cast decorative objects, parts, tools, and patterns as well as to create 

lightweight mold shells to support brushed or sprayed blanket 

molds. Polytek plastics can mimic materials of nearly any density 

and appearance including lightweight foams, thermoplastics, 

glass, wood, stone and metals. The products can be poured, layed 

up or sprayed to accommodate any size casting or object. Varying 

viscosities, pot-lives, cure times and physical properties allow the 

user to choose a plastic tailored to their particular needs. The versatility 

of Polytek Plastics is unlimited. 

MOLD PREPARATION 

Before pouring or applying liquid casting plastics, be sure that the 

surface is properly prepared in order to prevent the plastic from 

sticking or foaming. Polyethylene and silicone rubber molds, such 

as TinSil ® and PlatSil ® products, do not require a release agent, but 

a barrier coat may be helpful. Latex, polyurethane rubber or metal 

molds must be dry and require a coat of Pol-Ease ® 2300 Release 

Agent. A trial casting or application should be made to avoid damaging 

a valuable mold and/or wasting liquid plastic. 

When using Poly Plastics to create lightweight mold shells, prepare 

the rubber mold surface as described on p. 20. Poly 15-6, 

1511 and Poly 1512X can be mixed with Poly Fiber to thicken the 

pourable plastics to a thixotropic consistency that can be applied 

to vertical and horizontal surfaces like frosting a cake. This 

process is described in more detail on p. 22. 

MIXING 

Before mixing resins, be sure that both Parts A and B are at room 

temperature and that all tools and molds are ready to go! Use 

metal or plastic mixing vessels (i.e., polyethylene pail) and spatulas 

to avoid introducing moisture. Check product labels or technical 

bulletins to determine working time for the product -- some 

products set fast -- meaning that you must work quickly. Some 

Polytek plastics require stirring before use. If there is a “Stir 

Before Use” label on the container -- be sure to do so. 


you are using. Carefully weigh/measure Parts A and B in proper 

ratio. Accurate weighing/measuring is essential to obtain optimum 

physical properties from the cured plastic. Weigh/measure 

Part B into a clean metal or plastic mixing container. Then 

weigh/measure the appropriate amount of Part A into the same 

container. Mix thoroughly, scraping sides and bottom of the container. 

Hand mixing with a Poly Paddle (see p. 62) is best to avoid 

mixing air into the plastic. Pour mix into mold cavity or apply to 

surface as soon after mixing as possible. 

Once the containers of Parts A and B are opened, they should be 

used completely or resealed tightly as atmospheric moisture can 

react with the Part A or may cause foaming of the plastic. Poly 

Purge , a dry gas product, can be sprayed into opened containers 

of liquid plastics to lengthen shelf life once opened. 

POLYTEK PLASTICS: AT A GLANCE 

EasyFlo Series - Low viscosity, 1:1 mix by volume, 

fast-setting plastics. Polytek’s easiest-to-use and bestselling 

plastics! 

Poly 15-Series - Strong plastics with varying densities: 

some are like thermoplastics, others like stone. 

Poly PT Series - Strong, fast-curing, flame-retardant 

plastics for prototyping and model making. Also available 

in low-viscosity, fast-curing rubber formulations. 

Request Technical Bulletin for details. 

Poly-Optic ® 14 Series - Water clear, non-yellowing casting 

resins for speciality applications demanding clear, 

bubble-free castings. 

PolyFoam Series - Low viscosity, 1:1 mix ratio, fastsetting 

rigid and flexible foams. 

Poly LiteCast - Easy, 1:1 mix ratio plastic with a woodlike 

density. 

Poly Plasti-Flex - Innovative flexible plastic for architectural 

moldings that bend, props and more. 

Polygel ® Plastic-75 - Thickens to a paste upon mixing 

and cures in 2-4 hours. Makes great mold shells fast. 

Polygel ® Shell - A sprayable plastic for creating mold 

shells, sprayed-up castings or surface hardcoats. 

Polypoxy ® Resins & Poly Cures - Epoxy systems for 

creating various castings including decorative bonded 

bronzes and tools that can withstand high heat. 

CURING 

Castings should be allowed to remain in the mold until thoroughly 

cured. Parts demolded too soon may be subject to deformation. 

Use of pre-warmed molds will hasten curing. Mold shells should 

not be demolded until fully cured to prevent distortion or warping. 

Check product labels or technical bulletins to determine appropriate 

demold times. To reach full hardness in the specified demold 

time, temperature should be above 77°F (25°C). At lower temperatures, 

more time may be needed to reach full hardness. Curing 

below 65°F (18°C) is not recommended. For most Polytek plastics, 

final cure properties are obtained in within 7 days. 


Polytek offers various additives and accessories that can be used 

to vary the properties of the cured plastics and/or make using the 

plastics easier. 

• Accelerator/Retarder - Specially formulated chemical accelerators 

or retarders can be added to Polytek liquid plastics to 

vary the cure time. 

• Fillers - Dry fillers or metal powders can be added to Polytek 

liquid plastics to vary the density and look of the cured pieces. 

Also, fillers can be added to make the liquid plastic thicker 

(i.e., for brush-on or trowel application). 

46 

(610)559-8620 • (800)858-5990

• Foamer - A chemical foamer can be added to some liquid 

plastics to turn them into foams. 

• Colors - PolyColors can be added to liquid plastics (see p. 61). 

• Barrier Coat - A barrier coat (i.e., Barrier PF) is a fast drying, 

lacquer-like primer that is sprayed into a silicone mold and 

allowed to dry prior to pouring plastic. The plastic cures 

against the barrier coat and comes out on the plastic casting 

resulting in a primed part. Using a barrier coat often extends 

mold life. 

To learn more about additives, refer to product-specific technical 

bulletins or call Polytek Customer Service. Additives and accessories 

for Polytek plastics are listed in the box to the right. 

FINISHING 

Many cured plastics yellow slightly and chalk when exposed to 

sunlight and, therefore, should be painted or sealed for exterior 

use. If they are to be painted or coated, adhesion of the coating 

should be checked carefully over a period of time to determine 

that it is satisfactory for the intended use. If all mold release is 

removed by detergent washing, most oil paints work well. 

Castings can be drilled, sanded and machined. 

CLEAN UP 

Tools should be scraped clean before the plastic is hard. 

Denatured ethanol is a good cleaning solvent, but it must be handled 

with extreme caution owing to its flammability and health 

hazards. Work surfaces can be waxed or coated with Pol-Ease 

2300 Release Agent so cured rubber can be removed. 

SAFETY 



products may cause eye, skin and/or respiratory irritation. Avoid 

contact with skin and eyes. If skin contact occurs, remove with 

waterless hand cleaner or alcohol then soap and water. In case of 

OTHER SUPPLIERS FOR FILLERS 

3M - Lightweight fillers, Glass Bubbles 

(800) 541-6752 

Ball Consulting ltd - Brass, copper and silver powders 

(800) 225-2673 

Imerys Inc. (formerly Georgia Marble Co.) - Marble powders 

(888) 277-9636 

Mahogany Co. - Various fillers 

(609) 625-8101 

PQ Corp. - Lightweight fillers, Extendospheres, Q-cells 

(800) 252-0039 

The R.J. Marshall Co. - Aluminum Tihydrate, OnyxFill, etc. 

(248) 353-4100 

Trelleborg Fillite Inc. - Hollow ceramic microspheres 

(770) 729-8030 

Casting Plastics/Resins 4 

eye contact, flush with water for 15 minutes and call a physician. 

Use only with adequate ventilation. Polytek plastics are not to be 

used where food or body contact may occur. Plastics burn readily 

when ignited. Care should be taken with sanding dust and other 

easily ignitable forms of these products. 

STORAGE LIFE 

Polytek liquid plastics can be stored for at least six months in 

unopened containers stored at room temperature (60-90°F). Cured 

plastics will last indefinitely, but may discolor as noted above. 

In order to maintain dimensions, Poly Plastic mold shells must be 

stored in temperatures



EasyFlo Series Liquid Plastics 

DESCRIPTION: EasyFlo Liquid Plastics are excellent for casting 

decorative objects, production parts, tools, models, duplicate 

masters and more. EasyFlo systems consist of two parts (A and B) 

that, after mixing, quickly cure to tough polyurethane plastics. 

Since Parts A and B are super- low viscosity liquids, they are easy 

to mix, provide excellent detail penetration, and make bubble-free 

castings without vacuum degassing or pressure casting techniques. 

Rapid demold times make EasyFlo ideal for high-volume, fastcast 

applications. Choose the EasyFlo Liquid Plastic that’s best for 

your application: 

• EasyFlo 60 pours like water, so making bubble free parts is 

easy and fast (2-min working time, 10-min demold). 

• EasyFlo 95 is useful when longer working time (5 min) is 

needed to complete a pour. For thin parts, demold time is 

longer and molds may need to be preheated (100-120°F) to 

reduce surface bubbles and speed demold. 

• EasyFlo 120 is best for rotocasting or slush casting to create 

hollow parts. Hollow parts are nearly unbreakable! 

• EasyFlo Clear cures to a pale amber color. Add PolyColors to 

make transparent, colored castings. It’s excellent in applications 

using fillers intended for visual appeal (e.g., bronze). Heated 

molds and pressure casting techniques are recommended. 

MOLD PREPARATION: See p. 46. 

MIXING: Measure equal volumes of A and B into a mixing container 

such as a polyethylene pail. Mix immediately and thoroughly 

for one minute. See p. 46 for more information. 


EasyFlo Product 60 95 120 Clear 

Mix Ratio, By Volume 1A:1B 1A:1B 1A:1B 1A:1B 

Mix Ratio, By Weight 100A:90B 100A:90B 100A:90B 100A:90B 

Hardness, Shore D 65 65 65 72 

Pour Time (min; 1-lb mix) 2-2.5 5 2-2.5 2-2.5 

Demold Time (min) 15-30 20-60 15-30 15-30 

Specific Gravity 1.03 1.03 1.03 1.03 

Cured Color White Off White White Amber 

Initial Mixed Viscosity (cP) 60 95 120 110 

Specific Volume (in 3 /lb) 26.9 26.9 26.9 26.9 

Maximum Exotherm (°F) 230 206 200 208 

PACKAGING 

Product(s) Part A (lb) Part B (lb) Unit 

EasyFlo 60, 95, 

120, & Clear 

1 qt (2.0) 

1 gal (8.0) 

5 gal (40.0) 

55 gal (450) 

1 qt (1.8) 

1 gal (7.2) 

5 gal (36.0) 

55 gal (405) 

3.8 lb 

15.2 lb 

76.0 lb 

855 lb 

FEATURES 

• Easy 1:1 mix ratio by volume 

• Extremely low viscosity -- pours like water 

• Sets fast with rapid demold 

• Reproduces finest details 

• Tough, non-brittle formula 

• Excellent bubble release without vacuum or pressure 

• Readily accepts high filler levels 

• Low odor 

CURING: See p. 46. 

ADDITIVES: Various fillers (bronze powder, microballoons, calcium 

carbonate, sand, granite, etc.) can be added as desired. Fillers 

must be thoroughly dried before mixing with resin. 

