Mastering High-End Simulated Process Printing - Impressions

Mastering High-End
Simulated Process
Printing
Learn how to achieve excellent color
accuracy and create faster, more
consistent production runs with this
detailed tutorial.
By Mark Coudray, Contributing Writer
It’s no surprise that simulated
process printing is getting more and
more complex. Customer demand for
high-quality, accurate color is at an
all-time high today.
In this Tech Tips newsletter and accompanying
video, you’ll learn some little-known tips and
tactics to help you achieve excellent color
accuracy with your next simulated process job.
Not only will you experience an increase in
your print quality, but you’ll also notice a faster,
more consistent production run.
JERZEES ® NEW HiDensi-T TM collection is made with 50% denser
fabric and a higher stitch density per inch for better printing detail
retention on four-color and simulated process printing. The 5.0-ounce,
100% cotton preshrunk jersey T-shirt (style 363MR shown here) has
a tear-away label; seamless body with set-in sleeves; 1x1 seamless
ribbed crew neck collar; two-needle cover-stitched front neck; taped
shoulder-to-shoulder and two-needle hemmed sleeves and bottom. It
is available in four styles ranging in sizes youth 2/4 through adult 5XL
in up to 23 colors.
Great prepress is a given, but to achieve excellent simulated process printing you need a garment with an excellent
print surface. You’ll find a great platform in the new JERZEES ® 363MR HiDensi-T TM 100% Cotton T-shirt. This is
the garment we’ll be using to demonstrate what a really great simulated process job should look like. We’ll also be
comparing the same print on a lower-quality garment so you can see the difference.
PREPRESS
Great simulated process prints begins with the color separations. The ease of making general-purpose color
separations from Adobe Photoshop or Illustrator is only the beginning. Today, there’s a significant tendency to handle
the color separations in your own art department. This generally is a good approach until you start doing work where
critical color is required.
An experienced color separator can create outstanding separations in Photoshop as long as he knows what he’s
doing. Sadly, most designers don’t have enough color theory or practical printing experience to really master the color
separation process. By mastery, I mean, “Color In = Color Out.” Most separations are, at best, an approximation.

Critical color benefits from professional color separation
from companies like Netseps.com or Serichrome Seps.
These companies have been producing critical color
separations for more than 25 years, and the price today
is a fraction of what it used to be.
Outputting your digital color separation files is the next
step. Using the correct halftone settings is crucial for
obtaining the best results. I recommend:
• Dot Shape: Elliptical or Diamond
• Dot Angle: 22.5° or 67.5° for all colors
• Frequency: 55 lpi for automatic printing; 45 lpi
for manual
Your RIP’s quality and your ink’s opacity are very
important. Vellum output is not recommended for
halftone printing. The dots are too thin and easily
burn through. The inkjet film should be very dense. To
quickly check for adequate opacity, hold a piece of film
up to an overhead fluorescent light. Look through a solid
printed portion of the image. If you can see any of the
outline of the overhead tube, the ink is too thin and will
burn through. It should be solid black.
The correct screen mesh count will make all the
difference when it is time to print. Mesh is sold by mesh
count, thread diameter and weave type. Underbase for
darks can be either 180.48 PW (plain weave) or 225.40
PW. I prefer the latter. Overprint colors are printed with
either 280.34 PW or 305.34 PW.
Tension on all screens should be 25 N/cm. Tensions
below 20 N/cm would yield inconsistent halftone results.
Maximum resolution is obtained with a dual-cure diazo/
photo polymer emulsion. The exposure is slower than
pure photo polymer, but the dot structure is much better.
Coating the screen two passes on the print side followed
with two wet-on-wet passes on the squeegee side will
give a good stencil profile for the halftones. If your coating
is too thin, you risk increased moiré. Dry the screen with
the print side down with plenty of filtered air circulation.
When it comes to exposure, a UV-rich light source is
very important. Use either mercury vapor or metal halide
designed for screen printing. The light should look
bluish-purple. If it has a yellow cast, or if you can see a
filament in the light bulb before you turn it on, you don’t
have the right kind of light. Follow the manufacturer’s
directions for exposure testing to assure you are not
overexposing or underexposing.
Washout can make or break your job. After exposure, wet
both sides of the screen with water and rub both sides
with your hand. Wait at least one minute before you wash
out the screen.
This step allows the unexposed emulsion to absorb
water and soften. After a minute, wash out the screen
with a sharp fan spray from a garden hose. Do not use a
pressure washer. Wash from the print side, starting at the
top and working your way across the screen and down.
Always follow the same sequence for consistency.
When you’re done, blot the inside of the screen with blank
newsprint. You can buy this at a store that sells shipping
supplies. Any emulsion color coming off on the paper
indicates under-exposure.
Allow the screens to dry with cool air blowing across
them. A simple box fan works well for this. After block out,
pin holing and taping, the screens are ready for the press.
PRE-PRODUCTION PRINT
A triple durometer 70/90/70 squeegee gives excellent
control and print quality. The softer 70 durometer
compensates for surface irregularities, while the harder
90 durometer keeps the blade from flexing excessively.
Always sharpen your blades before a halftone run. The
desired sharpness is reached when you lightly draw
your fingertip over the edge of the blade and can feel the
individual ridges of your fingerprints.
Next, look down the length of the blade. It should be
perfectly flat and straight, with absolutely no waviness.
The combination of a sharp, flat blade will assure

