I have used micron pens and have seen the labels later and they seem to be ok. Sometimes I will use my ink-jet printer on the printable fabrics and they seem ok too. On these I have added a design from clipart or another place on line that mimicked one of the fabrics for example a giraffe when I had giraffe fabric in the quilt. As far as I know, they have remained but you got me to thinking with the gel pen story Peckish.