that fabric tac is permanant, I hope you haven't done but one square with it. I've ironed the blue pen and not had trouble but you never know! I use freezer paper, cut to size and iron on top of my fabric, it's easy to turn under and sew then peels off easily when you're done. Are you by any chance doing a little quilt that looks like ceramic tiles and has some flowers appliqued on top of them? If you use glue, be sure it's washable school glue, try not to get it on the part you're stitching because it too is a little hard to stitch thru. good luck