Of all the general truths of the kitchen I’ve come to know over the years, I feel like the one most deeply-ingrained within me is that hell hath no fury like a woman whose Pyrex was unreturned. Pyrex was always synonymous with the heavy-duty, “fancy” cooking stuff, but I never knew why the seemingly unassuming clear casserole dishes and red, blue, and yellow nesting bowls were so coveted by so many -- not just the women in my own family.
It all started at a railroad. In 1908, Corning Glass Works started making Nonex, a thermally resistant, non-expanding glass for railroad signal lanterns. This borosilicate glass, originally invented by German scientist Otto Schott, could withstand the drastic temperature changes of the hot lamps and cold rain and snow without cracking. This proved to be useful to Corning employee Jesse Littleton’s wife as well; after her cake mold broke, Littleton brought home a sawed-off borosilicate glass jar to use instead. The repurposed battery jar made for an excellent bake, prompting the invention and soon-to-be international wave of Pyrex.
Pyrex is derived from the company’s tradition of using “ex” at the end of their product names and the Latin prefix “pyro.” Originally advertised as “fire-glass,” Pyrex could withstand drastic temperature changes, didn’t discolor or retain food smells, and didn’t react with ingredients to change the overall flavor like cast iron. Additionally, the clear glass allowed bakers to watch the sides of their cakes, pies, and casserole brown in the oven. The new kitchenware was an instant hit, selling four million pieces in its first four years of production and twenty-six million pieces over the following eight years.
Even though the sturdy glass dishes seem commonplace these days, Pyrex advertised almost exclusively to the wealthy in its early years. Pyrex’s trademark ability to withstand drastic temperature changes was less important to lower-income families who didn’t own a refrigerator in the first place. The kitchenware’s original advertisements also featured only maids using the products, a clear indicator of their wealthier target audience. This was due in part to high production costs: each Pyrex piece was manufactured by hand.
When the Great Depression hit, Pyrex plants switched to automated production to soften the blow of the recession. This new production process made it much cheaper to make, which in turn made it cheaper to buy. By 1936, the business was booming, and just in time, too. Three years later would usher in the start of World War I, and Pyrex was quick to capitalize on the patriotic duty train. Advertisements started touting that buying Pyrex was patriotic -- the glassware helped save precious metals for the boys overseas, and the ability to cook, serve, store, and reheat food in one utensil saved on food, water, and time.
Out of this booming business, Corning Glass Works purchased a glass factory in Charleroi, Pennsylvania just outside of Pittsburgh. This factory could make opaque glass with the same heat-resistant properties as the original clear Pyrex. Originally used in military mess halls, the colored thermal glass entered the common kitchen with the iconic primary-colored nesting bowls of 1945. The colored, opaque glass from Charleroi offered endless opportunities for new designs and set themes, creating a massive catalog of floral, bohemian, mod, and classic prints. After the opalware was discontinued in the late 1980s, the decorative Pyrex pieces quickly became some of the most valuable.
From there, Pyrex both clear and colored continued to accumulate in kitchen cupboards across the globe. The kitchenware’s long lifespan allows pieces to be passed down through multiple generations and dispersed to flea markets and thrift shops around the world.
Not all Pyrex is created equal. Pyrex printed both standard and promotional patterns onto their kitchenware. Standard patterns would be manufactured for at least two years, while promotional patterns were featured on a limited number of pieces and only sold for a limited amount of time. Obviously, promotional patterns are much harder to come across -- and when they do pop up at the random estate sale, they can go for quite a pretty penny. “Lucky in Love,” the most in-demand limited-edition pattern, recently sold for $6,000 at a Goodwill auction.
But not to worry -- stocking your shelves with authentic vintage Pyrex doesn’t always require taking out a second mortgage on your house. There are plenty of classic patterns circulating around, some of which include:
While it's been released in several color iterations, the most common is pink on white or white on pink. The Gooseberry print was discontinued in 1966, but you can still find it on sites like Etsy.
The Pyrex snowflake print was the first printed pattern on the opal Pyrex line released in 1956.
Pink Daisy was introduced as part of the "NEW Pyrex Decorator Casseroles" line and featured a clear dish that could be used as a trivet or an extra serving dish. See more for sale on Etsy.
Released in 1957, Butterprint was released in response to a growing trend of colonial American decorative themes. You can pick up some of your own here.
A pattern near and dear to my heart, Butterfly Gold is a classic 1970s print that was released as a Compatibles pattern for the Correlle Dinner Ware pattern of the same name. You can find some originals for sale on Etsy.
Another personal favorite of mine, the Early American print was advertised as the "theme of the decade." Fun fact: it was also released in Canada, but appropriately renamed "Early Canadian." Find them for sale here.
If you’ve been bitten by the Pyrex bug and are interested in sinking some serious cash into your collection, it’s important to know how to identify proper Pyrex from the knock-offs. While plenty of clear glassware is currently in production today, scammers will often try to capitalize on the shrinking supply of discontinued decorative Pyrex. To ensure you’re adding an authentic piece to your collection, look for the glass markings -- specifically, the small logos molded into the bottom of each Pyrex piece, called backstamps.
The oldest Pyrex backstamps feature “Pyrex” in all capital letters inside of a circle. The circle also contains a “CG” for Corning Glassworks. Another classic backstamp can be found on pieces made by the glass factory in Charleroi prior to the adoption of the Pyrex name. The original owners of the Charleroi plant, the MacBeth-Evans Glass Company, used a special trademark symbol on the bottom of their pieces not used on previous products or products made after the Pyrex name was introduced. That symbol is of a glassblower, or “gaffer,” nicknamed Little Joe.
Another way to authenticate your vintage Pyrex is to look for inventory numbers on the bottom stamps of casserole dishes and bowls. If the backstamp includes any information on where or how to use them, chances are that the piece was made post-1970. Of course, verifying features can be worn off with normal use and cleaning over the years, so if you want to be 100% sure, contact a local antique appraiser or other vintage experts.
To start curating your very own Pyrex collection, start close! Ask your family members or close friends if they know of any old Pyrex that may be collecting dust somewhere -- you’d be surprised how many casserole dishes were gifted in the 70s and then forgotten as quickly as everyone’s Pet Rock. Collecting hand-me-downs from loved ones adds as a special touch of sentimentality to your kitchenware collection, and that is priceless in and of itself.
Next, look locally. The best ways to find Pyrex in your own backyard are by visiting yard and garage sales, church rummage sales, and estate or moving sales. It’s also worth checking out your local Goodwill, Salvation Army, pawnshop, or flea market. Antique stores might have a few harder-to-find promotional items tucked away, but be cautious of price gouging. Higher-end stores will often overprice commonplace Pyrex pieces under the guise of rarity in an effort to dupe unassuming Pyrex-seekers.
Then, of course, there is the internet -- the place you can find everything and anything, even the things you didn’t know you wanted, including authentic vintage Pyrex. eBay and Craigslist are two great places to start, although these sites do present greater inherent risks you should be aware of before making any major purchases. Other seller-to-consumer websites that boast a wide range of Pyrex pieces include RubyLane.com, PyrexLove.com, and Etsy.com.