My take on the Frixion pens: I used some on a small wall hanging I was doing for a guild challenge and was later going to give to my in-laws. Used blue to mark quilting lines on a white background and red to mark quilting lines on a solid black border. The blue ironed out just fine, but the red left a slight silvery line on the black that I couldn't remove by any means, but I decided it would be OK on this project. When we journeyed to my in-laws, we drove at night and napped in a restaurant parking lot for a couple hours waiting for them to open for breakfast. Apparently it got rather cool in the car (northern PA in February), as when I pulled out my masterpiece to present it to them, there were blue lines all over the white background! I was able to iron them out again, but it kind of ruined the presentation. I will NOT be using the pens again for marking material.