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.
All modern pyrex is tempered soda lime glass, which has good physical shock resistance but less than great thermal properties. Old school pyrex is borosilicate glass, which has outstanding thermal properties but is a bit less shatter resistant and is also more expensive to produce then tempered soda lime.
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.
They switched formulas after Corning spun off its consumer products division in the late 1980s to Corelle Brands. The change was sold and justified by the company as making the glass safer, but it was seen by consumers as a cost cutting decision by management to make the new company more profitable.
Additionally, Corning's introduction of soda-lime-glass-based Pyrex in the 1940s predates the introduction of the all lowercase logo by nearly 30 years.
The best way is to look at the bottom of the product. My vintage Pyrex, which is at least 40 years old, and definitely boro-silicate, reads “Not For Lab Or Stovetop Use - Corning N.Y. - U.S.A. - 516 - PYREX.” Newer products made of soda-lime glass do not read Corning N.Y., nor are they made by Corning.
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.
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.
Patterned Pyrex—such as the 1956 Pink Daisy or the 1983 Colonial Mist colorways—tend to be valuable as a collector's item. Other popular patterns include the 1957 Butterprint, which features an Amish couple and their crops, and has been valued at a few hundred dollars.
Corelle Brands is home to iconic, category-leading brands, including Instant™, Corelle®, Pyrex®, Corningware®, Snapware® and Chicago Cutlery®. We're passionate about delivering products that facilitate the joy we find in cooking and sharing food with family and friends.
For the home, the first set of colored Pyrex opalware was introduced in 1945 in the form of the primary color mixing bowl set.
According to the agency, demand for the popular glass measuring cups became so great in 2020 during the pandemic that Instant Brands shifted production to China while continuing to market them as being manufactured in the U.S.
This can be tested by heating a small piece of glass and observing how much it expands. Weight: Borosilicate glass is generally denser and heavier than soda-lime glass. Clarity: Borosilicate glass is known for its clarity, while soda-lime glass can have a slight green tint.
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.
The next time you go to cook dinner in a Pyrex pan, take a look at the labeling. 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.
It's tempered, meaning it's been heated and cooled in a manner that makes it more durable under future temperature fluctuations. It's less likely to break under an impact, and when it does, tempered glass breaks into diamond-like cubes instead of long, pointy shards, so it's a little safer to deal with.
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. (In Europe, Pyrex is still made of borosilicate. So these recommendations only apply to Pyrex in the United States.)
The name Cinderella was applied to quite a few different Pyrex products from carafes to butter dishes but the spout and handle nesting bowls marked the first use of this name.
The 1980s saw the last designs of Decorated Bakeware, Pyrex's beloved opalware line. The last four patterns produced were Autumn Harvest (debuting in 1979), Shenandoah and Forest Fancies (debuting in 1981) and Colonial Mist (debuting in 1983). Production of Decorated Bakeware ceased in 1986.
Everyone loves a good kitchen hack, and one of the most popular examples concerns glass cookware. Between Twitter, Reddit, and TikTok, there are hundreds of posts asserting that all-caps PYREX is the good stuff (aka, borosilicate glass), and all-lowercase pyrex is junk (aka, tempered soda-lime glass).
So, why did Pyrex make the change all those years ago? Two primary causes: increased air pollution regulations and a focus on reducing energy consumption. Soda lime glass is better for the environment, requires less energy to produce, and is more easily recyclable—making it the preferable choice.
Decorative patterns are also key to determining the glassware's value. Lucky in Love, a sweet pink and green design, is prized for its rarity and promotional production. Wright notes that Amish Butterprint, Pink Gooseberry, Snowflake Blue, Crazy Daisy and Friendship are also considered valuable in the Pyrex community.
The bowls in the Pyrex Atomic Eyes Chip and Dip, sans bracket. Image courtesy of JennifersVintageFind. A highly-coveted pattern, the Atomic Eyes Chip and Dip is the holy grail for some Pyrex collectors. Released in the 1950s, some of the bowls feature a Pyrex stamp while others don't.
Rare patterns and colors have sold for up to $10,000! More common pieces don't come close to those numbers but are still coveted for their extreme durability. Although every dish made before 1999 is considered vintage, older pieces (from the 1970s and earlier) are the most valuable.
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.