I paint on glazed tile with china painting medium.  I fire the tiles in a kiln, the heat from the kiln softens the glaze on the tile so powder paint sinks into the glaze and makes it permanent. After the glaze they can be cleaned with products such as 409, Fantastic and Soft Scrub, without fear of damaging the surface. The only way you can hurt the painting after it has been fired, is by actually damaging the tile itself. You can also paint on sinks, floor tiles, and other porcelain or china products.
Specialty Custom Tiles
By Sandy Wassner