How do I coat a screen with liquid emulsion?
Seems like it should be a fairly simple step one, step two, step three
ask any 10 printers how they coat their screens, and you
might very well receive 10 different answers
. Let’s take some of the
mystery out of this process.
First, let’s assume we are using either
dual cure or pure photopolymer emulsion.
Our approach will be finding a method that is both efficient and
effective. Some recommend a multiple coat method – one side, both sides,
or coat-dry-coat. This multi-coat approach can be attributed to a
couple of reasons. The screen printer (or the person who taught him) may
have had experience with older diazo emulsion and struggled with
shrinkage of the emulsion on the mesh causing pinholes. Or the printer
has struggled with pinholes even using dual cure or pure photopolymer,
and has fixed the problem by applying more emulsion as a type of
Today, modern emulsions offer good coverage
without the shrinkage experienced with earlier diazo emulsions. And if
the issue is pinholes, proper
and protecting the screen from contaminants is the real fix, not
applying more emulsion to the problem. Extra emulsion means more
material cost, longer coating and drying times, and more difficulty
reclaiming the screens after production.
In this article, I’ll recommend you
coat screens with just one pass on the print side and one pass on the ink side (watch the video).
Just another opinion from a screen printer out there in the world? This
method is based on years of production and being fast, efficient and
effective. Coating one pass on each side of your screen should give you a
quick and perfectly effective screen, and ready for a full production
1.) Pour your emulsion of choice into a scoop coater with at
least 1” clearance from the inside of the screen frame on each side. (If
the inside width of your screen is 18”, the scoop coater should be no
more than 16” wide.) The sharp side of the squeegee will go against the
2.) Stand the screen up on a table and hold with your
left hand (if you’re right handed). With your right hand (or vice versa)
pick up the loaded scoop coater from the center, take care not to spill
emulsion out of either end. The operator in the
video is left handed,
by the way, so don’t be confused.
3.) On the print side of the screen, place the scoop coater against the scoop coater
toward the mesh until a bead of emulsion touches the fabric across the
entire length of the scoop coater. Do not roll the scoop coater over so
far that the flat plastic sides of the scoop coater rest against the
mesh. Rolling too far forward may cause the scoop coater blade to pull
away from mesh during coating and result in a heavy emulsion lay down or
emulsion spilling out onto the mesh.
4.) Pull the scoop coater up the
screen slowly, allowing the thousands of tiny openings in the mesh to
be filled with emulsion. (Experienced printers who come to my classes
always seem coat the screen as fast as they can pull the scoop coater up
5.) About 1” before the inside edge of the frame, stop, roll
the scoop coater back to allow emulsion to pour back in, then slide the
scoop coater up and then away from the mesh.
6.) Turn the screen around and
Any excess emulsion on the screen, on the sides of your
coating stroke, can be carded off with a small square of cardboard or
plastic. This will speed drying of the screen and prevent emulsion from
dripping down onto another screen during the drying process.
Now, dry the screen in a
horizontal position either in a professional or homemade drying rack
with the print side down (just as the screen is placed in your
printer). Print side down will give you a heavier deposit of emulsion on
the print side of the screen so that you have a nice smooth surface
touching the shirt being printed.
If you make a mistake in
coating, it’s okay to clear any excess emulsion from the coated area
with the sharp edge of the scoop coater. Screen coating is a very
forgiving process, so your repaired coating job may not look perfect,
but it will work perfectly well.
When you are finished coating
your screens, pour the excess back into the emulsion container for reuse
later. Wash out the scoop coater immediately with water and allow it to
dry upside down on a towel.
Coated screens will last about two weeks in
a dark room or light-tight container.
Coating is one of the
processes in screen printing that tends to frighten new participants.
(I’ve witnessed many a shaking hand during this part of class.) Just
remember that proper preparation and a simple inside and outside stroke
will result in a quick, easy and perfectly functional screen, ready to
load on your press.