Bowls may become stained throughout regular use and transport. Keep your bowl extra clean with distilled water and mild dishwashing soap. Use a soft hand cloth to do any kind of cleaning. No steel wool/metal, as that will scratch or damage the patina. Frosted bowls with stains may benefit from a steam cleaning as cloth can become lodged in the rough exterior. A small handheld steam cleaner can be used to blast the surface clean. No matter what you use, always rinse your bowl with clean water and dry with a hair dryer or let air dry while it sits upside down on dry towel.