Zinc Oxide – ZnO (m.p. 3272o F/1800o C) an important component of many glaze types (cone 5-13) and is used as a flux, opacifier, and color modifier. It reduces the expansion of a glaze (second only to Magnesia), improves craze resistance, gloss, whiteness, and increases maturing range. In crystalline glazes, low in Alumina, it promotes crystal growth.