Macor is a machineable glass-ceramic eveloped and sold by Corning Incorporated It is a white material that looks somewhat like porcelain. Macor has excellent thermal characteristics, acting as efficient insulation, and stable up to temperatures of 1000 °C, with very little thermal expansion or outgassing. It can be machined into any desired shape using standard metalworking bits and tools. This combination of machinability and good thermal properties have made it the material of choice in many engineering contexts.