minimum squeegee pressure and smooth, even printing.
The inks you choose for simulated process printing
can range from transparent to translucent to opaque. I
recommend translucent inks where all the colors have
the same level of translucency. The value I recommend
is 25%, which means it is ¼ of the way toward opaque.
Many printers use opaque inks for simulated process
printing because they are easier to print with, but are less
accurate in matching with the original art.
When an ink is opaque, the physical color blending
is poor. The overprint color is shifted toward the color
that is more opaque. So mixing red over yellow will
give a very strong red-orange color. Printing yellow
over red will give a very strong yellow-orange. Using a
25% translucent ink for both will give a neutral orange
regardless of the print sequence.
Finally, the inks you use should be fairly stiff, yet yield
under light squeegee pressure. This characteristic is
called thixotropy. It’s important because this is what
allows us to print sharp, clean, halftone dots that don’t
squash when other colors are printed on them.
INK TIPS
To get great halftones, try applying some sharping base
to your ink. This can be accomplished by adding 2% by
weight of clear, high-density gel to any ink. A very small
addition will dramatically increase halftone sharpness.
Another key to achieving maximum image quality is to
ensure your inks are at the correct printing temperature.
Plastisol inks are made of plastic resins. The colder the
temperature, the stiffer the ink. As the ink warms up, it
gets softer and thinner. The flow of the ink is continuously
changing until the temperature reaches 90°F (32°C).
It is impossible to control color accurately with ink
temperatures below this point.
We use our flash cure units to preheat the shirt platens to
130°F (±55°C). With the print head in auto index, rotate
the press until the ink temperature is at the desired point.
Use an inexpensive IR digital pyrometer to measure this.
With warm platens, the flash time is reduced to less than
1 second using the mesh counts I’ve recommended.
All of these preparations are important, but they are of little
value unless the garment has enough fiber mass to accept
the halftone dots. Most T-shirts are only 65% fiber mass.
However, the JERZEES ® 363MR HiDensi-T TM 100%
Cotton T-shirt has excellent fiber mass. Having your
halftone dot land on the yarn bundle assures minimum dot
gain and maximum image sharpness. You also need less
ink to achieve greater color and maximum image detail.
Careful attention to color separation, prepress and setup
will ensure excellent results when printing on an
ideal T-shirt surface. The high fiber mass and smooth
surface of the JERZEES ® 363MR HiDensi-T TM make
it a great destination for your critical color simulated
process images.
step-by-step to VIew a short VIdeo on the process of creatIng sImulated process prIntIng
detaIled In thIs newsletter, please clIck here.
step
1
A good 70-90-70 durometer
squeegee gives you a perfect
blend of conformable edge and
controlled blade bend. This allows
you to concentrate the squeegee
edge on the halftone with minimum
squeegee pressure for the
sharpest, cleanest print.
step
2
After washout, the screens
should be blotted with blank
newsprint to absorb any water in
the mesh. This is a gentle way of
making sure all water is removed
from the exposed screen without
damaging the halftone image.
step
3
Here is an excellent example of
the fine, smooth surface of the
JERZEES ® 363MR HiDensi-T TM .
Note the excellent halftone
sharpness and how every dot
prints perfectly on the garment
surface.

step
4
step
7
step
10
In this close-up of the printed
surface, the dots appear rough
and broken. This print was done
before the minimum printing
temperature of 90°F was reached.
In this close-up of the final print,
notice the complexity of the color
change. It would be impossible
to achieve this without completely
accurate translation of the
halftone information.
Stir ink vigorously with a spatula
and then lift it out of the ink. You
should have a supported ink
strand of 1 inch to 1 1 ⁄8 inches
suspended from the bottom of
the spatula.
step
5
step
8
step
11
High-end simulated process
printing involves accurate color
reproduction. Our test image has a
wide tonal range of white to solid
black, and subtle color changes.
In this microscopic halftone
close-up, you can clearly see the
integrity of the halftone and the
complete transfer of ink to the
garment surface.
Thixotropic ink will support a
vertical ink cross section when
you slowly drag a spatula
through it. If the ink walls
collapse quickly, add up to 2%
high-density clear gel to the ink.
step
6
step
12
Here is another example of the
print surface of the JERZEES ®
363MR HiDensi-T TM . Note the
regularity of the halftone dots
both in size and in arrangement.
Another closely held secret to
great printing is to ensure the ink
temperature is between 90°F
and 120°F. Preheat your pallets
to 130°F to warm the ink in the
screens before printing.
Mark Coudray is a recognized industry veteran and expert on color separation and halftone printing. He is a sought-after consultant
and industry writer with more than 350 published pieces during the last 35 years. You can read more of Mark’s work at HalftoneSecrets.
com. He can be reached via e-mail at Coudray@coudray.com where he welcomes your comments and observations.
step
9
To achieve great printed halftones,
mesh tension between 25
and 30 N/cm is essential. Tension
below 20 N/cm make it
impossible to control squeegee
pressure and ink transfer.