There are many different variations of liquid emulsion, but to keep the subject
simple there are three basic chemistries and a variety of percentages of solids.
Liquid emulsion is mostly water. A vendor can offer you a low price by providing a low
percentage of solids, that is, high percentage of water. You will know,
because the emulsion flows more easily and cleans up more easily. High
resolution work like half tones and fine details need high solids emulsion
to form the image that is in the positive. A lower percentage, less expensive
liquid emulsion can be used for printing text and spot colors.
The original chemistry is diazo. These are liquids where a powder is added to the
emulsion. Until the powder is added, the emulsion is inert that can be
safely stored for a long time. Once the two are combined, any emulsion
not used should be stored in a cool place like the refrigerator to prevent
spoilage. Regardless, the emulsion will have a short life, if not used. These
inks are designed for plastisol inks.
When an acrylic is added the emulsion becomes water and solvent resistant. These
are called dual cure emulsions designed for plastisol, water based and solvent
based inks. The exposure time is similar to diazo emulsions.
The newest formulations are photopolymers designed for plastisol inks only. These
emulsions expose much faster than diazo and dual cures. In some cases,
photopolymers expose in one quarter of the time. The way to find out
how fast any emulsion or capillary film exposes is to test with an exposure
The coating thickness is determined by factors like mesh count, thread diameter, angle
of scoop coater, pressure on scoop coater and speed with which the scoop coater
is used. Being consistent is very important to get consistent film coatings
of emulsion. If you notice the emulsion is darker in the center of the
screen, that means the emulsion is thicker. Low mesh tension is the cause,
and not your coating technique.
To read more, see:
“Evaluating Liquid Emulsion”