Underbase

Print white ink straight onto a black shirt without an underbase and the design comes out gray and washed out, because the shirt's own dark fiber shows through every translucent layer of plastisol on top of it. This flash-cured coat of opaque white — sometimes a light gray or off-white, depending on the garment color — gets printed and partially dried before any of the actual design colors go down, giving every color above it a neutral base to sit on instead of the shirt's own dye.

This is why a two-color logo that would run as a two-color job on a white tee often quotes as three colors on a navy or black one — the underbase counts as its own screen and its own press pass, even though the buyer never sees plain white on the finished shirt. We've had customers push back on that line item until they see a side-by-side: the same red logo goes from dull brick on bare black cotton to true fire-engine red once it's backed by solid white.

Printers dial that white layer down to a thin, even coat — too heavy and it adds stiffness and a plasticky hand to the print; too thin and the garment's own dye bleeds through after a wash or two from dye migration. A quality shop flash-cures the underbase to a tacky, not-fully-cured state before the color coats go on, so everything bonds together in one final cure.

The common misconception is that an underbase is optional padding a shop adds to inflate the price. On any garment darker than a heather gray, skip it and the print looks unfinished and can shift color entirely after the first wash, because unprotected dye keeps creeping up through the ink for the life of the shirt.