This term is relevant for screen printers that
are printing on “dark" color garments.
An underbase is a layer of ink (generally white
or other light color) that is printed as a "base" on a dark shirt
for other colors to sit on. This gives the top colors more
brilliance. Since the underbase is generally a high opacity ink, it
is flash-cured before the top colors are printed over it. Not only
does underbasing slow production, but it is often an extra color
(which costs more money). Underbases are also called an underlay
(very common) or a mask (not as common).
Tips of screen printing on dark colored
1. light color inks on dark goods generally
require a base white screen and a flash.
2. Designs that have white in the image will
only need a flash.
3. Any fluorescent inks need a white
Here are the reasons:
Shirts are fabric, and when ink is layered on
it soaks into the fabric resulting in a muted look. Flash
curing dries the ink enough to lay a second coat on top of the first
of the fabric) resulting in a brighter color.
Note that the ink also will feel thicker, because it is.
Another reason for flashing is dye migration. This is most often
seen on red shirts as the dyed
color of the shirt (especially with white ink)
tends to “migrate" through the ink and turn it pink. Flashing
reduces this dramatically.
There is no underbasing without a flash-cure
unit (or some other method to flash dry the fabric). If you plan to
do a lot of flashing make sure the unit is large enough to meet your
You should position the flash unit so that you
can get a cure in a matter of seconds. Plastisol will cure to the
touch at around 120 degrees C (consult with your flash unit
manufacturer for proper temperature suggestions based on their
machine). If you fully cure the fabric, the top colors may not
adhere properly and can flake off when washing the shirt. The
length of time for the curing process is critical.
You may also want to learn about
direct to garment printing
machinery and processes.