Copper Oxide Black – CO₂O₄CoO (m.p. 2100^o F/1149^o C) – a common form of copper in glazes (2%-5%). It is a strong flux used as a colorant to produce greens in oxidation and reds in reduction. Other colors are turquoise in Soda based glazes, yellow-greens in Potash, and blue-greens in Barium. Copper Carbonate can be substituted for Oxide if the amount is doubled.