I researched the Frixion pens at Amazon -- provides more info about them. The marks are removed with heat but reappear with cold (as in freezer type cold). Someone posted in a different thread (search here on Frixion) that the marks reappear with cold even after the quilt has been washed, which suggests that the chemicals used in the pen stay in the fabric. No one knows if, with time, those chemicals may affect the fabric or the dyes in the fabric. That's why I would hesitate to use them in a quilt I would want to last for a very long time.