The Pyrex Glass Controversy That Just Won't Die

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The Pyrex Glass Controversy That Just Won't Die

Adam Clark Estes
Saturday 11:00am

Clear glass Pyrex cookware is practically an American icon. With its pleasing heft and remarkable resilience, these famous clear pans have been essential when cooking biscuits, casseroles, and pies since 1915. There’s only one problem. A few years ago, the pans started exploding when they got too hot—which is ironic since Pyrex glass was specifically designed to be heat resistant. Some blamed a change in the glass formula and flocked to thrift stores to buy older models. Others cried hoax. Everyone agrees that exploding glass is bad.

Pyrex made headlines recently, because its parent company made a big move. Corelle Brands, parent company of Pyrex among others, is planning to merge with Instant Brands, maker of the very popular Instant Pot. Terms of deal were not disclosed, and it’s unclear how the merger will affect any of the companies’ products. However, the news does bring to mind that decades-old controversy involving beloved glass pans, violent explosions, and some gnarly injuries. Pyrex is also the subject of a class action lawsuit in Illinois. In court filings, Pyrex’s parent company, Corelle Brands, insists that incidents of breakage result from customers improperly using their products. More on that case in a minute.

To understand the Pyrex controversy, you have to look at the reports of explosions within the context of the history of glass. Not the whole history of glass, of course, but rather a series of innovations that started with Otto Schott, a German scientist who invented a new type of glass in the late 1800s. This so-called borosilicate glass was not only heat resistant but also stood up to sudden temperature changes. Corning Glass Works developed its own recipe for borosilicate glass in 1908, and Corning employee Jessie Littleton discovered a new use for the material after his wife Bessie used a sawed-off borosilicate glass battery jar for baking. Seven years later, Pyrex cookware hit the American market. The company referred to its products as “fire-glass” in early ads.

These dates are important because Corning’s patent on the borosilicate glass used to make Pyrex pans expired in 1936. At that time, the company developed a new formula for aluminosilicate glass, which it used to create a line of frying pans called Pyrex Flameware. (This line was discontinued in 1979.) The real roots of the current controversy were planted in the 1950s, when Pyrex began making cookware out of tempered soda-lime glass. Corning licensed the Pyrex brand to a company called World Kitchen—now known as Corelle Brands—in 1998, and by nearly all accounts, all Pyrex cookware sold in the United States after that year has been made of tempered soda-lime glass. This is where the controversy really heats up.
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How much better older (or European) borosilicate Pyrex is than newer soda-lime glass Pyrex is up for debate. Exploding Pyrex incidents have happened, since the World Kitchen takeover, however. An oft-cited Consumer Affairs investigation from 2008 showed some pretty gnarly accounts of people doing simple things like putting a hot Pyrex pan in the oven only to have it explode in their hands, sending scalding shards of glass into their appendages. There are photos of the injuries, too, so be careful clicking through to the report. At the time, World Kitchen denied any responsibility in the incidents, stating that “reports of explosions comprise an extremely small percentage of the 370 million Pyrex dishes on the market, and are often the result of the consumer failing to read the instructions or of a consumer mistaking a competitor’s product for a Pyrex dish.” The company later disputed other aspects of the Consumer Affairs report.