Originally Posted by
haylillan
i tested my pen by marking on 2 pcs of scrap i ironed 1 off and washed other off than ironed put both in freezer. the 1 I washed didn't come back. so the answer is dont iron your blocks until you've rinsed block just under running water
That alone is a good reason for me not to use them. I prefer to press my seams as I go and I certainly don't want to rinse every block and wait for it to dry (plus I don't always prewash and don't want partial shrinking). Even if I used it for quilting only, I always press my binding out before folding it over so that would be too much trouble for me to avoid pressing on marks.