PolyColors (see p. 61) can be added to EasyFlo Part B before mixing 

with Part A to create plastic of any color desired. 

FINISHING: See p. 47. 



These bronze castings were 

created quickly and easily by 

mixing bronze powder with 

EasyFlo 60 Liquid Plastic. 

Large castings such as this 

10-inch tall Zeus head can be 

rotocast with EasyFlo 120 to 

create hollow parts weighing a 

fraction of the weight of solid 

castings. 

Note on Cold-Cast Bronze 

Bronze and other metal powders are rather expensive; but only a thin 

coating of resin mixed with bronze need be brushed or slush-cast 

against the face of the mold. Estimate the volume of liquid resin and 

bronze required by considering the surface area to be covered by the 

thinnest possible layer. If needed, multiple mixes can be made and 

patched one against the other before they fully cure. The recipe for 

the EasyFlo 60/bronze powder mix is as follows. Mix 1 part (by volume) 

EasyFlo 60 A with 1 part (by volume) EasyFlo 60 B and blend 

for a few seconds. Then add 2 parts (by volume) bronze powder to 

the mixed EasyFlo and mix well to wet the powder. This mix will be 

thick and may not flow into all the mold detail, so brushing may be 

needed. Once the face of the mold is evenly coated with a thin layer 

of resin/bronze it can be back-filled with a heavy, solid pour resin 

such as 15-3X. 15-3X resin will make it "feel" like bronze without 

the cost of filling the entire space with expensive bronze powder. 

Once cured, the casting can be removed and burnished with 0000 

steel wool. Apply a patina by spraying green and black oil-based 

paint and wiping with mineral spirits or use a cold chemical patina 

such as Super Antik 40. The results can be amazing! 

48 

(610)559-8620 • (800)858-5990

Poly 15 Series Liquid Plastics 


DESCRIPTION: Poly 15 Series Liquid Plastics are excellent for 

casting decorative fixtures, production parts, tools, models, patterns, 

duplicate masters, mold shells and more. Poly 15-6, 1510, 

1511, 1512 and 1512X Plastics have the feel and density of wood 

or thermoplastics. Poly 15-3 and 15-3X Plastics resemble stone. 

Poly 15-8 is an aluminum-filled system that is ideal for applications 

where heat resistance and thermal conductivity are required 

(i.e., vacuum forming). Poly 15-6, 1511 and 1512X can be mixed 

with Poly Fiber II to create tough, lightweight mold shells. With 

proper equipment and acceleration, Poly 1512 can be sprayed for 

hardcoating or to make sprayed-up castings. If water-clear, non-yellowing 

plastics are needed, consider Poly-Optic ® products (p. 51). 


MIXING: See p. 46. 

CURING: See p. 46. 

ADDITIVES: Part 15X Catalyst increases the speed of curing (see 

box on next page). Stir Part X into Part B before adding Part A. A 

few drops in a 1-lb mix speeds the cure significantly. Exotherm 

(heat of reaction; see p. 6) and thus shrinkage may be increased. 

Experiment to determine the best amount of Part X to use, but 

never use more than 1% Part X of the total weight of the mix or 

the final physical properties may be affected. 

Part 15F Foamer can be added to Poly 15-6 and 1510 to create 

rigid, open-cell foams with densities as low as 6 lb/ft 3 . Part F 

Foamer should be stirred into the Part B before adding Part A. 

Experiment to determine the best amount of Part F for the application 

at hand, but never use more than 3% Part F of the total 

weight of the mix or the final physical properties may be affected. 

For self-skinning foams, consider PolyFoam products (see p. 53). 

If a paste-like consistency is needed for application, add Poly 

Fiber II to thicken the mix 

FEATURES 

• Easy -- 1:1 mix ratio formulations 

• Reproduces fine details 

• Can be machined, drilled, sanded 

• Tough and hard, but not brittle 

• Lightweight for mold shells 

• Low shrinkage upon cure 

• Air bubbles rise and break 

• Long working time or instant set with 15X 

• Low odor formula 

• Castable in large masses 

• Sprayable for hardcoating 

Add fillers as needed to vary the density and appearance of the 

cured plastic. Microballoons can be added to create a wood-like, 

density. Other fillers include metal (e.g., bronze) or stone (e.g., 

calcium carbonate) powders. Add fillers after Parts A and B are 

mixed. Fillers must be thoroughly dried before mixing with resin. 

PolyColors (see p. 61) can be added to some 15 Series Part Bs 

before mixing with Part A to create colored plastics. 

FINISHING: See p. 47. 

STORAGE: In order to maintain dimensions, Poly Plastic mold 

shells must be stored in temperatures


Polytek ® is proud to share 

its hometown, Easton, PA, 

with Crayola Inc. The larger-than-life 

crayons falling 

from the roof of the 

Crayola Factory Visitors 

Center were cast in Poly 

15-6 Liquid Plastic. 

Poly 15 Series Liquid Plastics reproduce the finest detail. Fillers 

can be added to Poly 15 Series Liquid Plastics to create castings 

with varying looks and densities. 

Effect of 15X Addition on Pot-Life and Demold Times 

% 15X Pre- 

Mixed with B 

Pot-Life 

(1-lb Mass) 

Demold Time 

(¼-in casting) 

Shore D 

@ Demold 

Shore D 

@ 24 hr 


0.00 26 min 225 min 45-55 76 

0.10 8 min 16 min 38-55 76 

0.25 3 min 8 min 38-55 76 

0.50 1.75 min 6 min 38-55 76 

Note on Spraying Poly 1512X Plastic 

Poly 1512X accelerated with Poly 74/75 Part X can be sprayed 

using low cost spray equipment, such as Plas-Pak guns, or more 

sophisticated spray systems. The amount of 74/75 X required varies 

depending on temperature. Adding 1.35 g of 74/75 Part X to 1 lb of 

1512X Part B yields a 10 second working time sprayable plastic. 

Experiment to determine the amount of 74/75 X needed. Only spray 

in well ventilated areas such as a spray booth. For more information 

on Plas-Pak spray equipment, see p. 64. 

Mother Earth Float in Macy’s 74th Annual Thanksgiving Day 

Parade was hard-coated with Poly 1512X Liquid Plastic to create 

a tough, paintable surface. The float, sponsored by Maytag 

Neptune Washer, was built at Macy’s Parade Studio. 

15 Series Product 

Poly 15-3, 15-3X 


Poly 15-6, 1510, 1511, 1512, 1512X 


Poly 15-8 


Packaging 

Unit Sizes (lb) Part A (lb) Part B (lb) 

5.0 

20.0 

100 

4.0 

16.0 

80.0 

900 

3.2 

12.0 

48.5 

1 qt (2.5) 

1 gal (10) 

5 gal (50) 

1 qt (2.0) 

1 gal (8.0) 

5 gal (40.0) 

55 gal (450) 

1 pt (0.7) 

1 qt (2.5) 

1 gal (10.0) 

1 qt (2.5) 

1 gal (10) 

5 gal (50) 

1 qt (2.0) 

1 gal (8.0) 

5 gal (40.0) 

11 x 5 gal (450) 

55 gal (450) 1510 only! 

1 qt (2.5) 

1 gal (9.6) 

5 gal (38.0) 

50 

(610)559-8620 • (800)858-5990

Poly-Optic ® 

DESCRIPTION: Poly-Optic ® 14 Series Casting Resins are twocomponent, 

polyurethane systems that were formulated specifically 

for applications where optical clarity is a must. Use Poly-Optic 

plastics for casting decorative objects, production parts, models 

and more. Castings are clear like water; however, PolyColor dyes 

can be added to obtain clear, colored castings. Poly-Optic systems, 

with their low viscosities and long pot-lives, provide for easy mixing, 

excellent detail penetration and easy degassing resulting in 

bubble-free castings when vacuum or pressure casting techniques 

are employed. 

Poly-Optic ® 1410 cures to a hard plastic that is virtually 

unbreakable. Cure 1410 at room temperature and, for optimum 

physical properties, post cure at 150°F. 

Poly-Optic ® 1411 is an easy 1A:1B, by volume system that cures 

quickly to a super-strong, hard plastic. Poly-Optic 1411 develops 

hardness and can be demolded more quickly than 1410. It also has 

a higher heat deflection temperature, which is useful in certain 

prototyping applications. 

Poly-Optic ® 1420 cures to a tough, impact- and heat-resistant 

plastic that can be polished and machined. For strong plastic, heat 

cure 1420 at 150-180°F. For brittle, glass-like castings, cure at 

room temperature. 

Poly-Optic ® 14-70 is a firm rubber. Blend 1410 and 14-70 to 

achieve any hardness between Shore D85 and Shore A70. (See 

table on next page.) 

MOLD PREPARATION: Poly-Optic products reproduce minute 

detail from a mold or pattern but may stick or foam when poured 

on improperly prepared surfaces. A trial casting on a surface finish 

similar to the final mold should be made to avoid damaging a 

valuable mold. Polyethylene and silicone rubber molds, such as 

PlatSil ® 71and 73 Series products, do not require a release agent. 

[CAUTION: Condensation-cure silicones (i.e., TinSil ® 70 Series) 

are not recommended for casting Poly-Optic since residual alcohol 

may inhibit the cure or result in hazy castings.] Latex, 

polyurethane or metal molds must be dry and require a coat of a 

suitable release agent, such as Pol-Ease ® 2300 Release Agent. For 

optically clear castings, use highly polished masters to create 

molds with excellent surface quality. 


14 Series Clear Casting Resins 


FEATURES 

• Crystal clear, like water 

• Low viscosity for easy pouring 

• Reproduces fine detail 

• Can be machined, drilled and sanded 

• Long working time 

• Low shrinkage upon cure 

MIXING: See p. 46 for information on proper mixing. 

VACUUM DEGASSING OR PRESSURE CASTING: For 

bubble-free Poly-Optic castings, vacuum degassing or pressure 

casting must be employed. See page 16 for more information on 

vacuum and pressure. A light spray of Pol-Ease 2300 or quickly 

passing the flame of a torch over the back of the casting helps 

break any bubbles on the back of the pour. 

CURING: Poly-Optic 1410, 1411 and 14-70 cure at room temperature. 

For castings less than 0.25-inch thick, 1411 is recommended 

because it can be demolded more quickly in thin sections. 

For thinner castings, or when using Poly-Optic 1410 for thin parts, 

add Part 14X Catalyst or heat cure (8 hr at 140-150°F). Castings 

greater than 0.5-in thick do not require heat or 14X, but the addition 

or use of either will speed up the curing process considerably. 

Poly-Optic 1420 cures in 8 hours at 150°F, or 16 hours for optimum 

physical properties. If cured at a higher temperatures, parts 

may be demolded sooner (e.g., 30 min at 180°F depending on size. 

For brittle, glass-like parts, cure 1420 at room temperature. 

Wash mold release from surfaces prior to painting or bonding. 

