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Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915. According to Carroll Gantz, Dr. Jesse Littleton of Corning discovered its cooking potential by presenting his wife with a makeshift casserole made from a cut down Nonex (a low expansion glass developed in 1908 by Dr. Eugene Sullivan) battery jar. Corning then removed the lead that was present at the time, and Pyrex was born.

Originally, Pyrex was made from thermal shock resistant borosilicate glass. In 1998, Corning sold its consumer products division which subsequently adopted the name World Kitchen. Pyrex kitchen glassware manufactured and licensed for sale in the United States is now made of tempered soda lime glass at the World Kitchen facility in Charleroi, Pennsylvaniamarker. Pyrex products for the European Union continue to be made of borosilicate glass in France. Pyrex laboratory glassware is also still made of borosilicate glass.

History of the Pyrex Brand

Though borosilicates had been produced before the Pyrex brand, the name Pyrex is widely used as a genericized trademark for the material. Corning sold off its Consumer Products division in 1998 as World Kitchen but retained the Pyrex brand name, licensing it to World Kitchen and other companies that produce Pyrex-branded cookware (e.g. Newell Rubbermaid's Newell Cookware Europe).The brand in Europe, the Middle East and Africa is currently owned by ARC International who acquired the European business in early 2006 from Newell Rubbermaid who in turn had acquired it from Corning in the 1990s.

A Corning executive gave the following account of the etymology of the Pyrex brand name:

Pyrex kitchen products in Europe made and sold by a subsidiary of ARC International tableware company are made from borosilicate glass.


In 1948 an internal design department was started by John B. Ward. He redesigned the Pyrex ovenware and Flameware. Over the years designers such as Penny Sparke, Betty Baugh, Smart Design, TEAMS Design, and others have contributed to the design of the line.


Except for the Charleroi, PA-made Pyrex glass cookware, older Pyrex and European Pyrex is still made of borosilicate glass. According to the National Institute of Standards and Technology, borosilicate Pyrex is composed of (as percentage of weight): 4% boron, 54% oxygen, 3% sodium, 1% aluminium, 38% silicon, and less than 1% potassium.

According to glass supplier Pulles and Hannique, borosilicate Pyrex is made of Corning 7740 glass, and is equivalent in formulation to Schott Glass 8830 glass sold under the "Duran" brand name. The composition of both Corning 7740 and Schott 8830 is given as 80.6% SiO2, 12.6% B2O3, 4.2% Na2O, 2.2%Al2O3, 0.04% Fe2O3, 0.1% CaO, 0.05% MgO, and 0.1% Cl.

Use in laboratory ware

Because Pyrex borosilicate glass has a high thermal resistance it is often used in the manufacture of laboratory ware. In Europe, SciLabware Limited manufacture more than 800 items under the Pyrex brand name including beakers, bottles, flasks, dishes and test tubes.

Usage in telescopes

Because of its low expansion characteristics, Pyrex is often the material of choice for reflective optics in astronomy applications. The California Institute of Technologymarker's telescope mirror at Palomar Observatorymarker was cast by Corning during 1934–1936 out of borosilicate glass.

In 1932, George Ellery Hale approached Corning with the challenge of fabricating the required optic for his Palomar project. A previous effort to fabricate the optic from fused quartz had failed.

Corning's first attempt was a failure, the cast blank having voids. Using lessons learned, Corning was successful in the casting of the second blank. After a year of cooling, during which it was almost lost to a flood, in 1935 the blank was completed. The first blank now resides in Corning's Museum of Glass.marker

The University of Arizonamarker is currently engaged in the fabrication of seven 8.4 meter optical blanks for its Giant Magellan Telescopemarker using borosilicate glass.


In May 2008, in a report broadcast on a Chicago TV channel, Pam Zekman reported that people have complained that Pyrex bakeware has shattered or even exploded during ordinary use. US Senator Dick Durbin and US Congresswoman Jan Schakowsky from Illinois have called on the Consumer Product Safety Commission to find out if there is a problem with Pyrex. Zekman's segment did not include any reports on actual laboratory tests of Pyrex glassware. The segment went on to say that none of the US hospital emergency rooms surveyed by the Consumer Product Safety Commission reported treating any injuries in 2005 or 2006 that were due to breakage of Pyrex glassware. The CPSC has nonetheless received a number of reports of failures directly from consumers. The company has a web page devoted to these and other consumer issues.


  1. Pyrex History
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  7. Exploding Pyrex at


  • Gantz, Carroll, (2005). DESIGN CHRONICLES: Significant Mass-produced Products of the 20th Century, Schiffer Publishing, ISBN 978-0764322235

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