Some people also try to seek out older Pyrex pieces made of borosilicate before the company made the switch to tempered glass, but exactly when the change happened is hard to pinpoint. To me, what we have to worry about are the flaws in the glass surface.” As long as you follow the manufacturer’s instructions and avoid using tempered wares on the stovetop, under the broiler, in a toaster oven, or on a barbecue grill, stress relaxation is very unlikely to occur. Other uses for Pyrex that were once common, like using them on the stovetop, are no longer recommended since the formulation for borosilicate Pyrex glassware is different than when the company first started creating Pyrex Flameware for stovetop use. This phenomenon usually occurs when something cold is heated up too quickly. “CPSC has investigated incidents with glass cookware,” Davis told us. As it turned out, the company cautioned against putting cold (or even room-temperature) Pyrex pie plates and baking dishes onto hot baking sheets because they conduct heat so efficiently that they could shatter. Potholders or towels that are completely dry should be used while the Pyrex is cooling off so as to keep it from resting on a cold stone countertop or stovetop. How much will a midwifery schooling cost? As long as your baking dish is the right shape, it should be OK for baking, right? When you buy through links on our site, we may earn an affiliate commission. This shock causes different parts of the glass to expand at different rates and often crack from stress, making soda-lime glass a poor candidate for bakeware. TAP ON IMAGE TO VIEW PRICE. This is partly because the brand is so popular in the US, but also partly because its bakeware used to be less prone to breaking from thermal shock. Our new recommendation is to place the pie plate on an unheated metal baking … Other than being completely surprised (and a little annoyed about having to clean tiny bits of glass out of my sink), I was unhurt, not even a scratch.”. The publication references the tests performed by Consumer Reports, which used dry sand heated in casserole dishes. Photo: Michael Murtaugh. This avoids blasting your Pyrex with the super-high temperatures that some ovens create in the first minutes of heating up to achieve the required baking temperature quickly. “The atoms in there are stressed and they’re trying to pull themselves apart,” explained Jane Cook, PhD, the former chief scientist at the Corning Museum of Glass. It’s true that tempered glass is more susceptible to thermal shock than borosilicate, but experts disagree on how much more susceptible it is—and we think some calculations may exaggerate the risk under normal use. “As I see it, the real problem with tempered glass bakeware is its complex shape, which is very difficult to uniformly temper,” LaCourse told us. According to Pyrex’s safety and usage instructions, “While the glass is designed for temperatures typically used in baking, it can break when exposed to the direct heat element while the … These pieces are durable, but certainly not invincible. You can choose borosilicate bakeware like the OXO Good Grips Pie Plate (the main pick in our pie plate guide) and the OXO Good Grips Baking Dish (the budget pick in our casserole dish guide). All that said, it’s also important to remember that flaws such as surface scratches, chips, or small cracks may lower the ability of any type of glass to withstand dramatic temperature changes. “There is no single number for the actual Delta T [or the temperature differential] that a particular glass can withstand because it depends on how it’s been handled and what the cracks or surface flaws are in the material.” The various formulas, thicknesses, and shapes of the bakeware also affect the differential.