Just returned from a trip...I had taken along several blocks to be hand embroidered. They were a little rumpled from the travels, so I decided to press them before resuming my stitching. JUST as the iron hit the first block, I remembered the patterns were drawn with a Frixion pen.......oops....too late.....the unstitched design had disappeared....darn! Then I remembered reading on this board that the marks made with Frixions reappear if the pieces are exposed to cold temps......so I put my block in the freezer, and voila! The marks are a bit faded, but they are dark enough to guide my stitiching without having to remark the entire project!
Necessity....the mother of invention, indeed! Live and learn.