Discharge printing is getting more and more popular as a way to produce soft prints on soft shirts. But it doesn’t always work.
The process is that the discharge agent in the ink combines with water and heat to neutralize the dye in the shirt. The color of the ink then goes into the fabric and there is no need for the usual underprint of white ink.
The problem is that it is tough to color match because until the shirt goes in the oven, it doesn’t look like much. The heated time in the dryer is required to finish the process. So you mix up the color, add the discharge agent (which only lasts one day or less), and then print it and send it down the dryer before you can see what you really are going to get. That is difficult enough, but in fact not all dyes are “dischargeable,” and it isn’t a quality issue. It just is a hand and glove type of thing where some work chemically and some don’t. So you have to try a shirt before you know if it will discharge.
You can print the shirt with a perfect ink mix and perfect technique and still it will not work if the shirt isn’t right. Only cotton dyes work, so that eliminates quite a few shirts, but beyond that you have to test.