The simplest explanation? Discharge ink is a water based product that is formulated to deactivate the dyes used on natural fabrics.
What it Does.
You have probably seen many shirts with a very soft print that looks like the color of natural cotton – this is discharge printing. Discharge screen printing can be used to print colors on dark garments that in the past would have required an additional layer of white ink in order to achieve proper opacity of top colors.
Discharge Ink, Not Some Gross Stuff.
In its basic form, discharge is a clear ink with an activator added. The activator is Zinc Formaldehyde Sulfoxylate, and this is what causes the dyes in the fabric to be deactivated. Printing a straight discharge ink typically ‘bleaches’ the fabric down to its natural color, a slightly off white. Discharge inks work well on fabric that is dyed with reactive dyes, although some dyes are more resistant than others, often those colors are in the kelly green, purple and royal blue families. When discharged, these resistant fabric dyes yield a more muted print that is usually a lighter tint of the base fabric color.
When we need to print a color rather than clear dischrage ink we will add water based pigments to the ink in order to essential re-dye the fabric with the color of our choice. This allows us to maintain tight registration and bright prints on dark fabric without the use of an underbase. For the ultimate in soft colorful prints, pigmented discharge is the way to go. We use discharge inks so much that we just call all of our inks ‘water based.’ If the print goes on darks we add the discharge activator, otherwise it is the same ink chemistry.