Home Depot Informative - Thermocast Sink Stains
As I've found out Thermocast sinks (Black) stain easily when dish water or a pan is left in the sink overnight. The black finish turns a gray color and doesn't wash away. The manufacture recommends from the start of installation that the sink be washed and waxed on a regular schedule. Fine, I flobbed up. Anyway my fix for the stain works for me and I'm very happy with the results: From MCMASTER. COM purchase a quart can of DYKEM Remover & Cleaner, and a half pint can of DYKEM Staining Color Black. Clean sink with mild soap and water, rinse, and let dry completely. Wipe down the bottom of the sink with the DYKEM cleaner and let dry. Coat the bottom of the sink with the DYKEM Stain and let dry. When stain dries wipe (Buff) with dry cloth to remove any high spots of uneven Stain. Last apply two coats of Dupont Teflon Car Wax and buff to shine. It's been two months and the sink still looks great, not new but very close. Good Luck.