Recently I was working on some tricky curved seam patchwork that had to be manuevered and ripped out several times before I was happy with it. Unfortunately the color of the yellow-green piece rubbed off onto the light blue patch from all the handling, I guess! I hadn't prewashed the yellow green batik, but decided to go do that before I cut another piece, but when I did no color was released into the water! I did use Best Press on the patches, maybe that's what caused it???? I have had colors run before, but only when the fabric was washed, not while I was sewing!