Macor is the trademark for a machineable glass-ceramic developed and sold by Corning Inc. It is a white material that looks somewhat like porcelain. Macor is a good thermal insulator, and is stable up to temperatures of 1000 °C, with very little thermal expansion or outgassing. It can be machined into any shape using standard metalworking bits and tools.
- 46% silica (SiO2)
- 17% magnesium oxide (MgO)
- 16% aluminium oxide (Al2O3)
- 10% potassium (K2O)
- 7% boron (B2O3)
- 4% fluorine (F)
Macor has a density of 2.52 g/cm3, and a thermal conductivity of 1.46 W/(m·K). Its low-temperature (25 to 300 °C) thermal expansion is 9.3×10−6 m/(m·K). Its compressive strength is 50×103 lb/in2 (~350 MPa). Nominal engineering properties are comparable to borosilicate glass.
Macor comes in a standard size maxi slab (36x6cm approx.) Corning Macor Maxi-Slab. Components, bars, rods and plates can be machined within the size of this slab (hand tools can be used).