ACCELERATING CURE SPEED: Mix Poly-Optic 14X 

Catalyst into Part B prior to adding Part A to accelerate the gel and 

cure time for Poly-Optic resins. 14X is recommended for castings 

less than 0.5-in thick. For best results, mix Parts A and B, degas if 

required, then add 14X and degas again if necessary. Adding 0.5% 

14X to the total mix weight speeds the cure significantly. For 

example, 0.5g 14X in a 100g mix of Poly-Optic 1410 halves the 

Poly-Optic ® Product 1410 1411 1420 14-70 

Mix Ratio 3A:2B, by weight 1A:1B, by volume 2A:1B, by weight 4A:5B, by weight 

Hardness (Shore A or D) D80 D80 D85 A70 

Pour time (min), 2-lb mix 15 9 15 15 

Maximum exotherm, 2-lb mass 265°F (129°C) 228°F (109°C) 311°F (155°C) 190°F (88°C) 

Demold time (hr)* 2 (1-in thick)* 0.5 (.5-in thick) 8 @150°F/0.5 @175°F 24-48 

Specific gravity 1.07 1.07 1.05 1.06 

Viscosity, 2 min after mixed (cP) 700 600 250 340 

Specific Volume, in 3 /lb 27.5 27.5 27.5 27.5 

* Demold time varies with thickness of casting and the amount of Part 14X Catalyst added. 



51



pour and cure time. Exotherm (heat of reaction; see p. 6) and thus 

shrinkage on cooling is also increased. Experiment to determine 

the best amount of 14X to use, but do not use more than 1% 14X 

because final physical properties may be affected. 

RETARDING CURE SPEED: Poly-Optic 14R Retarder slows 

the cure of Poly-Optic systems. Slowing the cure also reduces 

exothermic heating that can cause distortion, waviness and shrinkage 

especially in castings >0.5-inch thick. Add 1.5% 14R to the 

total mix weight of Poly-Optic 1410 to increase pot-life from 15 

minutes to 70 minutes. Add 1% 14R to 1411 to double the working 

time from 9 to 18 minutes. Depending on the size and mass of 

the part, post curing Poly-Optic 14-70 and 1410 parts in the mold 

at a minimum of 140°F for 12 to 16 hours may be necessary. The 

extended pot-life creates a lower exotherm upon curing, allowing 

larger castings to be made without distortion. Never use more than 

4% since the system may not cure properly. See table to right 

regarding 14R addition to 1410. 

COLORS: Add PolyColors (see p. 61) to 14 Series Part B before 

mixing with Part A to create clear plastics of any color. 

EXTERIOR USES: Although Poly-Optic 1410, 1411 and 1420 

are non-yellowing formulas, they are not recommended for longterm 

exterior use. Poly UV Additive can be added to improve 

durability for exterior applications. Add 1% UV Additive to the 

total mix weight of Poly-Optic to reduce the onset of chalking and 

pitting of the outside surface for ~2 years. Add 3% Poly UV 

Additive to achieve good exterior stability beyond 5 years. 



STORAGE LIFE: Poly-Optic liquids can be stored for at least 6 

months in unopened containers stored at room temperature. Poly- 

Optic Part As may crystallize slightly or become viscous during 

storage. If crystallization occurs warm the container to 100-120°F 

until crystals dissipate. Cool to room temperature before use. 

Product 

PACKAGING 

Unit Weight (lb) 

Poly-Optic ® 1410 10.0 

Mix Ratio 3A:2B 60.0 

Poly-Optic ® 1411 3.8 

Mix Ratio 1A:1B (By Volume) 15.2 

76.0 

Poly-Optic ® 1420 6.0 


120.0 

Poly-Optic ® 14-70 14.4 


Poly-Optic ® 1410 Gel Times with 14R Addition 

Weigh, add and mix 14R into 1410B. Weigh and add 1410A, 

plus one additional part A for every part of 14R used in the 

14R/1410B premix. Mix well. Pour into prepared mold. Degas 

or pressure cast for bubble-free castings. 

1410Part A 100 100.5 101 101.5 

1410Part B 66.6 66.6 66.6 66.6 

14R 0 0.5 1.0 1.5 

Gel Time 

(min) 

15 21 40 72 

Blending Poly-Optic ® 1410 and 14-70* for Various 

Hardnesses 

The clarity of Poly-Optic ® 

1410 is remarkable. This 

amazing negative sculpture 

comes to life with 

overhead lighting. 

1410 Part A 100 100 100 100 100 

1410 Part B 52 42 33 23 13 

14-70 Part B 25 44 62 82 100 

Shore A 

Hardness 

NA NA 95 88 75 

Poly-Optic ® 1410 Liquid 

Plastic was poured into 

a cylindrical mold to 

form a rod, which was 

softened in hot water 

and coiled around a 

mandrel. Once cooled, it 

holds its shape to form a 

tough, spring-like coil. 

Shore D 

Hardness 

87 77 60 37 25 

* Note: Premix Poly-Optic 1410 and 14-70 Part Bs prior to mixing 

with Part A. Poly-Optic 1410 and 14-70 Part As are the 

same; therefore, premixing Part As is not necessary. 

52 

(610)559-8620 • (800)858-5990


PolyFoam Series Casting Foams 

DESCRIPTION: PolyFoam Series Casting Foams consist of liquid 

Parts A and B that, after mixing, form self-skinning foams. 

PolyFoam can be used to cast rigid or flexible objects with densities 

in the range of 3-20 lb/ft 3 . Considered PolyFoam for production 

of decorative objects, lightweight mold shells, production 

parts, tools, models, patterns, fixtures, duplicate masters and general 

tooling use. PolyFoam systems do not contain toluene diisocyanate, 

MOCA, heavy metals or HCFCs, and are practically 

odorless. PolyFoam R-2, R-5 and R-8 are rigid foams. PolyFoam 

F-5 is flexible for casting soft parts. 

MOLD PREPARATION: See p. 46. Be sure that rubber molds 

used with PolyFoam are stiff enough so as not to distort when subjected 

to packing pressures. Use a suitable barrier coat such as 

Barrier PF to extend mold life when using rigid foams. If Barrier 

PF is used, apply Pol-Ease ® PF Release Agent to the mold prior to 

applying Barrier PF. 

MIXING: See p. 46 for general guidelines. Combine Parts A and 

B and mix immediately with a Turbo mixer or other high speed 

mixer for 30 seconds. Pour mix into cavity as quickly as possible 

since foaming starts immediately. If too much time elapses, the 

foam will rise in the mixing container and the mix may be lost. 

Once containers of Parts A and B are opened, they should be used 

or resealed tightly as atmospheric moisture contamination may 

degrade product integrity causing excess foaming, pressure build 

up and poor cure properties. To improve shelf stability of the liquid 

products, use Poly Purge to displace moist air in opened A and 

B containers before resealing. 

CURING: Packing PolyFoams to a minimum of 2-3 lb/ft 3 above 

their free-rise density is recommended to achieve good surface 

detail and mold fill. A lid with small vents to allow air to escape 

as foam rises should be firmly clamped in place prior to rise. Once 

foam begins rising, avoid stirring or other movement that will 

cause cells to collapse. Castings should be allowed to remain in 

the mold until thoroughly cured. Parts demolded too soon may be 

subject to deformation. For best casting results, the mold should 

be warmed to between 75°F and 85°F prior to casting the first part. 

Once a mold is heated and cycled, it will maintain heat for continued 

production. 

FINISHING: See p. 47 for general guidelines. When casting rigid 

foams, the use of an appropriate primer/barrier coat, such as 

FEATURES 

• Easy 1:1 mix ratios 

• Self-skinning foams 

• Rigid and flexible foams 

• Densities range from 3 to 20 lb/ft 3 

POLYFOAM PHYSICAL PROPERTIES 

Mix Ratio 

(By Weight or Volume) 

R-2 R-5/R-8 F-5 

1A:1B 1A:1B 1A:1B 

Mix Viscosity (cP) 500 1100 1400 

Cream Time (sec) 30 45 45 

Rise Time (min) 3 2 3-5 

Tack-Free Time (min) 10 3 25 

Demold Time (min) 30 10-15 30-60 

Free-Rise Density (lb/ft 3 ) 2.5 

5 (R-5) 

8 (R-8) 

5 

Molded Density (lb/ft 3 ) 4-8 8-20 8-15 

Note on PolyFoam Compaction Calculation: 

Using the desired density or compaction in pounds per 

cubic foot (lb/ft 3 ), divide that number by 1728 cubic inches 

(in 3 ). The result will be a decimal “factor” (0.004576 or similar). 

Then multiply the volume of the space you want to fill 

with foam (in in 3 ) by the “factor.” The result equals the 

pounds of PolyFoam liquid to prepare. 

Barrier PF, sprayed and allowed to dry in the mold before casting 

will result in a pre-primed part upon demolding. 



POLYFOAM PACKAGING 


Part A (lb) 

Components 

Part B (lb) 

PolyFoam R-2, R-5, R-8 and F-5 


(By Weight or Volume) 

4.0 

16.0 

80.0 

900 

1 qt (2.0) 

1 gal (8.0) 

5 gal (40.0) 

55 gal (450) 

1 qt (2.0) 

1 gal (8.0) 

5 gal (40.0) 

55 gal (450) 


53



Poly LiteCast Liquid Plastic 

DESCRIPTION: Poly LiteCast Liquid Plastic has a wood-like 

density and can be used to produce decorative objects, tools, models, 

patterns, fixtures and duplicate masters. Poly LiteCast reproduces 

fine details from molds and can be drilled, sanded and 

machined. 


MIXING AND CURING: See p. 46. [Note: Stir both Parts A and 

B before use since the filler in Poly LiteCast rises to the top.] 

ADDITIVES: To accelerate the cure, add Part 15X Catalyst. A 

few drops of Part 15X added to one-pound of mixed Parts A and 

B speeds the cure significantly. When using Part 15X, exotherm 

(heat of reaction) increases and can result in shrinkage of the cast 

part. Experiment to determine the right amount of Part 15X to use 

but never use more than 1% of the total weight of the mix or the 

final physical properties may be affected. 

If a paste-like consistency is needed for brush-on or trowel application, 

add Poly Fiber or Cab-O-Sil ® to thicken the mix. 

PolyColors (see p. 61) can be added LiteCast Part B before mixing 

with Part A to create plastic of any color. 



FEATURES 

• Wood-like density 

• Easy 1:1 mix ratio by weight or volume 

• Safe and easy to machine, contains no silica 

• Tough and hard, but not brittle 



1A:1B 

Hardness, Shore D 55 

Pour Time, 1 lb. mix (min) 5 

Demold Time (hr) (varies with 15X) 1 

Viscosity, 2 min after mix (cP) 2,480 

Specific Volume (in 3 /lb) 35 

Unit Weight 

PACKAGING 

Containers 


A B A B 

3 1 qt 1 qt 1.5 1.5 

12 1 gal 1 gal 6.0 6.0 

60 5 gal 5 gal 30.0 30.0 

Poly Plasti-Flex Liquid Plastic 

DESCRIPTION: Poly Plasti-Flex Liquid Plastic is flexible 

making it ideal for casting decorative trim and molding that needs 

to be mounted on a curved or uneven surface. Plasti-Flex can also 

be used to make special effects castings and props and impactresistant 

forms, tools and parts. Plasti-Flex has a wood-like density 

and can be drilled, sanded, nailed and screwed. 



