These pens are fine to use for marking fabric for me. Many quilt bloggers have tested and retested them. One blogger, a chemist, tested the pens on fabric with starch, no starch, washed, ironed, and frozen. I forgot all the results but the chemical analysis showed the pens do not harm cotton fabric. Quilt bloggers are in the thousands online and one bad product, the news travels in seconds to millions of followers. Same with a great new product.