The rule of thumb for curing plastisol ink is basically that the ink needs to reach 320º F for at least one minute. A flash unit is meant to cure only the uppermost layer of the ink so that a printer can print another layer of color without smearing the one underneath.

To illustrate further, imagine the ink layer as cake batter and the flash unit as a broiler. If the “cake” is supposed to bake for one hour in the oven but is instead broiled for 15 minutes, the top of the cake would be dark or charred, but the bottom of the cake would still be liquid.

Similarly, the ink may seem to be “dry” after being flashed for 15 seconds, but the underlying layer is not yet cured and bonded to the fabric, so when the shirt is washed, the ink may also wash off.

Thus, cure the ink correctly—that is, in a dryer—rather than by using a flash unit.

—Kieth Stevens, International Coatings