My friend Cindi, in preparation for a signature quilt, did an experiment and tested all of the permanent markers she could get her hands on, including Sharpie, PrismaColor, Micron, and Nano-Liner. She ran samples through all kinds of laundry hoops and the clear winner was the Nano-Liner by Royal Langnickel. It was the only pen that didn't run and didn't fade. She found them at Hobby Lobby.