I've found that the line comes back if the item gets cold. I used the pen to mark on some linen for cross stitching motifs and when I put it in my car in the winter to take to work the lines started reappearing after I had ironed them off. Don't know if that would happen on cotton but it did on the Belfast linen.
Edit - ok I didn't read all the other posts that said the same thing. Sorry.
Last edited by Jamiestitcher62; 04-11-2014 at 07:16 AM.