Originally Posted by NJ Quilter

I think just about any marker that is permanent will do the trick for you. I'd look for a permanent marker with a tip size that you want and go from there. You could test on a piece of scrap fabric. I have a Sharpie brand (I think) that I've used in that fashion. To the best of my knowledge it's holding up fine through at least several washings. I just wrote on the back of the quilt as well.