To “discharge” print a shirt is to use “discharge” ink and get the dye in the shirt to be neutralized. You add a catalyst to a specific type of ink and in the presence of heat and water the dye basically goes away. Only cotton discharges and not all cotton dyes discharge. We test shirts from time to time to see if they discharge and when we get a new shirt/color we test it.
In the following prints you can see shirts that almost entirely discharge and basically turn pretty close to white, some that don’t discharge that well and turn some medium color, and some that don’t discharge at all. It isn’t a quality issue, it is just whether the chemicals are compatible.