ADDITIVES: PolyColors (see p. 61) can be added Poly Plasti- 

Flex Part B before mixing with Part A to create plastic of any color. 


PACKAGING 

Unit Weight 

Containers 


A B A B 

8.1 1 qt 1 gal 2.1 6.0 

38.5 1 gal 5 gal 10.0 28.5 

192.5 5 gal 5 x 5 gal 50.0 142.5 

FEATURES 

• FLEXIBLE! 

• Wood-like density 

• Safe and easy to machine, drill or sand (no silica) 



35A:100B 

Hardness, Shore A 90 

Pour Time, 1 lb. mix (min) 3 

Demold Time (min) ~15 

Viscosity, 2 min after mix (cP) 3,000 

Specific Volume(in 3 /lb) 34 

Poly Plasti-Flex architectural 

trim casting. The casting, 

which is held in a curved 

position, can be easily 

mounted on a curved surface. 

54 

(610)559-8620 • (800)858-5990

Polygel ® Liquid Plastics 

U.S. Patent # 5,128,433 


DESCRIPTION: Polygel ® Plastics produce strong, light-weight 

mold shells and are ideal for shells built up with a brush or spatula 

on vertical or overhead surfaces. Sprayable Polygel Shell is 

ideal for large surface area applications where brushing may be 

impractical. Polygel products consist of liquid Parts A and B, that 

after mixing 1:1 by weight or volume, immediately self-thicken. 

MIXING & CURING: See p. 46 for general guidelines. 

For Polygel Plastic-75, mixing of Parts A and B should be rapid 

and thorough. Most mixing should be completed within ten seconds 

or so before gelling begins and while the mix is still liquid 

to minimize air entrapment. Mix only enough that can be applied 

during the working time. Polygel Plastic-75 generates heat when 

mixed, so use rubberized cotton gloves to ease handling of the hot 

container. Once mixed, dumping the thickened mix on the surface 

to be coated and quickly spreading into a thin layer will cool the 

mass and extend working time by a minute or two. Do not try to 

demold Polygel Plastic-75 until adequate cure time has elapsed as 

it may be somewhat brittle. 

Polygel Shell Plastic is a rapid-setting liquid plastic designed for 

spray applications. Hand mixing is not recommended. When 

meter-mixed and sprayed 1:1 by volume, Polygel Shell gels several 

seconds after contacting the surface being covered, then 

remains in a workable grease-like state for 1 minute. Shells or 

castings can be demolded in 2 hours depending upon thickness 

and ambient temperature. Thicknesses ½-inch are not recommended as shrinkage can occur upon curing 

and cooling. For additional strength, lay fiberglass strand or 

mat while applying Polygel Shell. For very large shell sections, 

supporting structures such as boards or metal rods can be attached 

to prevent warping or damage during use. 

STORAGE: In order to maintain dimensions, Poly Plastic mold 

shells must be stored in temperatures


Polypoxy ® 

Resins 


DESCRIPTION: Polypoxy ® Resins and Poly Cure Hardeners are 

liquids that, after mixing in proper ratio, cure at room temperature 

to high-strength plastics. Resins can be cured with various curatives 

enabling users to select the best system for a particular use. 

The mix ratio for each curing agent and resin blend varies. For 

best results, carefully weigh the components. 

Polypoxy ® 1010 is a clear resin for use with fast Poly Cure 1212 

for small castings such as bonded bronze or with fiberglass or 

fillers for lay-up and mother molds. Use with Poly Cure 1220 for 

decoupage clear coatings, glass bonding and many other uses 

where a nearly colorless, clear, low viscosity resin is required. 

Polypoxy ® 1030 is an aluminum- and mineral-filled resin for 

lay-up or small castings when cured with Poly Cure 1212. For 

larger vacuum forming molds and other tooling uses, cure with 

Poly Cure 1230. Parts made with Polypoxy 1030 can be machined, 

drilled and burnished with steel wool to a pewter finish. 

SURFACE PREPARATION: Polypoxy Resins are adhesives 

and bond to many surfaces. If adhesion is not desired, surfaces 

must be made non-porous with a suitable sealer, such as wax, 

PVA, lacquer or other coatings. The surfaces must then be coated 

with a release agent such as Pol-Ease 2300. Poly 74 Series rubber 

molds require only a light, thorough coating of Pol-Ease 2300 for 

excellent release of epoxy castings. Perform a small test cure. 

MIXING: Polypoxy and Poly Cure must be mixed in the ratios 

shown below. Mix ratios are by weight except for Polypoxy 1010 

and Cure 1220, which can be mixed 1:1 by volume. Polypoxy and 

Cure must be thoroughly mixed and poured as soon as possible 

after mixing to ensure low viscosity and good flow. Watch a clock 

to avoid being caught with unused, cured material. 

HEAT RESISTANT CASTINGS: Polypoxy 1030 offers good 

heat resistance. Call Polytek for more information. 


SAFETY: Before use, read product labels and Material Safety 

Data Sheets. Follow safety precautions and directions. Poly Cure 

Hardeners cause severe eye and skin burns. Do not get in eyes or 

on skin. WARNING: The epoxy cure reaction is very exothermic 

(see p. 6). Do not cast large masses -- doing so can result in a fire! 

APPLICATIONS 

Polypoxy ® 1010 + Poly Cure 1212 

Bonded bronze 


Decoupage coatings and glass bonding 


Small castings and tooling applications 


Larger vacuum molds 

PACKAGING 

Product Unit Weight (lb) Container 

Polypoxy 1010 2.0 1 qt 

9.0 1 gal 

45.0 5 gal 

Polypoxy 1030 3.0 1 qt 

12.0 1 gal 

60.0 5 gal 

Poly Cure1212 0.25 4 oz 

2.0 1 qt 

Poly Cure 1220 0.25 4 oz 

2.0 1 qt 

8.0 1 gal 

40.0 6 gal 

Poly Cure 1230 0.25 4 oz 

2.0 1 qt 

8.0 1 gal 


Polypoxy + Poly Cure 1010 + 1212 1010 + 1220 1030 + 1212 1030 + 1230 

Parts Cure per 100 of Polypoxy 15 85 (1:1 by vol) 6 15 

Mixed Viscosity(cP) 3,000 3,000 10,000 5,000 

Pour Time, 150 g mix @ 77°F (min) 25 30 30 120 

Demold Time @ 77°F (hr) 4–8 48 24 24 

Maximum Casting Thickness (in) 0.5 1.5 3.0 8.0 

Shore D Hardness 95 80 98 95 

Specific Gravity 1.13 1.07 1.70 1.70 

Specific Volume (in 3 /lb) 24.5 26.0 16.3 16.3 

Density (lb/in 3 ) 0.0408 0.0386 0.0614 0.0614 

56 

(610)559-8620 • (800)858-5990

Speciality Materials 5 

Speciality Mold Making & Casting Materials 

This section describes a few speciality mold making and casting 

materials offered by Polytek. These materials can be used in 

conjunction with Polytek’s traditional mold rubber and casting 

plastic products, enabling users to tackle virtually any mold 

making and casting challenge. 

Latex - Tough, one-part brushable, castable rubbers 

Wax - Castable, carvable version; skin-safe version, 

acceptable for body molds 

Hydrogel - Safe for skin contact for body molds & life casting 

Poly Latex 60 

DESCRIPTION: Poly Latex 60 is a one-part, brush-on liquid 

that, after multiple coats, builds up to form a tough rubber blanket 

mold. Use Poly Latex 60 molds for casting plaster, concrete and 

limited casting with some resins. 

Poly Latex 60 has better tear strength than synthetic rubbers and 

is sometimes preferred for molds that are peeled off the casting 

like a sock. However, two-part, synthetic rubbers like Polygel ® 

products can be brushed on to final thickness in an afternoon and 

should be considered as a latex alternative (see p. 36). 

MODEL PREPARATION: The model should be free of oil, 

grease and dirt. Wood, oil-based clay, stone and glazed ceramics 

generally do not require any sealer. Plaster, unglazed ceramics, 

copper containing metals, water clay and cement should be sealed 

with shellac. Models made of other materials should be patch tested 

by applying a coat or two of latex to a small area. If the latex 

turns dark or sticks after drying, a sealer should be applied. 

Models with sharp edges or points may yield a better mold if the 

points are dulled slightly by sanding prior to sealing. Firmly 

mount the model on a suitable base board (i.e., plywood or a sink 

cutout available from kitchen counter shops). Drill a hole through 

the base board to allow air to escape from within the model so that 

trapped air does not cause defects in the mold. 

APPLYING & CURING: Brush a thin coat of latex on the 

model. Be careful not to puddle the latex. A gentle stream of air 

can help to blow latex into the finest detail and break any bubbles. 

Let each coat dry for 4 to 16 hours in a warm, ventilated room. 

Drying time depends on temperature and humidity. Warm, dry air 

is necessary for fast drying. When dry, the latex loses its milky 

appearance, and becomes slightly transparent and amber in color. 

Apply the next coat as soon as the first coat is dry. Apply 6 to 30 

coats depending on the desired mold thickness. Molds are typically 

1/16- to 1/8-inch thick. For large, flat models, apply latex in a 

checkerboard pattern, alternating squares between coats. Since 

there is some shrinkage on drying, the patchwork method reduces 

stress and warping of the latex as it dries. 

Latex can be thickened with ground cork, sawdust or Cab-O-Sil ® 

in order to fill undercuts. Thickeners must be completely wet out 

with latex and applied to the outside surface of the mold. The 

thickened latex must be allowed to dry completely as wet spots 

trapped in the latex can cause delamination of the mold. 

If needed, reinforce latex molds by placing fabric (e.g., muslin, 

burlap, polyester) into a coat of wet latex and then saturate with latex. 

Allow the fabric coat to dry completely before applying more latex. 

FEATURES 

• Brush-on liquid 

• Great for casting highly ornamental plaster and concrete 

• One part, no mixing or weighing needed 

• Tougher than any other mold rubber 

For spray application with a cup gun, mix 1 part Poly Latex 60 

with 1 part Poly Latex N. Poly Latex N is available in the same 

package sizes as Poly Latex 60. 

Before removing from the model, the latex must be thoroughly 

dry or heat cured. Heat in a warm oven at 110-150°F for 6 to 8 

hours to ensure a complete cure. If heat curing is not feasible, 

place the mold in a warm area for a week to strengthen the rubber. 

Clean up wet latex with soap and water. Dried latex can be softened 

with waterless hand cleaner and washed away. 

USING THE MOLD: Avoid exposing the mold to oils, grease or 

solvents. Molds can be washed with soap and water. Before casting 

plaster or cement, wet the mold with a 1% solution of detergent in 

water to aid air bubble release from the mold surface. Usually, no 

other release is necessary. For resin casting, a release agent such as 

Pol-Ease ® 2300 or PVA is needed. Most resins shorten the life of a 

latex mold -- Polygel ® or Poly-Sil ® rubber molds may last longer. 

