Pyrex

Pyrex is a special kind of glass called borosilicate glass, first made by Corning Incorporated in 1908. It became well-known in 1915 as a brand of clear glass products that don’t break easily when heated or cooled. Because of these qualities, Pyrex is great for laboratory tools and kitchen items.

In the 1930s, Corning started making kitchen products from other kinds of glass besides borosilicate. In 1998, the company separated its kitchen product division, and now Pyrex dishes are made by Corelle Brands in the United States and International Cookware in Europe. Corning Incorporated still makes Pyrex glassware for science labs.

Remember, Pyrex is different from PUREX and is also not related to the programming language or rapper that share the same name.

History

Borosilicate glass was first created by a German chemist named Otto Schott in 1893. In 1908, a scientist at Corning Glass Works named Eugene Sullivan made a special type of glass called Nonex. This glass was strong and didn’t break easily, which was perfect for things like lantern globes.

Later, a Corning scientist named Jesse Littleton found that this glass could also be used for cooking. He gave his wife a small dish made from this glass, and it worked very well. In 1915, during World War I, Corning introduced Pyrex to the public. It was made without lead and became popular for kitchen items like pie pans. Over time, the company made many designs for Pyrex, working with different designers.

In 1998, Corning sold its kitchen products part of the business, and in 2019, the company that made Pyrex merged with another company. In 2025, the factory where Pyrex was made in Pennsylvania closed, and production moved to Ohio.

In Europe, a company called Arc International took over making Pyrex in 2006. They moved all production to France in 2007 from a factory in Sunderland, UK, which had been making Pyrex since 1922.

Trademark

Pyrex is still a trademark owned by Corning Incorporated, and it is allowed for use by two dinnerware makers.

Corning Incorporated keeps making PYREX (in all capital letters) lab glassware for markets around the world. The pyrex (in all lowercase letters, started in 1975) name is now used for kitchen items sold in the United States, South America, Asia, and Australia.

In Europe, Africa, and the Middle East, a version of the PYREX (all uppercase) trademark is used by International Cookware.

Composition

Older clear-glass Pyrex and Pyrex laboratory glassware are made of borosilicate glass. This type of glass contains boron, oxygen, sodium, aluminium, silicon, and potassium.

Starting around the 1950s, some Pyrex products began using soda–lime glass instead, which is easier to make and more affordable. This change means that Pyrex products made after this time might be made from different types of glass, which can affect how they handle heat.

According to the National Institute of Standards and Technology, borosilicate Pyrex is composed of (as percentage of weight): 4.0% boron, 54.0% oxygen, 2.8% sodium, 1.1% aluminium, 37.7% silicon, and 0.3% potassium.

According to glass supplier Pulles and Hannique, borosilicate Pyrex is made of Corning 7740 glass and is equivalent in formulation to Schott Glass 8330 glass sold under the "Duran" brand name. The composition of both Corning 7740 and Schott 8330 is given as 80.6% SiO₂, 12.6% B₂O₃, 4.2% Na₂O, 2.2% Al₂O₃, 0.1% CaO, 0.1% Cl, 0.05% MgO, and 0.04% Fe₂O₃.

Patterns and collecting

Pyrex has become popular among collectors because of its different colors and designs made after World War II. Some special patterns, like the 1956 Pink Daisy or the 1983 Colonial Mist, can be very valuable. Prices for single pieces can be around $100, and some collections can reach $500. Rare or special pieces have sometimes sold for much more on eBay.

Use in telescopes

Because of its special properties, borosilicate glass is often used for mirrors in telescopes.

In 1932, George Ellery Hale asked Corning to make the 200-inch telescope mirror for the Palomar Observatory project. Earlier attempts with fused quartz failed. Corning made the mirror from borosilicate glass between 1934 and 1936. After a long cooling process, the mirror was finished in 1935. The first mirror is now kept at the Corning Museum of Glass.