Copper carbonate (CuCO3) is a green powder that is mainly used as a glaze or as a coating for liquid clay. Depending on the conditions of burning and the formulation of the glass, it can produce shades of green, turquoise, or red (red usually occurs in reduced combustion). Copper carbonate by brushing can also be used as a scrubber in cookie cutters. Suggested concentrations of copper in the vitreous setting are as follows: In liquid slurry: 2-8% In glass: 5% If concentrations above 5% are used, the glass will often turn to metallic pewter. Important information: Copper should not be used as an ingredient in soluble glass that will come into contact with food or drink, as it is likely to leak. In powder form, copper carbonate is harmful if swallowed, and may cause skin and eye irritation on contact. Please use protective caps when handling this chemical.