I use a lot of batik (usually brand name ones), but I don't prewash the precuts. When my quilt is done, I wash it with a few color catchers and have never had a problem. I do prewash the yardage though, also with color catchers. Mostly the color catchers come out with very little color on them - maybe it's due to the quality of the fabric? I generally buy the major brand names. I find that I get more color on them from greens/yellows than I do purples/reds/blues. That surprised me.