Enamel

Enamel, vitreous (glasslike) glaze fused on metal for decoration and protection. Silica, potassium carbonate, borax, and trilead tetroxide are fused to form a glass (called flux) which is colored by metal oxides; tin oxide makes it opaque. The enamel is powdered and spread over the cleaned metal object, which is then fired in a furnace until the enamel melts.