The most prevalent technique for color reproduction involves the use of a separate screen for each color to be reproduced. This is effective in printing images that have a limited palette and contain no halftones. Cartoons, type, and line art can be easily reproduced with simple spot seps.
If the images are to be printed on darker garments a thicker coat of ink
will occasionally suffice to yield the desired opacity. More often, shirt
printers will use and 'underprint' to provide an opaque base for the colors
that follow to lay on top of. This 'underprint' must be dried during the
printing process to keep the following colors from becoming contaminated
and to maintain opacity. This step is called 'flashing' and involves the
use of in-line infrared or quartz heating units. Creating the underprint
for simple spot seps is relatively simple but the exact specs depend on the
printers technique.