Cupric Oxide in Ceramic Formulations 

Copper Oxide is one of the earliest colorants used by potters. As previously described, it is used to produce a blue gray in a 50% mixture with frit, a green color in oxidizing firings up to 5% where it moves toward black, and a vibrant red color in reduction firings. It can be used as a wash and as a brushed-on application on bisqueware. It is used with enamel frits to increase the adherence of glazes. When used as a flux it can decrease the melting temperature required to increase the fluidity in the melt of the glaze. 

Cupric Oxide in Fireworks and Pyrotechnics 

Other than the aforementioned use to produce a moderate blue color it can be used as a flash powder oxidizer because of its fast reaction with magnesium, aluminum, or a combination of the two, magnalium powder. When used in a thermite reaction it reacts quickly to form large amounts of molten copper metal that is known to send out droplets of molten metal and should be treated with extreme caution. This is used for welding thick copper wires in electrical connections. It is sometimes used in fireworks to produce a strobe or crackling stars effect.