I've used cheapie sweatshirts with Crayola fabric crayons. I'm sure they are not 100% cotton. My kids wrote a letter to Grandma with magic marker on paper. We flipped the paper, taped it to a window and let them trace the reverse with the crayons. I ironed the crayon from the paper to the sweatshirt. This was when my daughter was in kindergarden. She turns 21 next month and I've see her Grandma wear the sweatshirt as recently as last winter. It still looks pretty good considering its age.