SAFETY: Before use, read product label and Material Safety 

Data Sheet. WARNING! Latex products contain ammonia and 

causes eye and skin irritation. Avoid skin and eye contact. Use 

with adequate ventilation. In case of contact, flush eyes with plenty 

of water for 15 minutes and seek medical attention. Remove 

from skin and clothing with soap and water. 

STORAGE LIFE: At least 3 months in unopened containers 

stored at room temperature (50-70°F). Tightly reseal opened containers. 

As latex ages beyond 3 months, it will not cure to as supple 

a rubber and shrinkage on drying may increase and toughness 

of the mold will decrease. Exposure to temperatures below 40°F 

and above 80°F may damage latex, causing irreversible coagulation. 

DO NOT ALLOW TO FREEZE. 


PACKAGING 

Container 

2.0 1 qt 

8.0 1 gal 

40.0 5 gal 

400 55 gal 

Speciality 

Materials 


57

5 Speciality Materials 

Poly Latex False Face Compound 

DESCRIPTION: Poly Latex False Face Compound is a one-part 

pourable liquid that, when poured into a dry, unsealed gypsum 

mold, cures to a high-strength, flexible casting rubber. False Face 

was formulated to produce flexible hollow parts for uses such as 

novelty masks, flexible sculpture and animatronic applications. 

MODEL PREPARATION: To cure properly, this product must 

be cast into dry, unsealed, porous plaster molds. The user must 

determine the suitability of other porous mold materials. 

MIXING AND CURING: Shake or stir Latex False Face before 

use. Pour into a prepared gypsum mold. Tilting or lightly vibrating 

the mold may help eliminate bubbles if the mold contains 

complex undercuts or deep details. For a thin skin, pour the excess 

latex back into the container immediately. For a thicker skin, 

allow the latex to stay in the mold longer before pouring off 

excess. A standing time of 15 minutes yields a 3/32-inch thickness 

in a dry No. 1 Pottery Plaster mold. Denser plasters are not as 

Latex False Face molds can be made 

by dipping a dry, porous plaster model 

into False Face. The longer the model is 

submerged, the thicker the mold. This 

technique is only suitable for models 

with a shape that won’t trap air when 

placed upside down in the False Face 

liquid. 

FEATURES 

• Easy one-part rubber—no mixing or weighing 

• Tougher than any other mold rubber 

• Good reproduction of fine detail 

• Forms hollow castings without roto-molding 

absorbent and thicknesses build slower. Allow False Face to dry 

in the mold for 24 hours at room temperature. Elevated temperatures 

accelerate drying time. 

Clean up wet latex with soap and water. Dried latex can be softened 

with waterless hand cleaner and washed away. 

USING THE CASTING: Lightly dust the inside of the casting 

with talc in order to prevent the dry rubber from sticking to itself. 

Avoid exposing the casting to oils, greases or solvents. Castings 

should be stored out of direct sunlight. 

SAFETY & STORAGE: Same as Poly Latex 60 (see p. 57). 

PACKAGING 

Unit Weight 

Container 

2.0 1 qt 

8.0 1 gal 

40.0 5 gal 

Poly Wax 15 

Speciality 

Materials 

DESCRIPTION: Poly Wax 15 is a white, hard, low shrinkage, 

mineral-filled wax, which can be cast and carved. When cast, it 

replicates the mold surface in detail and finish. Tool cuts are 

smooth and lustrous. Dull surfaces can be hand polished with a 

soft cloth to a satin luster. 

MELTING AND CASTING: Poly Wax 15 softens below 130°F 

and is quite fluid at 160°F. Viscosity decreases rapidly as temperature 

is increased. At 200°F, components of the wax separate 

slightly. Mix the melted wax thoroughly before pouring. 

Complete mixing is quick and easy to determine visually -- mixed 

liquid wax is uniformly colored with no streaks. Use a nonporous, 

heat resistant stirrer such as a metal spatula. Pour temperatures 

are typically 210°F-280°F; however, the ideal temperature 

is dependent on the mold size, shape and material. Poly Wax 15 

holds temperature for a long time, so large or multiple molds can 

be filled in a single pour. When slush molding, excessively high 

temperatures will cause remelting of layers already laid down and 


Softening point 126°F 

Use temperature 210 - 280°F 

Viscosity @ 100°C (212°F) 116 cP 

Density (in 3 /lb) @ 25°C (77°F) 19.5 

@ 100°C (212°F) 21.6 

FEATURES 

• Ideal for prototypes 

• Cast carving blanks from rubber molds of rough originals 

• Suitable for master models 

• Smooth and lustrous surfaces 

significantly prolong the procedure. Casting temperatures that are 

too low will result in surface bubbles and “knit” marks because 

the wax solidifies too rapidly on the mold surface. 

Poly Wax 15 can be poured in Poly 74 Series, Poly-Fast 72-40, 

Poly-Sil ® , Polygel ® or Hydrogel ® molds. Latex will be softened 

by continual pours of Poly Wax 15. Most heat resistant resins and 

metal molds are also suitable; however, a small trial casting is 

always recommended to be sure castings release satisfactorily 

and do not damage the mold material. 


Safety Sheets. Hot wax can cause severe burns and ignites easily. 

Avoid skin contact. Do not heat with an open flame. Do not heat 

above 280°F since vapors can ignite. 

STORAGE LIFE: At least 12 months from date of shipment. 

PACKAGING 

Poly Wax 15 is available in 5-lb blocks 

58 

(610)559-8620 • (800)858-5990

Poly Skin-Wax 

Speciality Materials 5 

DESCRIPTION: Poly Skin-Wax is a liquid at temperatures as 

low as 125°F and it is somewhat elastic after solidifying. It can be 

applied to models using dip or brush-on techniques. Poly Skin- 

Wax has been formulated with non-toxic materials and is safe for 

skin contact provided temperature is carefully controlled. 

MODEL PREPARATION: When making a mold of a body part, 

coat skin and hair with baby oil before applying Skin-Wax. Molds 

can only be made of body parts that are covered with short and 

light hair -- do NOT attempt to make molds from hairy areas. For 

most other non-porous models, Poly Skin-Wax is self releasing 

and, therefore, no release agent is needed. Make a small test mold 

on a surface identical to the model to determine that release properties 

and hardening of Skin-Wax is suitable. 

PROCEDURE: Use a therapeutic paraffin bath, available from 

medical supply stores, to melt Poly Skin-Wax. A crock pot can be 

used to melt Skin-Wax; however, extreme caution must be exercised 

to ensure that the wax is not overheated. To melt Poly Skin- 

Wax, heat to 160-180°F. Skin-Wax must be cooled to 125-135°F 

before contact with skin! Even this temperature may cause discomfort 

in some individuals. Do not use Skin-Wax on sensitive 

areas such as the face. The wax must be just hot enough to produce 

good results; a few degrees hotter can cause considerable 

discomfort. Test judiciously on small areas. 

Stir Skin-Wax often during melting and use since temperature 

variations in an unstirred bath can result in solidified wax in one 

area of the bath while another area heats enough to cause burns. 

Monitor temperature in several places in the bath (i.e., near walls, 

center and at several depths). Use an accurate thermometer. 

Apply Skin-Wax by dipping the model, brushing on or slowly 

pouring over the model surface. For rapid cooling, immerse the 

wax-coated model in cool water between coats. Skin-Wax can be 

reinforced by laying fabric such as cheese cloth onto the previous 

coat and then applying wax to saturate the fabric. 

Although some flexibility remains in Poly Skin-Wax at room temperature, 

if flexibility is needed to remove the model, it is best to 

remove it as soon as the wax cools into the elastic (temporarily 

deformable) state. For model shapes that do not allow removal 

with the mold intact, the mold may be carefully cut and later 

rejoined using a warm metal spatula or by “welding” with molten 

wax. Small air vents punctured in the mold using a pin or wire 

may help release the mold from the model; for example, in casting 

a hand, pinholes at the end of each finger facilitate removal of 

the hand. Holes can be sealed later with a dab of molten wax. 


Softening Temperature 125°F 

Use Temperature 

125-180°F 

Viscosity @ 180°F 

190 cP 

Specific Volume (in 3 /lb) @ 77°F 31 

@ 180°F 34 

FEATURES 

• Safe for skin contact 

• One-part mold making compound 

• No mixing -- simply melt and use 

• Fast -- make a mold in 5 to 10 minutes 

• Easily repaired with a dab of warm wax 

• Flexible when warm 

• Self releasing from most surfaces 

• Reusable 


Safety Sheets. Follow safety precautions and directions. Do not 

heat with open flame. Do not heat above 280°F since vapors can 

ignite. Use with adequate ventilation. Do not use in the presence 

of sparks or open flame. Exercise extreme caution when applying 

Poly Skin-Wax to the skin. While Poly Skin-Wax is safe for skin 

contact, it is not recommended that repeated castings be made 

over a short period as the hot wax tends to remove skin oils and 

can cause irritation. For skin applications, avoid reusing wax that 

may have absorbed irritating substances from casting materials. 

STORAGE LIFE: At least 12 months from date of shipment. 

PACKAGING 

Poly Skin-Wax is available in 5-lb blocks 

The hand is dipped into melted Poly 

Skin-Wax (125°F) then into cold water to 

harden the wax. Over the next few minutes 

the process is repeated 2 or 3 

times to buildup mold thickness. After 

the wax is hardened, the mold is slipped 

off the hand and is ready for casting. 

Plaster, cement, rubber or plastic can be 

poured into the hand mold. Be careful 

not to use a casting material that generates 

significant heat upon cure. The wax is removed from the 

casting and can be melted for reuse. That casting is detailed -- 

fingerprints and all! 

Speciality 

Materials 


59

5 Speciality Materials 

Hydrogel ® 

N Mold Compound 

Speciality 

Materials 

DESCRIPTION: Hydrogel ® N is a white powder that after mixing 

with water cures in about 5 minutes to a moist, rubbery material. 

Use Hydrogel N to make quick, single-use molds, especially 

when skin contact is required. Plaster, wax, and certain EasyFlo 

Plastics can be cast into Hydrogel N molds. 

MODEL PREPARATION: Hydrogel N can be poured on most 

surfaces with minimal preparation, but perform a small test cure 

to be sure that Hydrogel N releases cleanly and does not damage 

water sensitive surfaces. Use a thin coat of petroleum jelly or Pol- 

Ease ® 2300 Release Agent to seal questionable surfaces. 

MIXING AND CURING: Weigh or measure proper amounts of 

Hydrogel N powder and room temperature water. The mix ratio is 

3 parts water to 1 part Hydrogel N, by weight, or approximately 1 

water to 1¼ Hydrogel N, by volume. Mix together rapidly to a 

creamy consistency, but avoid whipping in air. For best results, 

use a Turbo Mixer (see p. 62) on a variable speed drill. Add powder 

or water as needed to thicken or thin the mix. Working time is 

about 5 minutes, but can be extended using Retarder Solution (see 

table below). Apply the creamy mix to the model surface with a 

flowing motion, pushing air ahead of the mix. Demold with care 

2 to 3 minutes after the mix has gelled. 

