Put into the simplest terms possible, discharge ink is a water-based ink that is used to replace the color of dye in the shirt fabric. For example- a black t-shirt- to become a black t-shirt the factory used black "dye" to make the shirt black- and if we use red discharge ink- the red will bleach out the black dye and replace the dye with red. So now the fabric of the shirt is no longer black- but red. Discharge ink is mainly used for cotton shirts. But... we have used discharge ink on some 50/50 blend shirts. Any shirt that is extremely soft may have used discharge printing to get the real effect ? it makes it easy to print colors onto darker clothing without having to go over the top with the ink usage to get the desired effect and style.
Discharge ink is effectively just normal water base ink with an activator included to really get it going. Made from Zinc Formaldehyde Sulfoxylate, this works on the clothing to remove the old dye and this creates kind of bleaching effect which makes it much easier for the colors of your actual print to then take place and really look grand. It allows the image to look just brighter than the base color of the fabric, making it easy to spot the image but helping it blend in perfectly.
Here are some pointers about screen printing with discharge ink-
Discharge inks require more air flow to dry or cure the inks than the standard plastisol inks do. To fully cure discharge ink you must drive or force the water out of the inks before they can be cured by reaching the 320 degrees.
You want to make sure that the t-shirt is being cured with a heating system that uses forced air as it will dry the water out of the ink so that the ink can then be cured.
Discharge ink use force air to cure or dry.
Discharge ink work best on dark cotton garments
Discharge ink can be mixed with pigments to create specific pantone shades- but this can be very tricky, as some fabrics and dyes work well with discharge and others do not
Discharge ink can "dry" in the screen- But there are additives to keep the ink "wet" longer- These additives have made printing with discharge inks MUCH easier-
Discharge ink is used mainly on cotton shirts
Discharge ink requires mixing