The basic composition of enamel is quartz, feldspar, borax and fluoride, belonging to silicate material, the same with ceramic glaze, liuli (similar with azure stone) and glass. In ancient China, this matter attached to the surface of pottery or inserter was habitually in the calling of ceramic glaze, attached to the surface of tile pieces for building was in the calling of liuli. But attached to the surface of the metals then be called "enamel".