To make a large blanket mold, make and apply a series of mixes 

within 5 minutes of one another. Hydrogel N bonds to itself if the 

previous mix is not completely gelled. To help a new mix bond to 

already gelled Hydrogel N, wipe the gelled material with a saturated 

solution of water and baking soda (sodium bicarbonate). 

Add food color to the bonding solution so that you know where it 

has been applied. Continue layering Hydrogel N as needed to 

make a ~3/8-inch-thick blanket mold. In the final layer of wet 

Hydrogel N, press “teased” cotton (cotton rolls, available at any 

pharmacy) evenly over the entire mold surface and allow to gel. 

Remove excess cotton by pulling gently, leaving a thin layer of 

exposed fibers. As soon as Hydrogel N is firm, mix and apply a 

plaster mold shell using bandages, cheesecloth, or hemp embedded 

in the plaster. The exposed cotton fibers in the mold will bond 

to the plaster shell helping to keep the mold attached. When the 

FEATURES 

• Non-toxic-- Safe for body casts 

• Easy to use: just add water and mix 

• Good reproduction of fine detail 

• Early strength for fast demold 

• Variable working time 

• Low cost 

Hands up and on 

the table! With the 

use of Hydrogel ® N, 

these children each 

made a plaster cast 

of their own hand at 

a Vacation Bible 

School craft session. 

Molds for 35 

hands were made in 

less than 2 hours! 

plaster shell is set, remove the Hydrogel N mold/plaster shell. For 

best dimensional stability, make a positive casting immediately. 

USING THE MOLD: Plaster or waxes below 212°F may be 

poured in Hydrogel N molds. For best results use the mold when 

it is as fresh as possible, since Hydrogel N molds shrink as they 

dry. Molds can be kept useable in plastic bags or sealed containers 

for up to a few days. Molds should then be discarded 

SAFETY: Before use, read product label and Material Safety 

Data Sheet. Follow safety precautions and directions. Handle 

Hydrogel N carefully to avoid dust generation. Wear a dust mask. 

Avoid eye contact. Hydrogel N is not for human consumption or 

use against mucous membranes. Keep skin contact as brief as possible. 

Prior to placing Hydrogel N on hair, hair should be slicked 

down with petroleum jelly or cholesterol hair conditioning cream. 

STORAGE LIFE: At least six months in unopened containers. 

LIQUID RETARDER (OPTIONAL) 

% Retarder Approximate 

in Water 

Working Time 

0 5 min 

3 7 min 

6 8 min 

9 10 min 

PACKAGING 

Hiram Ball, of Ball Consulting Ltd., demonstrates making a livebody 

mold using Hydrogel ® N. The safe-for-skin-contact alginate 

yields excellent mold impressions if wax or plaster is cast right 

after demolding. 

Product 

Hydrogel ® N 

Retarder Solution 

Volume 

1 qt 

1 gal 

5 gal 

1 qt 

60 

(610)559-8620 • (800)858-5990

Accessories 6 

MATERIALS 

RELEASE AGENTS 

HEMP - Long, natural 

fiber that has been the 

traditional reinforcement 

for plaster mother molds. 

Available in convenient 

10-lb bundles or 

economical ~40-lb bales. 

POLY FIBER II - Add to 

liquid rubbers to thicken 

for brush-on application 

or plastics for mold 

shells or layup castings. 

Add to resin (up to 5% 

total weight) to produce 

thin gels to thick pastes. 

(5-gal pail or 10 lb bag) 

TIETEX ® FABRIC - 

Strong, conformable 

reinforcing fabric that 

wets out very well. 

Small pieces can be 

laminated in at the top 

of a seam in brushed or 

sprayed molds to 

prevent tearing. A sheet 

can be laid into the back of an open poured 

mold to increase durability. Use as bridging 

material for spanning undercuts in sprayed or 

brushed molds. 

10-ft sheet (40-in wide) 

324-ft roll (40-in wide) 

FIBERGLASS MAT - Non-woven, 1.5 oz per sq. 

ft., chopped strand mat for reinforcing Polytek 

resins. 3 square yards 

POLYPLASTICENE - Non-hardening, sulfur-free 

modeling clay. Non-toxic and odorless, with a 

smooth, firm consistency for sculpting. Also 

makes great reusable caulk for mold boxes. 

1-lb block or 50-lb box. 

FUMED SILICA/CAB-O-SIL ® - Add to mixed 

liquid rubbers and plastics to make thicker and 

thixotropic mixes for brush-on application. 

5-gal pail 

10-lb bag 

Cab-O-Sil is a registered trademark of the Cabot 

Corp., Tuscola, IL 

BRONZE POWDER - Use with unfilled resins 

for "cold-cast bronze." One part bronze 

powder to one part EasyFlo (by volume) 

makes beautiful castings! 

2-lb can 

10-lb can 

110-lb can 

POL-EASE ® MOLD RINSE - Liquid concentrate 

reduces surface air bubbles on plaster castings 

made in Polytek rubber molds. Dip or spray 

mold with 1 part Pol-Ease Mold Rinse diluted 

with 10 parts water. Molds should be wet 

when plaster is poured. 5 gal (40 lb) 

POL-EASE ® MOLD DRESSING - Protects and 

rejuvenates Poly Rubber molds that have been 

exposed to harsh conditions created by the use 

of solvents and petroleum oils contained in 

certain form releases and casting resins. 5 gal 

(40 lb) or 55 gal (450 lb). 

POLYCOLORS - NEW! Dyes for coloring 

Polytek’s polyurethane 

rubbers and plastics. 

Available in red, blue, 

green, yellow, brown and 

black. 0.25-lb bottle or 1.0-lb bottle. 

UV ADDITIVE - For Improved Exterior 

Exposure - Thoroughly stir this liquid additive 

into polyurethane liquid rubber to improve 

exterior durability; greatly reducing 

characteristic surface degradation caused by 

sunlight or other UV light sources. Add 0.5% 

of the total weight of liquid mix prior to curing. 

4-oz bottle or 1-pint bottle (1 lb). 

POTTERS SOAP - Use to seal plaster models. 

Plaster should be damp when soaped. 

Available as a concentrate from Crystal Inc, 

Philadelphia, PA, (215) 368-1661. 

ADHESIVES 

POLYPOXY ® QUICK STICK 

ADHESIVE - Two-part epoxy 

adhesive with a 1:1 mix ratio 

by weight or volume. Bonds 

quickly to most clean, dry 

surfaces. Sets in 3-5 minutes. 

2-lb kit 

POLYBOND - A polyurethane adhesive that’s 

great for repairing torn molds. PolyBond has 

1A:3B mix ratio (by weight), a ~3 minute 

working time and a ~15 minute cure. 

2-lb kit 

EPOXYBOND - A low viscosity, epoxy 

adhesive, which deeply penetrates porous 

surfaces creating an excellent bond. It has an 

easy 1A:1B mix ratio (by volume), a long 

working time (120 min.), and overnight cure. 

2-lb kit 

POL-EASE ® 2300 RELEASE 

AGENT - A blend of silicone oils 

and resins in a convenient aerosol 

spray. Pol-Ease ® 2300 is an 

effective release for use with most 

Polytek products. Use a soft brush 

to distribute evenly. 

12-oz can or Case of 12 cans 

POL-EASE ® 2500 RELEASE 

AGENT - An aerosol spray release 

agent that can be easily washed 

off cast parts for easy finishing. 

Spray a thin mist over mold 

surface, then brush gently for 

uniform coverage. 

12-oz can or Case of 12 cans 

POL-EASE ® 2350 RELEASE AGENT - Mineral 

spirits solution for use with RTV liquid silicone 

rubbers. Can be brushed or sprayed. Use of a 

soft brush to spread the release agent evenly to 

improve results. 1 qt (1.5 lb) or 5 gal (26 lb) 

POL-EASE ® 2450 RELEASE AGENT - A fast drying, 

silicone-based release, which can be brushed or 

sprayed. Flammable! 1 qt (1.5 lb) or 5 gal (30 lb) 

POL-EASE ® 2601 RELEASE AGENT - Water-based 

emulsion of silicone oils and resins. Spray 

with the Sure Shot Mini Atomizer for an 

economical alternative to aerosol release 

agents. After spraying, distribute evenly with a 

soft brush. 1 qt, 5 gal (40 lb) or 55 gal (450 lb) 

POL-EASE ® 2650 RELEASE AGENT - A high 

performance, silicone-free, release agent for use 

in polyurethane molds when casting concrete or 

plaster. 1 qt (1.5 lb) or 5 gal (35 lb) 

POLY PVA SOLUTION - Water soluble coating 

for use as a barrier coat on certain rubber 

molds (i.e, Poly-Fast 72-40) to allow resins to 

cure without sticky surfaces. While Poly 74, 

70 and 71 Series molds do not cause sticky 

surfaces on resin castings, PVA may be used 

as a barrier coat to prevent resin attack on the 

mold. Can be used as a removable sealer for 

porous surfaces alone or in conjunction with 

paste wax. The green film of PVA washes off 

with water. (Specify Clear or Green) 1 qt (2.0 

lb) or 5 gal (35 lb) 

POLYCOAT - A semi-permanent sealer and 

release agent that can be sprayed or brushed 

onto a model when using liquid polyurethanes. 

In most cases no additional release is needed to 

demold the polyurethane rubber. 1 qt or 1 gal 

SURE SHOT MINI ATOMIZER -Use with Pol- 

Ease ® 2601, 2350 and 2450 Release Agents. 

Mini Atomizer (7-oz capacity) 

Accessories 


61

6 Accessories 

MIXING EQUIPMENT 

BRUSHES 

SAFETY 

Accessories 

POLY PADDLE - 

The 16-inch 

Poly Paddle 

allows complete 

mixing of material by thoroughly scraping the 

sides and bottom of rounded or straight sided 

mixing containers. 

SPATULAS - 

Top quality, all 

purpose spatula 

with a 

comfortable, 

cushion-grip, 

vinyl handle is unbreakable, and heat and 

chemical resistant. The stainless steel blade is 

semi-flexible for durability and easy mixing. 

The mirror finish wipes clean easily. Available 

in two sizes for most small mixing needs. 

4-in Blade Spatula 

6-in Blade Spatula 

JIFFY MIXERS - 

Heavy-duty, 

efficient, 

commercial 

mixer, specially 

designed for 

tough-to-mix, viscous materials. Mixes 

quickly and thoroughly without splashing or 

whipping air into the mix. The patented 

protective-ring design prevents puncture or 

damage to the mixing container. Made entirely 

of stainless steel 304 for maximum durability. 

Jiffy mixers fit all ¼- to ¾-inch chucked 

power tools. Tools with 450-700 rpm give the 

best mixing results. 

Jiffy Mixer, 1 gal 

Jiffy Mixer, 5 gal 

TURBO MIXERS - 

Ingenious, 

patented, high 

efficiency 

mixers fit any 

power drill with 

½-inch chuck and mix more efficiently than a 

Jiffy Mixer. Must be kept free of built up 

material. It’s worth the price! 

