Borosilicate glass

Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), making them resistant to thermal shock, more so than any other common glass. Such glass is less subject to thermal stress and is commonly used for the construction of reagent bottles. Borosilicate glass is sold under such trade names as Borcam, Borosil, DURAN, Pyrex, Supertek®, Suprax, Simax, BSA 60, BSC 51 (By NIPRO), Heatex, Endural, Schott, Refmex, Kimble, MG(India) and some (but not all) items sold under different trade names. Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), making them resistant to thermal shock, more so than any other common glass. Such glass is less subject to thermal stress and is commonly used for the construction of reagent bottles. Borosilicate glass is sold under such trade names as Borcam, Borosil, DURAN, Pyrex, Supertek®, Suprax, Simax, BSA 60, BSC 51 (By NIPRO), Heatex, Endural, Schott, Refmex, Kimble, MG(India) and some (but not all) items sold under different trade names. Borosilicate glass was first developed by the German glassmaker Otto Schott in the late 19th century. Otto Schott was also the founder of today's Schott AG, which has sold borosilicate glass later under the brand name DURAN. As part of an equity carve-out in 2005, the DURAN Group was founded and the manufacture of Duran was transferred to it. After Corning Glass Works introduced Pyrex in 1915, the name became synonymous for borosilicate glass in the English-speaking world (though, in reality, a sizable portion of the glass produced under the Pyrex brand has also been made of soda-lime glass since the 1940s). However, borosilicate glass is the name of a glass family with various members tailored to completely different purposes. Most common today is borosilicate 3.3 glass such as Duran, International Cookware's NIPRO BSA 60, and BSC 51. In addition to quartz, sodium carbonate, and aluminium 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% aluminium 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 use in chemical laboratory equipment, cookware, lighting, and in certain kinds of windows. Borosilicate glass is created by combining and melting boric oxide, silica sand, soda ash, and alumina. Since borosilicate glass melts at a higher temperature than ordinary silicate glass, some new techniques were required for industrial production. The manufacturing process depends on the product geometry and can be differentiated between different methods like floating, tube drawing, or moulding. The common type of borosilicate glass used for laboratory glassware has a very low thermal expansion coefficient (3.3 × 10−6 K−1), about one-third that of ordinary soda-lime glass. This reduces material stresses caused by temperature gradients, which makes borosilicate a more suitable type of glass for certain applications (see below). Fused quartzware is even better in this respect (having one-fifteenth the thermal expansion of soda-lime glass); however, the difficulty of working with fused quartz makes quartzware much more expensive, and borosilicate glass is a low-cost compromise. While more resistant to thermal shock than other types of glass, borosilicate glass can still crack or shatter when subjected to rapid or uneven temperature variations.