Why Pyrex Needs To Be At Room Temperature Before Going In The Oven
Created in the early 1900s, Pyrex is a brand of glass bakeware that is ubiquitous in home kitchens. Great for making pies, loaf breads, or hot and savory dishes like yellow squash casserole, Pyrex produces easy-to-clean, affordable cookware that is versatile and can last a long time.
Pyrex dishes are pretty low-maintenance, but there is one thing that it pays to remember: even though Pyrex can withstand both high and low temperatures, the material cannot handle extreme temperature changes. Going immediately from cold to hot or vice versa can cause your dish to crack or even shatter, so if you are planning to bake or reheat food in a Pyrex dish, it is very important that you allow the dish to come to room temperature before you put it in the oven. The same goes for putting it in the fridge, allow the dish to cool before covering and chilling. If you fail to follow this guideline, you could lose your Pyrex, and your meal along with it.
Why Pyrex can't handle extreme temperature changes
The reason that you have to be careful about Pyrex and extreme temperature changes has to do with the way Pyrex responds to heat. When exposed to heat, Pyrex expands. When it is exposed to the cold, it contracts. But glass cannot handle being asked to expand or contract too rapidly, and this can cause it to crack or shatter. This is called "thermal shock," and it can ruin your cookware. It is a particular risk with newer Pyrex dishes, since Pyrex changed the type of glass it uses in 1998 to one that is less resistant to temperature shock.
If you are working on a recipe that seems to require a big temperature change (sometimes pie crusts need to be chilled before baking) you might be worried about an issue with your Pyrex. Here's an easy workaround: Freeze your pie crust in the Pyrex, and then when the crust is properly frozen you should be able to remove it from the dish. You can wrap the crust and put it back in the freezer while the Pyrex comes to room temperature. Once it's time to bake, simply reunite the crust and the Pyrex and put them in the oven. You can have a perfect pie crust without the risk of thermal shock.