Turbo Mixer, ½-gal 

Turbo Mixer, 1-2 gal 



TONGUE DEPRESSORS - Made 

of straight-grained white birch 

for consistent quality. 

Convenient, low cost mixing 

tools for test cures or small 

quantity mixes. 

6-in length, box of 500 

ACID BRUSHES - Tinhandle, 

disposable ½-inch 

wide brushes with 100% 

horsehair bristles. 

Excellent for making small 

brush-on molds. Bundle of 

30 or Box of 1 gross (144) 

CHINA BRISTLE BRUSHES 

- Wooden handle chip 

brushes. 100% China 

Bristle available in 1- 

inch and 2- inch width. 

Use to apply brush-on 

molds or release agent. 1-in Brush, bundle of 

10; or 2-in Brush, bundle of 10 

MOLD BOX 

MOLD BOX - 

Adjustable to any 

size up to 24-in x 

24-in x 6-in. The 

base is smooth, 

plastic faced 

particle board. This mold box provides a quick 

way to pour a rubber mold. (C-clamps not 

included.) 

MOLD-KEY KNIFE 

mold registration easy. 

MOLD-KEY KNIFE 

- NEW! Use this 

unique notched 

knife to cut 

tongue-and-groove 

seams in molds. 

Makes proper 

BANDS & STRAPS 

RUBBER BANDS - Top 

quality ¾-inch wide 

rubber bands made of 

long lasting, heavy duty 

natural rubber. Secures 

mold shell pieces 

firmly together. 4-in 

Bands, 1-lb box 8-in Bands, 1-lb box 

NYLON MESH MOLD 

STRAPS - One-inch wide 

nylon straps are 

adjustable to 8 ft in 

length. They tighten as 

the buckle locks to 

ensure a snug fit. Sold singly or bag of 12 

NITRILE GLOVES - 

Disposable, powder-free, 4- 

mil nitrile gloves offer 

comfort, dexterity and a 

broad range of chemical 

resistance. These gloves 

offer protection against intermittent contact 

with nearly all Polytek products. Contain no 

natural rubber proteins. 100 per box, Size L 

SAFETY GLASSES - With a 

sleek wrap-around 

polycarbonate lens, Uvex 

Bandido ® safety glass 

offers excellent eye protection, comfort and 

sporty styling. Meets ANSI Z87.1-1989 

Standard. Made in USA. 1 pair (one size) 

PROTECTIVE COVERALL - 

Kappler NexGen coveralls 

are made of a micro-porous 

fabric that is aerosol and 

liquid proof. Disposable, 

but durable enough to be 

reworn. Large size and 

light weight allows 

mobility. The perfect 

cover-up for quick, dirty 

jobs. Coverall, Size L 

SOLVENT DISPENSING CAN 

- Plunger can for 

dispensing flammable 

liquid features brass flame 

arrestor screens and pump 

assembly. Simply press a 

cloth or wiper on the 

plunger to moisten. Two-quart capacity. 

Although we don’t offer a full line of 

safety supplies, we’ll help you get what 

you need to work safely! Call Polytek and 

ask for our safety specialist. 

PAILS/OPENER 

PAILS FOR MIXING - High density 

polyethylene pails with handles, both 1-gal 

and 5-gal sizes are now available in cartons. 

These are the same pails that Polytek uses for 

its products. They are excellent for mixing 

Parts A & B and often the cured residue can be 

stripped out, leaving a clean pail ready for 

reuse. Lids can be ordered separately. 

1-gal Pails (Box of 10) 

5-gal Pails (Box of 5) 

PAIL OPENER - “Pail Pal” pail opener designed 

to open and close most plastic pails with ease. 

Constructed of rugged cast aluminum. 

62 

(610)559-8620 • (800)858-5990

Accessories 6 

SCALES 

DVDS/VIDEOS 

BOOKS 

OHAUS CS-2000 PORTABLE SCALE - The ideal 

scale for users who need a 

scale in a variety of 

locations during the work 

day. Battery operated with 

an automatic shut-off 

switch. The CS-2000 has a 

capacity of 2000 grams (~5 

lb) and readability to 1 

gram. The digital display reads in grams or 

pounds and ounces. The scale offers simple 

operation with a full capacity tare. The CS- 

2000 has an easy-to-clean weighing surface. 

The AC adapter is sold separately. 

OHAUS ES50R ELECTRONIC BENCH SCALE - 

This all-purpose, 

rugged bench scale 

is equipped with a 

large, stainless steel 

weighing pan to 

withstand heavy 

industrial use. The 

ES50R has a 110-lb capacity, a digital display 

readable to 0.05 lb and a full capacity tare. 

Can be used with the AC adapter (included) or 

batteries for portability. An automatic shut-off 

circuit extends battery life. 

OHAUS 760-00 TRIPLE-BEAM BALANCE - 

Quality, mechanical 

balance 

with readability 

to 0.1 gram and 

weighing 

capacity to 2610 

grams (5+ lb) makes this balance more than 

adequate for weighing small quantities. 

Weight set included. 

OTHER ACCESSORIES 

POLY PURGE DRY GAS 

BLANKET - Blast Poly 

Purge into an open 

container just before 

resealing the lid to displace 

moist air and extend the life 

of polyurethane liquids. Poly 

Purge is heavier than air 

and is non-flammable and 

non-ozone depleting. It is packaged in an 

aerosol can with a special nozzle extension 

useful for directing the gas into the desired 

space. 10-oz can or Case of 12 cans 

Polytek offers DVDs and video tapes to help 

customers better understand mold making 

materials and processes. 

POLYTEK MOLDMAKING DVD 

Watch step-by-step demonstrations showing 

how to make a 

poured block mold; 

brushed blanket mold 

with plastic shell; 

and a poured blanket 

mold with a plastic 

shell. See how to use 

Polytek polyurethane 

and silicone rubbers 

and plastics. Only 

$5.95! 

POLYTEK BODY CASTING AND SPECIAL 

EFFECTS SEMINAR/WORKSHOP 

Body & Face Casting with Hydrogel ® 

Alginate, 115 min. 

BALL CONSULTING LTD. 

MOLD MAKING AND CASTING 

A practical how-to video showing the making 

of a poured mold, a brush-on mold and a 

poured blanket mold. Casting of Forton ® MG 

with a metal powder filled face mix and a 

glass fiber reinforce back-up. Covers patinas 

and other finishing techniques. Use of Forton ® 

MG to spray-up a large, rigid column mold 

and rigid carrier molds also shown. Approx. 

40-min. 

SUCCESS WITH FULL BODY MOLDS AND 

FORTON ® CASTINGS 

The definitive video on full-body molding. 

This Mark Prent video also includes useful 

information on casting with Forton ® MG. 

Approx. 70 min. 

BETTER ONE-PIECE HEAD MOLDS FROM LIFE 

Master sculptor Mark Prent takes you step-bystep 

through every detail of using alginate 

mold compounds to make head molds of live 

models (i.e., Hydrogel ® N). Approx. 75 min. 

THE USER’S GUIDE TO REDUCIT ® 

RUBBER MOLDS, AND INNOVATIVE PLASTIC 

SUPPORT STRUCTURES 

Mark Prent uses Polytek Mold Rubbers and 

alginate compounds to reduce a life size 

sculpture to ¼-scale in two steps. This video 

offers the solution to an age old problem while 

maintaining every detail of the original. 

Approx. 60 min. 

METHODS FOR 

MODERN SCULPTORS 

By Ronald D. Young 

& Robert A. Fennell 

Published in 1980, this 

is still one of the best 

general texts on the 

subject, including a 

very good chapter on 

mold making. (292 pp) 

POLYTEK CURED SAMPLE STRIPS 

Two pages of cured sample strips of most 

Polytek rubbers and resins in a 3-ring binder. 

A handy reference when selecting a material 

for a particular job. 

ROTATIONAL CASTING 

Rotational casting involves rotating a closed 

mold while a liquid casting material flows over 

the inner surface of the mold. The liquid clings 

to the mold surface just enough to create a thin 

layer of cured material, which creates a hollow 

casting. Rotational casting is an efficient 

method of creating large, lightweight pieces 

such as mannequins and figurines. Fast-setting 

liquids are used so that pieces can be produced 

with short cycle times. 

The 2 machines pictured below are at our PA 

facility and are available for demos and test runs. 

Small machines cost 

~$5,000 and can support 

mold loads of ~ 200 lb. 

Table-top versions are 

available. Large 

machines can carry 

many molds and cost ~ 

$12,000. 

Accessories 


63

6 Accessories 

DRUM HANDLING PRODUCTS 

POLYGEL ® SPRAYER 

Polytek offers numerous products to make 

handling drums easier and safer. A few items 

are shown below. Call Polytek for pricing and 

details. 

Oil-Gate Valve 

for 2-inch Bung 

Drum Bung 

Wrench, 

Standard Bronze 

Drum Deheader 

Drierite 

Cartridge 

Meters, mixes and sprays select Polygel ® 

rubbers and plastics. Makes superior quality 

molds and shells much faster than hand 

application using self thickening Polygel ® 

rubbers and plastics. 

METER MIX EQUIPMENT 

Accessories 

Drum Cradle 

Drum Hand 

Truck 

Hand Truck 

DRYING CARTRIDGE PROTECTS PRODUCT 

INTEGRITY - Drums of Polyurethane products 

(both Parts A & B) benefit from use of Drierite 

Dessicant Cartridges. The cartridge is screwed 

into the small bung with an adapter so that air 

entering the drum during dispensing is dry. 

Protects product integrity. Drierite Cartridges 

have a window to view color change to 

determine when cartridge is spent. 

Drierite Cartridge and Adapter sold separately. 

Poly 74-55 drum 

unit ready for 

use with valve, 

cradle and 

Drierite 

cartridge. 

Meter mix and dispensing equipment 

automatically measures, mixes, pumps or 

sprays Polytek liquid rubbers and plastics. For 

recommendations on this type of equipment, 

call Polytek Customer Service at 800-858-5990. 

PORTABLE SPRAY SYSTEMS 

Certain Polytek polyurethane and silicone 

liquid mold rubbers and plastics ( e.g., 

Polygel ® 

rubbers & plastics, accelerated 

1512X polyurethane plastic & TinSil ® 

Spray 

25) can be inexpensively meter mixed and 

sprayed using sprayer assemblies and 

accessories from Plas-Pak Industries. Two gun 

assemblies are available - a 1:1 mix system for 

polyurethane rubbers and plastics and a 1:10 

sprayer for TinSil ® 

Spray 25. Both sprayers 

are available from Polytek and come equipped 

with a pressure regulator kit and a 

Mixer/Spray Gun Assembly. You need to 

supply the air compressor. Empty cartridge 

assemblies (one tube for Part A and one for 

Part B are molded into one piece for 

convenience) and static mixers are sold 

separately. Cartridge assemblies may be 

reused when handled carefully or disposed if 

cleanup is impractical. Static mixers are 

disposable and should not be reused. 

Pallet Truck 

With this handy spray system you can 

complete a mold in a one-application session. 

