Discharge Printing is a process in which a discharge ink is used to deactivate/replace a dyed fabric. It is also called Extract Printing as the dye of the fabric is removed, and a lighter colour is achieved. For example, we could dye a fabric black, and use a discharge print in white to print a white motif on the black fabric (a reactive or pigment printing technique would not show a lighter colour on top of a dark one). The discharge chemical comes in a few colours, so you could print red on black (the red “discharges” the black and replaces it with red). Other colours include pink, blue, yellow, grey, and olive green.
The discharge ink used is a clear liquid deactivator that contains zinc formaldehyde sulfoxylate which is what bleaches or reduces the shade of the original dye.
Wash care for discharge prints on cotton: wash in cold water with a mild detergent, and rinse shortly after (don’t soak). For discharge prints on silk, you can wash with a very dilute soap in cold water and then line dry or send it for dry cleaning if the fabric is prone to colour bleeding.