◆ A glasslike substance, enamel, is used to protect or decorate the surface of glass, metal and pottery. Also called porcelain enamel, it is made principally from borax, feldspar, lead, quartz and silica. Mineral oxides are added for coloring. These materials are all ground up into fine particles and then applied in various ways to whatever is being enameled. The article is then heated to about 1500 degrees Fahrenheit, which melts the enamel and unites it with whatever is being covered. The temperature at which the enamel melts must always be lower than that of the object being covered, otherwise the object would melt too.