The secret is simple—check the logo. If the brand name is in all capital letters, it's vintage Pyrex. If it's all lowercase, it's modern.
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.
New Pyrex is better at handling physical bumps and bangs (drops, banging into the counter, etc). Old Pyrex is better at handling temperature shock (setting onto wet counter, taking out of freezer and putting directly into preheated oven, etc).
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.
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.
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.
Baking glassware such as Pyrex dishes in usable condition should be donated to local thrift stores or otherwise reused. If unusable they should be thrown away in the trash. They should not be added to curbside recycling. They are made of a different material than glass bottles and jars.
Corning has licensed out the use of their PYREX® (upper case lettering) and pyrex® (lower case lettering) logos to 2 different companies. They are not the same products!
Some of the most elusive Pyrex pieces go for hundreds of dollars, and there are even anecdotes of collectors bidding thousands for rare pieces. A rare Lucky in Love Pyrex casserole dish from 1959—what might have been only a test pattern, made of shamrocks and hearts—sold for $5,994 in a 2017 Goodwill auction.
The brand, Pyrex, has historically owned the trademark for little-p pyrex, but its parent company, Corning, has since sold it. Lowercase "pyrex" is produced by other cookware companies that don't use the heat-resistant borosilicate glass the original company does (more on that below).
The USDA Food Safety and Inspection Service has deemed Pyrex as microwave safe. There are some things you need to know though! Pyrex is made of either borosilicate or soda lime glass and is heat resistant up to 425 degrees Fahrenheit, making it a good option for microwaving.
If the logo is in upper case lettering, PYREX, it's most likely made of borosilicate, and thus safer. The lowercase lettering is most likely made of soda-lime glass, so take extra care after any high-heat cooking.
Each Pyrex piece is assigned a model number, though some of the earliest sets of color ware pieces do not have them. Model numbers are typically found on the bottom of your glassware, though sometimes they are located elsewhere—look for them above the trademark on your dishes, and around handles and edges of lids.
Pyrex dishes also hide a little secret code: Many contain a three- or four-digit number that corresponds to a specific dish. A series of Mixing Bowls will feature 401 (1.5 pint), 402 (1.5 quart), 403 (2.5 quart), 404 (4 quart). The iconic two-quart green-and-white casserole dish is a 232.
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.
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.
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.
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.
Can Pyrex be recycled? While Pyrex ovenware is a type of glass, it has been specially treated in the manufacturing process to withstand high temperatures, which makes it non-recyclable. Broken or chipped Pyrex should be disposed of carefully in the waste bin.
While vintage Pyrex is durable and even safer than newer tempered glass dishes, it's still essential to follow some precautions to ensure safe use. First, always bring your vintage Pyrex to room temperature before placing it in the oven.
The gummy yellow and brown residue is an accumulation of grease and oils, so although nonstick spray can be our friend in the kitchen, it can be the enemy of glass bakeware.
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).
On a molecular level: heated material expands, while cooled material contracts. Brittle materials like glass are much more vulnerable to thermal shock, because they break when their molecules quickly expand under heat or contract under cold.
Corning divested itself of the Corning Consumer Products Company (now known as Corelle Brands) in 1998 and production of consumer Pyrex products went with it. Its previous licensing of the name to Newell Cookware Europe remained in effect.