Our Favorite Finds: Vintage Pyrex

The origins of Pyrex lay in a problem the early-20th century railroad industry found themselves facing with broken lantern globes. When they were hot, contact by rain or snow would cause them to crack. They engaged Corning Glass to come up with a solution, which they did in the form of a borosilicate (Type of glass with silica and boron trioxide as the main glass-forming constituents) non-expansion glass formula they dubbed Nonex. Although it was the perfect answer to the railroads' lantern breakage issue, it was overall unprofitable since few of the new type globes required replacement afterwards.

Nonex found success in other areas, however, including wet cell battery jars("Wet cells" were open containers that held liquid electrolyte and metallic electrodes. When the electrodes were completely consumed, the wet cell was renewed by replacing the electrodes and electrolyte. Open containers are unsuitable for mobile or portable use.). When her ceramic casserole cracked, it was one of those battery jars, cut down to make a baking dish, that Corning researcher Jesse Littleton brought home for his wife to try. Within her experiments with it, she found that the foods cooked faster, at lower temperatures, with the added benefit that she could see the food as it cooked.

With the Nonex formula altered to remove lead, they proceeded to develop a cookware line from it, which the company called Pyrex. And, as cookware, although expensive for it's time, Pyrex proved quite the success, selling over 4 million pieces its first four years of production and an additional 26 million over the following 8 years.

The Great Depression in 1929 dealt Corning and Pyrex a great challenge. Part of its high cost lay in the fact that, even though annual production numbered in the millions, the pieces were still individually blown by hand. Corning was able to survive the poor economy by switching its Pyrex manufacturing process to automated machine pressing, thus enabling a reduction of retail prices by 30-50%.

While Pyrex wasn't the first high heat suitable glass of its kind, it definitely became the most successful in terms of both the scientific ware and kitchenware produced from it.

As kitchenware, and as bakeware in particular, Pyrex was marketed as being the most versatile. Advertisements broadcasted, just as Mrs. Littleton had ascertained, that it heated evenly, absorbing and conducting heat instead of reflecting it like most metal utensils would. Its transparency allowed the cook to observe the doneness without uncovering. Bread was advertised as rising better, and pie crusts as crisping on both bottom and top.

When the request came for a more durable messware for the military (Messware, designed specifically for military use, was a precursor to Pyrex and Pyrex Opal Ware) , Corning turned its attention to the opal ware produced by MacBeth-Evans, the Charleroi, PA glass company with which it had merged in 1936. The dinnerware developed was later marketed to the hotel and restaurant industry, and would eventually become the basis for the opal glass oven and kitchen ware popular over the next half century.

During World War II, ads stressed that Pyrex ware saved valuable food by allowing cooking, serving, refrigerator storage, and reheating and serving leftovers all from the same utensil without waste. Post-war, new brides were bombarded with Pyrex advertisements in every national magazine.

The introduction of color ware in the fall of 1945 and, later, new styles and decorative patterns would further reinforce the attractiveness of the dishware. The 1950s and 1960s saw the release of dozens of seasonal gift items, and the advertising focus shifted to their promotion.

New standard patterns and promotionals continued to be introduced up until about 1983. In 1986, however, US Pyrex opalware was all but discontinued. Curiously, Pyrex casseroles produced in England were imported and marketed for a brief time.

In the post-opal ware era, Corning continued to cultivate consumer interest for color and decoration by offering clear ware bowls painted in a variety of shades. Subsequently, sculptured and also tinted clear ware were produced.

Since so many Pyrex pieces were made for a short time, part of the fun is finding unexpected items—canning jars, baby bottles, and even percolators with wooden handles. Although antiques dealers are beginning to carry it, Pyrex usually turns up in more modest settings, such as yard sales, flea markets, and thrift shops.

The price often depends on the object's desirability and condition. While a set of old custard cups may fail to sell for 50 cents, a four-color, four-piece mixing bowl set can cost from $45 to $65.

Patterned Pyrex—such as the 1956 Pink Daisy or the 1983 Colonial Mist—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. You will want to identify which pattern you have and its year to determine how much it's worth in the marketplace. "Depending on condition, expect anywhere from $100 per piece to $500 for a collection or a unique Hot 'N' Cold chip and dip set," says Martin.

Condition can determine whether an object is desirable or merely junk. Even without its stem and basket, a percolator in good shape makes an attractive coffeepot and can sell for $15 to $20, or for about $50 for a complete model. But colored Pyrex must look shiny and new. "A lot of it was ruined by dishwashers," says David Ross, a vintage-kitchenware dealer from Melrose, Massachusetts.

Practicality can also affect an item's allure. Cinderella nesting bowls—a late 1950s design flanked by a pair of lips for gripping and pouring—are less popular with collectors than the lipless bowls. This is mainly because the lipped bowls take up a lot of room in kitchens.

Pyrex is easy to authenticate because pieces were marked with a logo. In their book, Rogove and Steinhauer show 23 back stamps used between 1915 and 1965 to identify Pyrex. Some of the stamps can also be used to authenticate Flameware—the aluminosilicate glass Corning manufactured between 1936 and 1979 for percolators, double boilers, and other items used on the stove top.

Authenticating other items can be more of a challenge, but there are a few obvious indicators to look for. Clear glass manufactured until 1934 has a yellowish tinge due to the arsenic added to help shape the glass. Flameware made from 1936 until shortly after the war was tinted blue to distinguish it from Pyrex. And mixing bowls from the '60s are thinner than those made in the '40s.

In many ways, Pyrex is as practical today as it was 40 years ago. The retro glass pieces can go in the oven, the freezer, and the refrigerator. With that being said, some colored Pyrex has metallics in the paint, it probably shouldn't go in the microwave. Pyrex should also be washed by hand, as dishwasher detergent can destroy the color.

Pyrex prices can be tricky to discern for a variety of reasons, most having to do with regional differences. A piece worth $50 in one location may be worth only $25 in another for reasons that may be impossible to determine. It could be that for whatever reason the $50 location simply has less of that pattern in its market. Who knows?