I know that many quilters say you should not use Frixion pens; but I use the black fine line ones by the dozens. I use the fine line as that is the only kind my office supply sells. I just finished using a Frixion pen to mark the quilting design on a quilt. It will be a quilt that will be well used. If the lines come back, heat will remove them again. If there is some chemical in the ink that will ultimately damage the quilt, that is OK. I am not making the quilt to, one day, be a beloved antique.