Not all 100% cotton garments are right for use with discharge ink. Many people don’t know that when some manufactures are dying their garments, they can sometimes make major mistakes. When a garment manufacturer is dying a lot of shirts that should be the cherry red but instead come out prune purple they will often over-dye those shirts with black dye in an effort to save them from being totally wasted. While this is a great way of saving money for the manufacturer, it could be a quick way for a printer to lose money.
When over-dyed shirts are discharged it is not uncommon to see a tie-dye effect when the ink is cured. This usually happens when the ink has not saturated the garment enough to remove the double layer of dye that the garment holds. The easy way to avoid this is to ask your garment supplier to make sure you are not getting over-dyed blank apparel if you are doing a discharge print.
It is also a good idea to make sure that there are not trace amounts of poly or other fibers in shirts that you are going to discharge. Flecks of dark colored poly will actually bleed during curing and can leave you with a spotted image on your shirt.