Thank you so much for your "homework" on Frixion pens. According to some quilt teachers on You Tube, the Frixion pens are the best thing ever. I have purchased a couple Frixion pens in different colors, so now I'm not sure if I will use them on my fabric in the future for marking lines. I will be careful how I use them in the future and I thank you for your research and sharing it on QB. Happy quilting.