Jeff Holland - November 1984
There are two basic methods for small scale screen printing.
is used most often for sign and
marker applications. The other technique, Lacquer
, is commonly used for textiles and
In this method you are effectively making a "negative"
from a photo or hand drawn positive. The result is a
screen with the black areas of your drawing or "positive"
washed out to allow ink to pass through. There are a
number of ways to prepare the "positive".
If your copy is solely text, a printer can prepare the
text, typeset it, and produce the copy for you. If a
photograph or very fine line drawing is involved it
must be reproduced in "half tones", a dot
grid pattern producing black and white patterns similar
to newspaper photos. A photo or drawing can also be
reproduced from a photo negative developed on "ortho"
or Kodalith film, processed in the darkroom.
Another way to prepare a positive is to draw directly
on acetate with opaque ink. There is a red block-out
ink made specifically for this, but a high quality black
india ink works as well. The acetate then becomes your
"positive". Lettering can be accomplished
with chartpak rub on lettering.
The emulsion is applied on the screen in even, thin
coats. There are two commercially available ones, Speedball
or Advance-Excello, both available at Art Supply houses.
Both come as two part solutions- a glue-based resin,
and ammonium bichromate to sensitize the emulsion. This
is available in quart and gallon sizes. The choice is
determined by economy. You only need I cup of resin
to complete two 18" x 24" screens. With either
kit, make up only as much as you need because, once
sensitized, the emulsion has a very short shelf-life.
Wash the silk first with mild soap and let it dry. Apply
the emulsion in room light, with a piece of cardboard.
A THIN even coat is best. Get screens to dry in a DARK
place such as a cupboard, bottom side down (raise up
with tacks or cardboard). Drying time takes 1-3 hours.
The screen should be exposed within 24 hours.
Exposure is most easily carried out by using a #2 photo
reflector bulb with a pie plate reflector sound it.
Regular 150 watt household bulbs can be used but take
one hour or more exposure time. A general rule of thumb
to place the bulb over the screen is the light source
should be equal to the diagonal cross-section of the
original being exposed. The screen should be placed
on dark or black paper. Place the "positive",
then sandwich with a piece of glass or plexi-glass for
good contact. A general exposure time for an 18"
x 24" screen with a photo bulb is approximately
15 minutes. An exposure test similar to a darkroom timing
strip is recommended for the first trial. Chemicals
and emulsion thickness, light source and image density
are all variables.
The emulsion is then washed out with a lukewarm-cold
water spray. The image being printed should be completely
"open" if done
properly. The screen
should be taped up on the sides and checked for pinholes.
You can use "blockout" or tape or mask off
areas you don't want to be printed.
Printing can be done on metal, paper, or plastic. There
are plenty of Ink types to choose from, including water
based commercial inks. One thing to keep in mind is
that it's important not to let the ink dry out in the
screen. If an extended run is planned, there is an ink
"extender" that slows drying time down.
Set up the screen so that easy, repeatable results are
possible. This usually means having it hinged on a backboard
with the place for printing registered with masking
tape and cardboard stops. Use a squeegee large enough
to complete the pass in one stroke. More than one pass
will result in bleeding of the ink beneath the screen.
It helps to have the screen raised off of what you're
printing by an 1/8th of an inch.
Water based inks clean up with a special mild soap solution.
Enamel ink cleans up with kerosene or mineral spirits.
USE PROPER VENTILATION (and common sense). The screen
itself can be cleaned of the emulsion with a solution
of 1 to 1 household bleach.
Lacquer Film Acetate Stencils
Lacquer film is a thin layer of lacquer on a plastic
base that you cut away with an x-acto knife to produce
a stencil. The stencil is adhered to the screen with
lacquer thinner and acetone. The tricky part is not
getting the film saturated with solvent as you draw
it into the screen. You can blot with one rag barely
damp with solvent and another dry one. Work from the
center. Let the film dry before peeling away the plastic.
This method is commonly used for quick graphics and
textile printing because of the ability to use water
soluble inks. Fine lines can be produced depending on
how steady your hand is