Any Southern cook worth her salt knows and trusts several brand names when it comes to cook- and bakeware that gets the job done better than anything else. Along with Le Creuset and Calphalon, Pyrex is one of those relied-upon brands for everything glass, from measuring cups to casserole dishes. The brand has been around for over 100 years, and has established a reputation based on its material that was strong enough to be used in kitchens and laboratories alike. What you may not know is that Pyrex is no longer made of the same type of glass it once was—but, before we set you into a panic, understand that this change didn’t take effect recently.
Pyrex products were made of borosilicate glass until about 60 years ago, at which point they began switching 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.
This change is worth mentioning because borosilicate glass was made to withstand large and sudden temperature swings (or thermal shock) better than many other glass varieties. It meant that the odds were in your favor when it came to your casserole dish making it safely from the icebox to the oven and back again. Unlike other glass and ceramic cookware, Pyrex dishes could withstand extreme temperature changes, which made them a kitchen standby.
So, why did Pyrex make the change all those years ago? Increased air pollution regulations and a focus on reducing energy consumption were two of the primary causes behind the move. Soda lime glass is better for the environment, requires less energy to produce, and is more easily recyclable—making it the preferable choice. Environmental issues aside, tempered soda lime also stands up to sudden impact better than borosilicate glass, which Pyrex says is the most common type of damage consumers are faced with. In an email from a Pyrex representative it was noted that less than one-tenth of one percent of millions of Pyrex goods sold each year result in thermal breakage.
Though it may not be the same Pyrex glass the brand launched with in 1915, chances are, the Pyrex sitting in your cabinet is in fact just like Mama’s (and Grandma’s, too). As long as you use it safely and appropriately, it will stand the test of time—and serve up plenty of good casseroles for years to come.