A few days back someone talked about the Fri X ion pens. It was said that the markings could eliminated by heating, but that they would reappear when the fabric was placed in a cold environment. Well that got me to thinking. I purchased the pens (black, blue, red) and used these pens to write their own colors on a piece of 100% pink fabric. I then ironed the fabric and sure enough, the lettering disappeared. I then stuck the piece of fabric in the freezer and sure enough, the lettering returned. I then reheated, lettering gone and then I put the piece of fabric in the washing machine and cycled it with other clothes. I then put the fabric BACK into the freezer and NO lettering reappeared. Hope this helps.