What is Discharge Printing?
Discharge printing: The simplest explanation? Discharge ink is a water based ink that is formulated to deactivate the dyes used on natural fabrics ( cotton ). It's like bleaching out the original dye and replacing it with the color you want.
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. The main advantage of this process is the soft feel, however another equally great advantage is the ink will never fade or crack, it lasts as long as the shirt!
Discharge Ink, Sounds nasty, but its Really Cool!
Discharge printing ink 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. Be aware that some colors will not end up as an exact match for the ink color you want.
When we need to print a color rather than clear discharge ink we will add water based pigments to the ink in order to remove the fabric color and replace it with the color of our choice. This allows us to maintain tight registration and bright prints on dark fabric without the use of white underbase ink. For the ultimate in soft colorful prints, pigmented discharge is the way to go. This process is great for fashion oriented prints, and clothing brands.
Here is a quick video to help you understand the process.