I have used the Frixon pens for marking quilting lines. I am careful to stitch right on the marked lines. When I can, I use a color ink to match the thread. When I'm done quilting over the lines, I use a Blow Dryer vs an iron to erase the ink. To me its better as I'm not stretching the fabric with an iron. So far I haven't had any lines reappear. It doesn't get very cold where I live.