So there are Frixion pens that do work and don't work...as in are for paper only? I'm just catching on to these pens. Can someone tell me what kinds there are and which ones not to use on fabric? I'm thinking of using them on quilts for my grandkids, etc. that will be used all the time and will probably never become heirlooms, so who cares about what the marks will do 30 yrs. from now. (I hope the quilts are loved to death by then.) Are Frixion pens erasable pens? Someone mentioned highlighters too. I'm getting from different posts that Frixion makes a variety of pens and I thought there was only one, but then I haven't shopped for them either. What do I buy to mark light fabrics and dark fabrics?