Pyrex products were made of borosilicate glass until the 1950s. At that point, they switched to manufacturing products with tempered soda lime instead. Today, every piece of bakeware made in the U.S. uses tempered soda lime, including the full line of Pyrex consumer glassware.
The brand switched its glassware formula in the 1950s, but has recently reintroduced borosilicate glass into some of its products, such as the Pyrex MealBox™ and Pyrex Hydration line.
I contacted Pyrex to ask if there's an easy way to tell what material your Pyrex dish is made from, and the company had a simple answer: Look at the logo. If it's all caps “PYREX,” it's vintage, made of borosilicate. If it's lower case “pyrex,” it's new, and it's soda lime.
Here's where the branding comes in. All-caps PYREX, which is sold and made in France, is still made of borosilicate glass. But any Pyrex that's all lowercase — a recent change in branding — is soda-lime glass, which isn't designed to withstand drastic temperature changes.
According to the FTC, during the pandemic, Pyrex measuring cups sold on Amazon.com were advertised as made in the United States. In reality, some glass measuring cups were imported from China.
The Pyrex formula changed in 2020. This change was made to make Pyrex glass stronger and better able to withstand temperature changes. The newly formulated Pyrex combines classic trusted heat resistance with improved thermal shock resistance, making it a better choice for glass cookware.
In fact, borosilicate glass is perfectly safe to use in both kitchen and laboratory applications. “Creating borosilicate glass requires much higher temperatures than those necessary for the production of regular glass. This makes it more difficult to manufacture, and uses more energy, making it more expensive.
This difference means that Borosilicate glass does not expand as much on heating, so it is less likely to break when heated. Pyrex is one particular blend of Borosilicate glass, with a particularly high heating tolerance.
If you're unsure which material your glass kitchenware is made from, you can try eyeballing it to make a rough estimation. Take a close look at the edge of your baking dish, container, or bowl and try to find a bluish-green tinge. If it's there, you've got soda-lime glass. If not, you've got borosilicate glass.
Anchor Hocking has been manufacturing tempered soda-lime-silicate bakeware for nearly 40 years. Prior to that time, annealed borosilicate glass bakeware was the standard.
Corning used borosilicate to produce all Pyrex products. However, the company that purchased the cookware products switched to soda-lime glass, adopting the name pyrex (spelled with all lowercase letters).
It could be counterfeit glass! Soda lime and Borosilicate glass look very similar, but perform completely differently. Lately, there has been a rash of counterfeit glass introduced into the glass-gauge industry, some so-called companies even illegally using the corporate names of legitimate glass providers.
Both trademarks were historically used interchangeably in the marketing of kitchenware products made up of both borosilicate and soda-lime glass. However, now Corning has licensed out the use of their PYREX (upper case lettering) and pyrex (lower case lettering) logos to other companies.
It is stronger than regular glass but it can still break or crack if it is dropped or hit hard. It is important to handle borosilicate glass with proper care to minimize the risk of breakage.
If it's all caps Pyrex, it's vintage, made of borosilicate. If it's lowercase Pyrex, it's new. And it's soda lime. You still have to be careful.
What Makes Pyrex Special. "Pyrex continues to hold its value because most of us associate it with memories of family and holiday gatherings and memories from their childhood," Wright says. "The vintage designs and patterns of Pyrex evoke a nostalgia, which adds to its value for collectors.
Cookware with lowercase logos are usually made of soda-lime glass and should not be heated up in the oven or microwave to minimize risk of them breaking. Cookware with logos in all-caps are typically made of borosilicate glass and can be heated at high temperatures without harm.
Borosilicate glass is more expensive to produce than ordinary glass due to the inclusion of boron trioxide, which adds to its thermal and chemical resistance. This increased production cost is often passed on to consumers, making borosilicate glass products more expensive.
Borosilicate glass is sold under various trade names, including Borosil, Duran, Pyrex, Glassco, Supertek, Suprax, Simax, Bellco, Marinex (Brazil), BSA 60, BSC 51 (by NIPRO), Heatex, Endural, Schott, Refmex, Kimax, Gemstone Well, United Scientific, and MG (India).
Pyrex products were made of borosilicate glass until the 1950s. At that point, they switched to manufacturing products with tempered soda lime instead. Today, every piece of bakeware made in the U.S. uses tempered soda lime, including the full line of Pyrex consumer glassware.
Borosilicate Glass is typically more expensive than soda-lime glass, the most commonly used glass for production. The increased cost of borosilicate glass can be attributed to several factors. First, the raw materials used in its production, including boron, are more expensive than those used in soda-lime glass.
Since borosilicate glass resists chemicals and acid degradation, you don't need to worry about stuff seeping into your water. It's always safe to drink from.
Is Borosilicate Glass Safe? Borosilicate glass is completely safe and non toxic.