$ store 2 cup soup mug and medium plate. Used Sharpie Paint Oil Based. Put in cold oven, right after painting baked at 300 for 45 min from putting in. Took out when cool enough to touch comfortably. Used the royal blue and it turned a lovely turquiose. Red paint pen turns ruby, yellow stays yellow, but turns a bit darker. White turns off-white. Black scrapes off, so will not use that. The other colors are stable. Set has gone through several washings with no sign of scraping off.