I have put the fact that the line reappears in cold to good use.... discovered by accident! I had traced an intricate embroidery design onto my fabric with the friction pen. Then I ironed a stabiliser to the back of my fabric. Oh no! my whole design was erased. Because I had heard that cold makes the line reappear, I decided to put my piece in the freezer. A couple of hours later, my design was back. Now I use this method every time I trace an embroidery design. I use the frixon pens for other markings too...really like them.