There are many advantages to glass–ceramics that are derived from internal nucleation and crystallization of bulk glass articles. Rapid commercial glass forming processes like rolling, pressing and casting may be used. A simple reheating process suffices to achieve a fine-grained and uniform microstructure with little or no porosity. The shape of the original glass article is preserved even as a high degree of crystallinity develops.
Glass–ceramics may be considered as refractory if they can be used at temperatures above 1200 °C. The most interesting of these are based on alkaline earth aluminosilicate compositions in the RO–Al2O3–SiO2–TiO2 system, where R is primarily Mg, Sr or Ba, and TiO2 is the nucleating agent. In these glass–ceramics a combination of good flexural strength, hardness, fracture toughness, and resistance to both high temperature and thermal shock can be produced.