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Don’t put hot glass in the fridge or freezer unless you know it’s made of thermal shock resistant material, such as borosilicate glass.
Picture this: It’s Thanksgiving and you’re baking your signature pumpkin pie. Rather than buying store-bought pumpkin puree, you decide to roast a fresh-from-the-patch pumpkin and make your own from scratch. You’re done with the roasting, and now you need to let the pumpkin cool before you can puree it. Dinner is in just a few hours, so you ask yourself: is it okay to toss the hot baking dish in the fridge so it cools faster?
Great question! As you may already know, some types of glass are susceptible to “thermal shock,” which causes glass to shatter when exposed to temperature fluctuations. And broken glass is a big no-no when cooking. The last thing you’d want is for your pumpkin pie to come peppered with fresh shards!
But don’t worry quite yet. As long as you’re using the right kind of glass, it is probably okay to put a hot dish in the fridge.
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Glass and Thermal Expansion
Before you decide to invest in any glass refrigerator storage bins or bakeware, you need to understand a little bit about how this material performs in various environments so you know which type of glassware to use for what. Glass has very specific thermal expansion properties. If the temperature fluctuates, it will either expand or contract depending on the environment.
When tossed in the oven or exposed to the summer sun in your backseat, glass expands. When it’s placed in the fridge or freezer, it contracts. Expansion or contraction is typically OK when it occurs on its own, but when it happens at the same time or in quick succession, things can go awry fast.
When standard soda lime glass is exposed to two extreme temperatures — such as when you take it from oven to fridge quickly — it will experience thermal shock and crack or shatter. Typically, this causes different parts of the glass to expand and others to contract, quite literally pulling the material in two different directions. This is a recipe for disaster and the reason why the glass shatters.
Use Thermal Shock Resistant Borosilicate Glass
How your dish responds depends on the material from which it’s made. Borosilicate glass, a kind of glass made from boron trioxide and silica, is by and large considered the best and most stable kind of glass for cooking. This type of glass is much more resistant to thermal shock than other options, which is why it tends to be the choice glass material for top-rated fridge storage containers, cookware and more. It’s also commonly used in laboratory glassware, electronics and lighting.
Other types of glass, such as soda lime glass or tempered glass, are not designed to handle temperature fluctuations well, so they shouldn’t be used in these applications. This goes for standard drinking glasses and some jars. Never place hot drinking glasses or jars in the fridge, as they are likely to shatter! If you do a lot of meal prepping or food handling at different temperatures, consider buying some reusable food storage bags or borosilicate containers that aren’t so fussy about temperature changes.
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Rule of Thumb: Keep Hot Stuff Out of the Fridge
Even though your glassware may not shatter, it’s important to remember that the fridge or freezer isn’t the best place for large quantities of hot food. Putting a steaming pot of soup or a big tray of hot roasted veggies in the fridge is OK once in a while, but don’t do it perpetually, as it can cause your fridge to heat up and work inefficiently. If it’s chilly enough outside (and critters aren’t a concern), toss food outside to cool it off. A fan or open window will help, too.
We’ll occasionally have a need for storing hot items in a cold fridge. In those times, it’s important to make sure you’re using borosilicate glass goods with a lid for the job.