Pyrex

thumb|A PYREX 1-[[quart measuring cup manufactured after 1940, featuring graduations in United States customary units]]

Pyrex (trademarked as PYREX and pyrex) is a type of borosilicate glass developed by Corning Incorporated in 1908. Pyrex was first introduced to the public in 1915, as a brand of clear, low-thermal-expansion glassware products, whose resistance to chemicals, electricity, and heat made it ideal for laboratory glassware and kitchenware. In the 1930s, Corning expanded the brand to include kitchen products made of soda–lime glass and other materials.

In 1998, Corning Incorporated spun off its kitchenware division, including Pyrex cookware. Currently, Pyrex dishes are manufactured by Corelle Brands in the United States and International Cookware in Europe. Corning Incorporated continues to manufacture Pyrex scientific glassware.

History

Corning Glass Works

thumb|upright|alt=A black and white advert for Pyrex entitled "You Really Can't Get Along Without This Pyrex Biscuit Dish".|1915 Pyrex advertisement

Borosilicate glass was first made by German chemist and glass technologist Otto Schott, founder of Schott AG in 1893.

In 1908, Eugene Sullivan, director of research at Corning Glass Works, developed Nonex, a borosilicate low-expansion glass, to reduce breakage in shock-resistant lantern globes and battery jars. Sullivan had learned about Schott's borosilicate glass as a doctoral student in Leipzig, Germany.

thumb|left|A series of Pyrex [[Erlenmeyer flasks]]

Jesse Littleton of Corning discovered the cooking potential of borosilicate glass by giving his wife Bessie Littleton a casserole dish made from a cut-down Nonex battery jar. Corning removed the lead from Nonex and developed it as a consumer product. A Corning executive gave the following account of the etymology of the name "Pyrex":Corning purchased the Macbeth-Evans Glass Company in 1936 and their Charleroi, Pennsylvania plant was used to produce Pyrex opal ware bowls and bakeware made of tempered soda–lime glass. In 1958 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.

alt=A 2-cup pyrex measuring jug manufactured by Corelle.|thumb|A 2-cup pyrex measuring jug manufactured by Corelle.

Corelle Brands

In 1998 Corning Incorporated divested itself of its consumer products division, which was renamed World Kitchen in 2000, and Corelle Brands in 2018. Corelle took over production of Pyrex and other Corningware products in the United States.

In 2019 Corelle Brands merged with Instant Brands, the makers of the Instant Pot. The combined company filed for Chapter 11 bankruptcy in 2023 after high interest rates and waning access to credit hit its cash position and made its debts unsustainable. The company emerged from bankruptcy after the appliance portion (Instant Brands) and the housewares portion (Corelle Brands) of the business were separately purchased by private equity firm Centre Lane Partners, one of the largest stockholders in Pyrex rival Anchor Hocking.

After the purchase was finalized in early 2024, Centre Lane transferred ownership of Corelle to Anchor Hocking. This arrangement came into public awareness later in the year after Anchor Hocking announced that they planned to close Pyrex's 132-year old factory in Charleroi, Pennsylvania, and relocate production to Anchor Hocking's factory in Lancaster, Ohio. Senators Bob Casey Jr. and John Fetterman each criticized the move and demanded an explanation for how the merger of two major competitors was able to proceed without Federal Trade Commission oversight.

A lawsuit by the State of Pennsylvania against Centre Lane Partners that attempted to halt the factory closure was dismissed by a federal judge.

European history

After Corning Incorporated divested itself of its consumer products division in 1998, Newell Cookware Europe retained its license to produce Pyrex in Europe, Africa, and the Middle East.

France-based cookware maker Arc International acquired Newell's European business in early 2006 to own rights to the brand in Europe, the Middle East and Africa. In 2007, Arc closed the Pyrex soda–lime factory in Sunderland, UK moving all European production to France. The Sunderland factory had first started making Pyrex in 1922.

Arc International sold off its Arc International Cookware division including Pyrex business in 2014, and the division was subsequently renamed the International Cookware group. London-based private equity firm Kartesia purchased International Cookware in 2020.

In 2021, International Cookware acquired Pyrex rival Duralex for €3.5 million (US$4.2m).

Trademark

Pyrex remains a trademark of Corning Incorporated, but is licensed by two dinnerware manufacturers.

thumb|Pyrex logo as used by Corelle

Corning Incorporated continues to manufacture PYREX (all uppercase) laboratory glassware for international markets.) trademark is now used for kitchenware sold in the United States, South America, Asia, and Australia.

Composition

thumb|right|alt=Two clear measuring jugs featuring red text. The jug on the right is wider than the jug on the left.| A clear tempered pyrex soda–lime glass measuring jug produced by Instant Brands (left, differentiated by its different logo and bluish tint), and a clear borosilicate glass PYREX measuring jug produced by Corning (right)

Older clear-glass Pyrex manufactured by Corning, International Cookware's Pyrex products, and Pyrex laboratory glassware are made of borosilicate glass. 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% , 12.6% , 4.2% , 2.2% , 0.1% , 0.1% , 0.05% , and 0.04% .

