Barkeeper's Friend, Preferred Mule Mug Polishing Agent

Barkeeper's Friend is a cleanser and polish for fiberglass, stainless steel, glass cooktops, copper, tile, and brass. DIRECTIONS: Sprinkle BKF on a thoroughly wet cloth and rub gently. If applying BKF directly to metal, porcelain or plastic, make certain surface is wet then rub gently until rust or discoloration disappears. Rinse. IMPORTANT: We do not recommend cleaning the interior of a copper mug.