What Is Thermal Shock Resistant Borosilicate Glass?

Borosilicate shock-resistant glass is better known by the trade name Pyrex.

Shock-resistant borosilicate glass is more commonly known by its trademarked name, Pyrex. Using silica (or silicon dioxide) and boron oxide as the main ingredients, borosilicate glass has special properties making it useful for cooking, laboratory work and industrial processes. What makes borosilicate glass special is that it will not fracture when exposed to extreme quick temperature changes. This means the borosilicate glass can go from the freezer to the frying pan without fear of the glass shattering. Normal window glass has a much lower temperature tolerance and can easily break if exposed to rapid temperature changes.

History

Borosilicate glass was the result of the work of German chemist Otto Schott. According to the Schott Corporation's biography of the company's founder, Otto Schott was looking for a way to heat materials in the laboratory without facing imminent fracture of test tubes and beakers. He experimented with different combinations of materials until he arrived at borosilicate glass.

Pyrex

In 1915 the American Corning Company bought the rights to Schott's work and marketed it as Pyrex. Pyrex could be used in a variety of applications, including consumer use in the kitchen. Pyrex's popularity caught on and has been a mainstay in American kitchens.

Ceramic

Although having similar properties, borosilicate glass is not a ceramic material. Ceramics are defined has being made of nonmetallic solids. Boron and silicone are both classified as metals, and borosilicate is a glass. Pyrex and other products made of borosilicate glass are often mistaken for ceramics because they are not necessarily transparent. Whether transparent or opaque, however, is not the determining factor in borosilicate glass production.

Other Glass

In the years' since Schott's work, other materials are also used to make shock-resistant glass. Glass tempering (raising and cooling the temperature during production) can lead to shock-resistant properties with more common soda and lime glass. Also, as the patent for the original borosilicate glass has expired, other manufacturers market shock-resistant borosilicate glass as Bomex, Duran and Kimax.

Limitations

When using borosilicate glass in different applications, it is important to remember that it does have limitations. "Shock resistant" is not the same as "shock proof." When using borosilicate glass, avoid temperature changes of more than 150 degrees Fahrenheit. Also, "rapid" means a process of possibly taking a Pyrex dish from a hot oven and immediately submerging it in cold water. The transition from the oven to room temperature will not affect the borosilicate glass. The same is true of taking a dish from the freezer and placing it in an oven to warm. The shock value of these uses would not lead to a fracture.

References

• Schott: Corporate History
• Consumer Affairs: Three Years Later: Pyrex Dishes Still Go Boom