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. 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 Simax, Suprax, Kimax, Pyrex, Endural, Schott, or Refmex. 

More about Borosilicate Glass

Durable and heat resistant, borosilicate glass is the material of choice for a wide range of applications, from cookware to laboratory use. Typically referred to by one of its brand names, such as Pyrex or Schott, borosilicate glass consists of a silica, boric oxide, calcium oxide, sodium oxide and potassium oxide mixture, which varies slightly depending on the particular brand in question. Pyrex, which is the most common type of borosilicate glass, is produced by Corning Glass Works.

Creating borosilicate glass requires higher temperatures than those necessary for the production of regular glass, although this also accounts for its higher heat resistance. It also faces far less material stress than regular glass due to its lower thermal expansion coefficient, which also adds to its exceptional performance at high temperatures. Additionally, borosilicate glass is far more durable than traditional glass, and can withstand accidents that would break other glassware. Even when it does crack, it typically performs better, as it rarely shatters.

Borosilicate glass is perfect for scientific and medical laboratory use, since it offers excellent chemical resistance in addition to its other useful qualities. Everything from tubes, rods and beakers to test tubes, graduated cylinders, pipettes and stopper attachments are produced from borosilicate, and used in laboratories around the world. Although borosilicate glass offers exceptional acid resistance, it is less resistant to a range of alkalis, and occasionally other materials should be considered. Borosilicate glass is also used in certain optics, such as mirrors, because it retains shape well throughout changes in temperature. Other uses include the strengthening of various plastic compounds and in various gages and protective glass surfaces. 

The main distinction of borosilicate glass from traditional glass is the substitution of boron oxide for soda and lime in the manufacturing process. Borosilicate glass must contain at least five percent boron oxide, which helps bind the silicate and aluminum oxide and sodium oxide.