I use the Crayola Ultra Washable markers, tested them with ironing and they all washed out. Here's the thread with the test and results. Bear in mind this was on 100% cotton. If you're using other fibers, test first. 10 minutes worth of testing on a swatch of fabric is worth it, compared to ruining hours upon hours of work, not to mention the $$ invested in your fabrics.
http://www.quiltingboard.com/main-f1...s-t283729.html