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Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion(~3 × 10−6 /°C at 20°C), making them resistant to thermal shock, more so than any other common glass.

In addition to the quartz, sodium carbonate, and aluminum oxide traditionally used in glassmaking, boron is used in the manufacture of borosilicate glass. The composition of low expansion borosilicate glass such as those laboratory glasses mentioned above is approximately 80% silica, 13% boric oxide, 4% sodium oxide, and 2-3% aluminum oxide. Though more difficult to make than traditional glass due to the high melting temperature required, it is economical to produce. Its superior durability, chemical and heat resistance finds excellent use in chemical laboratory equipment, cookware, lighting and, in certain cases, windows.