I use the pens quite a bit with great success ...but.....when marking on dark fabrics, it may leave a faint line....stitching will cover it, but if you mark by mistake, you will have that faint line.....washing the fabrics with detergent seems to make the lines disappear a bit more....I don't worry about the lines coming back by being subjected to cold....it takes quite a bit of cold for them to reappear....like putting a quilt in the freezer for a couple hours.....who does that?....all you have to do is throw it in the dryer and they are gone again anyway.....I've tried this, so I know.....you must always test the markers on a piece of scrap before marking your quilt top, the same as any other marking system....better safe than sorry...
