I use Pigma pens. I know a Sharpie will at least fade and possibly wash out of fabric over time. The key is probably how often you wash it. My son had bought a t-shirt at Camp this summer and had the band sign the back of it with Sharpies. I heat set it and have washed it probably once a week since the first of June! I can tell the names are starting to fade a bit. Barb C