Static Dispersing Glazing - Picture Framing Magazine

Preservation Practices 

by Hugh Phibbs 

86 PFM _ December 2004 

Static Dispersing Glazing 

Static electricity was not a major factor 

in picture framing, until acrylic 

sheet was introduced as a glazing 

material in the last century. Glass does 

have potential for holding a static charge, 

but is crystalline enough that its potential 

is low. Plastics are 

more amorphous, less 

crystalline, and that 

makes them much 

better at maintaining 

a static charge. When 

the surface of a plastic 

sheet is brushed with 

most anything soft, 

electrons will be left 

on its surface, creating 

the static field. This is 

especially true if the 

atmospheric conditions 

are dry. The static 

will attract any 

small particle that has 

a positive charge. This 

includes loose or friable media, flaking 

paint, or supports that have degrading 

surfaces. 

The attraction that a static charge can 

exert may extend for several inches; making 

it especially problematical for framing, 

since the planar nature of a picture frame 

makes it difficult to space the glazing far 

enough from the framed work to ensure 

that the reach of any static charge will not 

affect the framed item. Acrylic sheet has 

Static attracts any small 

particle that has a 

positive charge. 

This includes loose or 

friable media, flaking 

paint, or supports that 

have degrading surfaces. 

significant advantages for framing—lightweight, 

shatter-resistant, available with 

UV filtering components, and thermal 

insulation—and it should be a mainstay 

in any operation in which valuable items 

are framed. How can its static potential 

be addressed and 

how can the phenomenon 

of static 

in framing be 

understood? 

When glass 

became more 

widely available, 

with the advent of 

sheets made of 

flattened cylinders, 

works on paper 

were placed 

between the glass 

and a wooden 

backing board. 

This combination 

ensured the 

destruction of many of the items they 

enclosed. The wood emitted acids and 

peroxides and when sun shone through 

the glass, the temperature of the work on 

paper rose, before the glass warmed up. 

This meant that as moisture left the 

paper and the wood, behind it, that 

moisture might condense on the still 

cool glass. 

Tim Padfield, a British conservation 

scientist, has reasoned that the black

areas in the framed paper would heat up most rapidly, 

since dark materials absorb heat more than light ones 

and that such differential heating would result in a pattern 

that would show up in the salt that forms from the 

sodium that is driven from the glass by water. This pattern 

can be seen on glass that has been left on frames for 

many years. However, this salt will cling tightly to the 

glass and should not pose much of a physical problem 

for the framed paper. The static 

that built up on the glass would 

pose a problem for media such as 

pastel and charcoal, but physical 

contact and transfer were a 

greater threat. 

In the past, knowledge of this 

problem led to unusual techniques. 

For example, framers in 

the 19th century were well aware 

of the fact that pigment could 

transfer from the art design to the 

glass. They understood that the 

greatest risk came from the possibility 

that pigment might be 

moved from one part of the 

design to another, blurring it. 

One solution they had for this 

problem was placement of the 

pastel directly behind the glass. 

To ensure that there was minimal 

movement of pigment among parts of the drawing, they 

kept the pastel snug to the glass by placing cotton 

between the back of the paper and the wooden backing. 

Even though this resulted in a certain quantity of the 

pigment moving from the design to the glass, it guarded 

against loss of clarity in the design. 

Modern framing has used deep matting and spacers 

to address the contact transfer issue and until recently, 

went on the assumption that the static potential of glass 

was not a significant problem. That view was altered 

when staff at the Tate Gallery in London observed that 

the process of taking tape off of glass created a significant 

static charge. This meant that the tape that had 

been used to prevent shattered glass from coming loose, 

if there was breakage during shipment, presented a 

problem. In short, to maintain safety, the pastel would 

have to be unframed, before the tape could come off of 

the glass. Museums have used laminated glass to avoid 

both breakage and taping issues. Such glass has been 


An anti-reflective, 

static dispersing acrylic 

can be cut with hand 

tools or a wall cutter. 