Starting around the 1950s, Corning began making Pyrex out of thermally tempered soda–lime glass, instead of borosilicate glass, due to lower manufacturing costs. Some plants moved to tempered soda–lime formulations, while others continued to produce borosilicate Pyrex. Herb Dann, a designer at Corning from 1961 to the 1990s, noted that by the time the consumer products division was sold in 1998, Corning had mostly switched to soda–lime glass for "almost all" of its tableware products. This change was justified by stating that soda–lime glass has higher mechanical strength than borosilicateit has around twice the strengthmaking it more resistant to physical damage when dropped, which is believed to be the most common cause of breakage in glass bakeware. However, its thermal shock resistance is lower than borosilicate's, leading to potential breakage from heat stress if used contrary to recommendations.

{|class="wikitable"

|+Calculations of thermal differential, ∆T, for soda lime silicate and borosilicate glass.

!Source

!∆T Soda lime silicate

!∆T Pyrex borosilicate

|Bradt and Martens

|~80°C (144°F)

|~270°C (436°F)

|Corning brochure

|~16°C (29°F)

|~54°C (97°F)

</div>

The differences between Pyrex-branded glass products has also led to controversy regarding safety issuesin 2008, the U.S. Consumer Product Safety Commission reported it had received 66 complaints by users reporting that their Pyrex glassware had shattered over the prior ten years yet concluded that Pyrex glass bakeware does not present a safety concern. The consumer affairs magazine Consumer Reports investigated the issue and released test results, in January 2011, confirming that borosilicate glass bakeware was less susceptible to thermal shock breakage than tempered soda lime bakeware. They admitted their testing conditions were "contrary to instructions" provided by the manufacturer. STATS analyzed the data available and found that the most common way that users were injured by glassware was via mechanical breakage, being hit or dropped, and that "the change to soda lime represents a greater net safety benefit."

Distinguishing soda–lime and borosilicate Pyrex

It is a common misconception that the logo style alone indicates the type of glass used to manufacture the bakeware. In reality, Corning's introduction of soda–lime based Pyrex in the 1940s predates the introduction of the all lowercase logo by around 30 years, which first appeared in 1975. The U.S. Pyrex website notes: "You may notice that some of our Pyrex® brand glassware has a slight tint of green or blue hue to the dish. It is not a coating or added color. It comes from the raw materials in the glass itself. The blue comes from adding cobalt to the raw materials. This does not affect the performance of the dish; it is purely cosmetic."

U.S. post–1998

From 1998, World Kitchen (Later Corelle Brands, then Anchor Hocking) used the Corning soda–lime formulation at their plant in Charleroi, Pennsylvania. Production was then shifted to Lancaster, Ohio by new owners Anchor Hocking. Ultimately, production of all U.S. Pyrex since 1998 has been made of soda–lime glass with the lowercase logo.

England

In 1921, James A Jobling acquired the licence to produce Pyrex in the UK. The original kiln was replaced with a borosilicate furnace to create the Pyrex. Production started in 1922 at his Sunderland factory in England, and continued for over 50 years. In 1973, the licence expired, and Corning took control of the factory and the Jobling company. Pyrex produced before Corning took over was stamped with a "JAJ" symbol. Production at the facility took place until 2007 when it was shut down, and production of Pyrex was shifted to France. All Pyrex made at the factory was borosilicate. All Pyrex made at the factory is borosilicate with the uppercase logo. However, they also offer the French-made borosilicate glass. Additionally, borosilicate glass with the lowercase logo is offered in the "Bake N Serve" and "Cook N Serve" ranges which are produced in China.

Previously, Pyrex was produced in Australia by Crown Crystal Glass from 1926. Many pieces were labelled with various stamps, or lacking stamps entirely. through its various colours and patterns produced after World War II, lending itself to collectors. Some valuable patterns include the 1956 Pink Daisy or the 1983 Colonial Mist. Uncommon shapes or limited-run productions also affect the value of the pieces. A previous effort to fabricate the optic from fused quartz had failed, with the cast blank having voids. The mirror was cast by Corning during 1934–1936 out of borosilicate glass. After a year of cooling, during which it was almost lost to a flood, the blank was completed in 1935. The first blank now resides in the Corning Museum of Glass.

Gallery

File:Chocolate cake and ice cream.jpg|A Pyrex plate manufactured in the 1960s

File:Pyrex dish.jpg|A vintage Pyrex roaster

File:Pyrexette Kit.jpg|A 1925 Pyrex glass baking dish set for children

File:Museum of Glass Pyrex exhibit - panoramio.jpg|Pyrex exhibit in the Corning Museum of Glass