A couple of years ago, I gave the markers a try through an experiment. I took yellow T shirts and drew a detailed logo on the back of each with the black marker filling in the spaces. The design was as large as a piece of paper. After we used the shirts once for a skit, I washed them with no special treatment. Poof all the black was gone...not a smidgen of color showed. My biggest regret....I didn't save the design...it was a clever idea if I do say so myself.
I did wash the shirts before coloring.