Cutting the material 

with a saw may cause 

some of the brittle 

surface coatings to chip. 

expensive and hard to work with, since few have had the 

ability to cut it to size. 

A simple solution to both problems comes from 

shatter-resistant acrylic sheet that has a static dispersing 

coating of metallic material on its surface. Both glass 

and acrylic can be coated with different materials, for 

different purposes. Alternating layers of silicates and 

titanium dioxide can be used to change the phase of 

reflected light as it leaves the glazing. 

This makes the reflected light opposite 

in phase to the incoming light 

and thus, the reflection is cancelled. 

This produces the anti-reflective 

coatings that are so useful for glazing 

dark items. 

There are two processes for 

applying such coatings. The sheets 

can be dipped in a bath and the 

material can be baked onto the surface. 

Such coatings can also be 

applied with an ionic sputter coater. 

The first process can only be done 

with glass, while the second process 

can be done with either glass or 

acrylic sheet. To keep the acrylic 

from warping at the elevated temperatures 

inside the sputter coater, the 

use of acrylic that has abrasion resistant 

coating on it has been shown to 

work well. If another coating of a metallic compound 

such as indium-tin oxide is added, these metal oxides 

disperse any static that the sheet may encounter, rendering 

it static free. 

Static dispersing acrylic can be found in sizes up to 

48"x96" and thicknesses as great as 1 /4". It is used in 

clean rooms, where critical scientific and technical tasks 

are carried out. (This product can be found in the 

online catalog of McMaster Carr.) Another, even more 

useful form of static dispersing acrylic comes 41"x71" 

and as thick as 3 /16"; it has the advantage of anti-reflectivity 

and it is available with UV filtration. This material 

was developed for use in flat screen electronic devices, 

where the potential for static is quite high and the 

client’s investment warrants the use of premium materials. 

This latter material is available from Tru Vue, under 

the name Optium. Both the non-UV filtering and UVfiltering 

sheets of Optium are available in 1 /8" and 3 /16" 

thicknesses; the thinner of the two can serve the needs

of framers well, since most of the material they handle 

will be kept upright and will not encounter the potential 

problem of sagging acrylic that flat storage can entail. In 

museums, where UV filtration is handled by filtering 

glazing in the building and the use of lighting sources 

that emit virtually no UV, workers can use the thicker 

and more stable 3 /16" variety, to avoid flexing of the 

acrylic during flat storage. 

This anti-reflective, static dispersing acrylic can be 

cut with hand tools or a wall cutter, while cutting it 

with a saw may cause some of the brittle surface coatings 

to chip. It can be cleaned with alcohol and water and 

since it has no static it is the easiest glazing one can find 

to fit. 

The potential of anti-reflective, static dispersing 

acrylic for high end preservation is profound since it 

combines several sought after attributes. Its anti-reflective 

property will enable its usage for materials, which 

owners or curators might otherwise be hesitant to glaze. 

Its static dispersing potential makes it safe for use with 

unfixed pastel and other difficult to store media. These 

media can now be safely kept in frames, whether on the 


wall or on the darkened shelf. Its shatter-resistant 

strength means that it can serve as glazing for works 

that must be shipped. 

The complexities of making this anti-reflective, 

static dispersing acrylic are likely to prohibit significant 

decline in its price, but it is already less than half the 

price of low-iron, anti-reflective, laminated glass. As is 

the case with heat activated sealing foils, silica gel, and 

pollution scavenging materials, preservation framing 

benefits from technologies developed for other areas 

and we should be continually looking for other such 

useful adaptations as technologies evolve. ■ 

Hugh Phibbs, Preservation Editor, is the coordinator of graphics 

conservation services in the Department of Exhibitions and Loans, 

Conservation Division, National Gallery of Art, Washington, D.C. 

He has taught workshops for the National Conference, the AIC, 

PPFA, the conservation programs at Winterthur/University of 

Delaware, and the Smithsonian Resident Associates Program. He also 

compiled the matting and framing section of “The Book and Paper 

Group Outline.”

Static Dispersing Glazing - Picture Framing Magazine

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