Toy Borracha Dominican Magic Mug . It appears black when cold, but reveals the artwork when exposed to hot liquids. • Ceramic • Black glossy finish when cold • Reveals the print when exposed to hot liquids • Dimensions: height - 3.54'' (8.9 cm), diameter - 3.35" (8.5 cm) Note that in some instances the coating might not be 100% opaque and an outline of the design might peek through a little. You shouldn't put mugs in a microwave or dishwasher since it can damage the coating.