Alumina Oxide is an intermediate oxide, and is used to stabilize fluxes and glass formers that compose glazes. It is calcined and ground to 325 mesh.
Melting point 2040°C
The use of too much alumina can cause a dry appearance in glazes, too little will allow the glaze to be overly runny. Lack of alumina in glazes can also result in glazes being soft and venerable to degradation from culinary acids. Its use in small amounts also prevents devitrification of glass. It is insoluble in water.