For larger volume applications, Polytek 

products can be purchased in totes. Polytek also 

offers accessories for handling and dispensing 

products from totes. Call Polytek for details. 

For recommendations on this type of 

equipment, call Polytek Customer Service at 

800-858-5990. 

64 

(610)559-8620 • (800)858-5990

Accessories 6 

TRIAL UNIT ORDER POLICY 

GLOSSARY 

See for yourself! Try Our Introductory Offer. 

To encourage you to evaluate our products, Polytek will ship you the trial unit(s) 

freight paid (except for hazardous material fees, if any) in the contiguous 48 

States at special low prices. Only one trial unit shipment of each product per 

customer. Subsequent orders are at list price. Directions and MSDSs are sent with 

trial units. All trial unit orders must be prepaid. 

Freight is free for accessories shipped with a trial unit, up to the value of the trial 

unit. Call for details. 

TRY YOUR LOCAL DISTRIBUTOR FIRST 

Polytek has stocking distributors worldwide; more every day. Call Polytek to learn 

the name and location of the distributor in your area. 

NOTES & POLICIES 

Prices are per unit, including both A & B. (Except one-part materials and certain epoxies.) 

Terms are 1% 10 days, net 30 days for accounts with approved credit. 

Orders prepaid with credit card, money order or wire transfer will usually be shipped 

the next day providing items are in stock. 

Orders prepaid with check are subject to delayed shipment until the check clears. 

No COD Shipments. 

Prices do not include state and local taxes. 

State tax exemption certificate required for PA customers. 

Prices are subject to change without notice. 

Prices are FOB Easton, PA. 

Freight will be prepaid on shipments valued over $4,000 for delivery in the contiguous 

48 States. 

Minimum order $40; also applies to trial units. 

Any single pint size bottle of Silicone Part A is the full 1-lb kit price for that product. 

Any ½-gal size bottle of Silicone Part A is the full gallon-size kit price for that product. 

Minimum charge for any small container is $5. 

All video and book sales are final. No returns or refunds. 

Returns must be pre-approved and a 20% stocking charge is charged on all returns. 

Return Check charge is $25. 

TRADEMARKS 

Polytek ® , Polygel ® , Polypoxy ® , Poly-Optic ® , Poly-Sil ® , FormRub ® , Hydrogel ® , 

PlatSil ® , TinSil ® and Pol-Ease ® are registered trademarks of Polytek Development 

Corp., Easton, PA 18042 USA. Registration is pending for EasyFlo, PolyFoam, Poly 

LiteCast, EpoxyBond, Poly Purge and PolyBond. 

Cab-O-Sil ® , Tietex ® and Forton ® are marks of their respective manufacturers. 

Blanket Mold: A thin blanket-like rubber 

mold, usually ¼- to ½-inch thick. A rigid 

shell (mother mold) is required to hold 

the floppy blanket mold in perfect shape. 

Chasing: The process of cleaning 

unwanted material (flashing) from a 

casting. 

Flashing: 1. Unwanted fin-like 

projections of casting materials that have 

flowed into mold vents and parting lines. 

2. Thin aluminum sheet used to divide 

mold sections. 

Inhibition: Failure of a compound to 

cure against a surface within the 

recommended cure time. The surface in 

contact with the pattern remains gummy 

or uncured. Inhibition is most likely to 

occur in addition-cure (PlatSil ® ) silicone 

systems. 

Keys: Tongue-and-groove, or button-like 

impressions to align mold or shell 

sections. 

Mother Mold (Mold Shell): The rigid 

shell over a flexible mold that holds the 

flexible mold in the desired configuration. 

Model: The original shape over which a 

mold is made. 

Parting Line: The line where sections of 

a mold or mold shell divide. 

Release Agent: A coating applied to 

prevent liquid rubbers and resins from 

sticking to surfaces. 

Resin: A liquid that can be cured to a 

solid plastic. 

RTV: Room temperature vulcanizing. 

Shims: thin strips of material used to 

form parting lines. 

Undercuts: A configuration such as an 

overhang between two mated surfaces, 

such as a mold and model, that tends to 

prevent them from separating when 

pulled apart. Flexible mold materials 

allow molds to be made with limited 

undercuts because the flexible mold 

material bends as the part is demolded. 

Accessories 


65

Polyurethane RTV Mold Rubbers . . . . . .32-39 

Poly 74, Poly 75 & Poly 77 Series Rubbers 

Our Most Popular Mold Rubbers! With hardnesses that range from a soft, 

stretchy Shore A~20 to a very firm Shore A~90, these rubbers find innumerable 

uses as tough, long-lasting mold rubbers or for making rubber 

parts, forms or stamps. Many of these systems have 1:1 mix ratios and 

all are easily mixed by hand or can be machine dispensed because of 

their low viscosities and other user-friendly characteristics. These 

polyurethane rubbers are designed for casting concrete, plaster, wax, and 

resins/foams with the use of appropriate release agents. Poly 74-20 has 

been designed for high-volume concrete casting where the highest level 

of elasticity and performance is required. Poly 74-30 is ideal for wax 

casting in foundry applications. Firmer versions of the 74, 75 and 77 

Series rubbers are recommended for casting plaster and concrete as well 

and are chosen based on hardness and other specific physical properties 

needed depending upon the size, shape and nature of the master being 

duplicated or part being cast. Consult Polytek's technical support staff for 

assistance in choosing the right rubber for your application! 

Polygel ® Brushable/Sprayable Rubbers - Patented Polygel mold rubbers 

are 1:1 mix liquids that thicken upon mixing Parts A and B to a 

brushable or sprayable viscosity. Polygel 50 can be applied about ¼-inch 

thick while Polygel 35 & 40 are thinner for best detail penetration. With 

Polygel Spray 35 & 50, you can make a large mold in an afternoon and 

cure it overnight. 

Poly GlassRub - GlassRub 50 is a clear, pale-blue, glass like rubber for 

casting flexible art objects or for cut molds. 

Poly-Fast 72-40 Series Rubbers - These fast-setting rubbers (8-hr 

demold) can have varied hardnesses by changing mix ratio or adding Part 

C. Can be thickened for brush-on molds with Cab-O-Sil ® or Part D. 

Poly 81 Series Rubbers - High-performance, RTV, elastomers for parts, 

tools and molds. Low moisture sensitivity. Hardnesses of D45 and A90. 

Casting Plastics/Resins . . . . . . . . . . . . . .46-56 

EasyFlo Series Plastics - Easy 1:1 by volume mix ratio, odorless, 

resins cure to a white or clear plastic in minutes. EasyFlo 60, 95, 120 & 

Clear are super low viscosity, fast casting plastics: great for rotocasting 

and bubble-free parts. Also used for making cold-cast bonded bronzes. 

Poly 15 Series Casting Resins - Filled Poly 15-3 and faster 15-3X are 

excellent for casting parts, molds and tools. Poly 15-6, 1511 and 1512X 

make strong, lightweight mold shells. Poly 1510, 1511, 1512 and 1512X 

are water thin, with a great thermoplastic feel for prototypes. Poly 15-8 

is aluminum-filled for applications demanding heat-resistance. 

Poly-Optic ® 14 Series Crystal Clear Casting Resins - Poly-Optic 1410 

and 1411 are non-yellowing, Shore D85 plastics. Poly-Optic1420 must 

be heat cured and is buffable. Poly-Optic 14-70 is a clear rubber with a 

Shore A70. 

Poly Lite Cast - Has a wood-like feel and can be carved, cut, sanded and 

drilled. 

Poly Plasti-Flex - A flexible plastic for decorative trims and castings. 

Polygel ® Plastic-75 & Polygel ® Shell - Easy, 1:1 mix ratio, use these 

resins for making mold shells fast. 

PolyFoams - Cast these easy (1A:1B) rigid & flexible foams in closed 

molds packed to 4-20 lb/ft 3 densities to produce parts replicating wood, 

terra-cotta, stone, etc. Use in PlatSil or TinSil molds. 

Liquid Rubbers & Plastics 

for Mold Making & Casting 

Silicone RTV Mold Rubbers . . . . . . . . . .40-45 

TinSil ® 70 Series Silicone Rubbers - Many products, from soft A10 to 

firm A60 hardness. Best for casting resins and 70-60 is acceptable for 

casting low melting metals. Consider TinSil 70 Series systems for best 

economy. 

PlatSil ® 71 & 73 Series Silicone Rubbers - Consider platinum-cured 

PlatSil 71 & 73 Series for highest performance. Several easy-to-use, 1:1 

mix ratio systems with 4-hour demolds are available. 

PlatSil ® Gel-10 Silicone Rubber - Translucent, soft silicone for delicate 

casting projects and special effects. Use to make simulated skins and 

prosthetic appliances that can be applied directly to an actor or for aniimatronic 

effects. 

Specialty Molding/Casting Materials . . .57-60 

Latex Rubber Products - Poly Latex 60 is a one-part, thickened, natural 

latex for brush-on molds that are strong and durable. When thinned 

with Poly Latex N, Latex 60 can be sprayed using an inexpensive cup 

gun. Poly Latex False Face Compound is a one-part, high strength, casting 

rubber for novelty masks, flexible sculpture and animatronics. False 

Face can also be used for dipped molds. 

Poly Wax 15 and Poly Skin-Wax - Poly Skin-Wax has a very low melting 

point with good toughness after cooling for making molds of hands, 

feet and delicate objects with limited undercuts. Poly Wax 15 is mineral 

filled for casting in most rubber molds to make recarvable models. 

Hydrogel ® N Mold Compound - Mix this powder with water to make a 

rubbery mold in minutes. Yields excellent mold impressions if plaster or 

wax is cast right after setting. Safe for body contact. 

Epoxy Resins and Curatives - Polypoxy ® 1010 is a general-use, low 

viscosity, epoxy resin. Mix with Poly Cure 1212 and bronze or other 

metal powders for production of cold-cast bonded bronze in rubber 

molds. Call for information about other epoxy systems. 

Accessories . . . . . . . . . . . . . . . . . . . . . . .61-64 

Polytek offers many accessories so you can obtain all your mold-making 

supplies from a single source! 

Pol-Ease ® Release Agents - Aerosol Pol-Ease 2300 & 2500 and waterbased 

Pol-Ease 2601 allow for easy release of rubbers from models and 

resins from molds. Pol-Ease 2650 is best for high volume concrete and 

plaster applications. 

Poly Adhesives & Bonding Agents - PolyBond is a flexible, high performance, 

polyurethane adhesive for many applications. EpoxyBond & 

Quick Stick are epoxy systems for similar rigid bonding applications. 

PolyFiber, Bronze and Other Fillers 

Safety Equipment - Polytek sells gloves, coveralls, solvent cans and 

more. Work safe! 

Mixers, Scales, Books and Videos & Other Equipment 

Our latest training DVD demonstrates various mold making techniques 

and is only $5.95! Polytek can suggest rotocast machines and meter-mix 

pumps/sprayers to dispense liquid rubbers & plastics to meet your particular 

requirements. Please call to let us help! 

See Our Low Cost Trial Unit Order Policy - p. 65

Polytek catalog - Sculpture Workshop

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