Why Your Glassware Spontaneously Breaks (Hint: It’s Not You)

Pop. Boom. Crash. The hallmark, stop you in your tracks, sound of the worst thing happening: Your glass kitchenware breaking with seemingly no good reason. Besides the messy cleanup, and the potential of a lost meal you worked so hard for, it’s more troubling than anything. Why can’t I trust my “unbreakable” bakeware not to spontaneously combust on me? Is nothing sacred?

People report millions—trillions, even—of tiny glass shards catapulting across their kitchens in scenes that would rival a blockbuster movie stunt. (Coming this Christmas Day to a kitchen near you…) Entire Reddit threads are dedicated to talking about glassware mishaps, and thousands of TikToks show absolute kitchen carnage. Baking and cooking projects increase by 73 percent during the months of October through January. Your all-purpose cookware gets more use, and, because of the holiday rush to complete everything on your guests’ food wishlists, mishaps are way more likely. But, it’s not your fault. Read on for how to safely cook and bake with your glass kitchenware this season.

So, why did your glass dish shatter?

Glass, though very durable, isn’t completely indestructible. Well+Good’s very own Deputy Editor, Chloe Metzger, had an incident involving a late-night scare. “I saw some shards of glass on my kitchen counter,” she recounted in a Slack message, “and I discovered that my massive glass mixing bowl had spontaneously shattered into a trillion pieces with a force that blew the cupboard door open.”

It even happens to the pros. Clare Langan, culinary consultant and private chef, once had a baking dish “filled with lasagna shatter into a million pieces.” 

Whether on the counter, or in the oven, there are plenty of ways your glass bakeware can suddenly become an abstract work of art in your kitchen. Thanks to thermodynamics, quick temperature changes can make the glass unstable and therefore, breakable. Some examples of this include:

1. Taking a glass baking dish out of the oven and placing it directly on a cool countertop. The uneven change in temperature on a concentrated part of the glass—the bottom—creates opportunity for the glass to break apart.
2. Stacking glass bowls after washing in hot water. A water-warmed bowl or dish touching colder glass disrupts the other tempered glass items, which in some instances, can cause breakage. 
3. Transferring directly from fridge to oven. Much like the oven-to-cold-counter pipeline, having more heat on the bottom of the glass dish, resulting in an uneven heat, and potential for disaster.
4. Putting hot food into a cold container. Hot to cold or cold to hot is going to open up opportunities for the molecules of the glass to become insecure. 
5. After transferring food to another container, placing a still-hot glass dish in the sink. Your sink is probably some sort of stainless steel and is likely very cold. The same thermodynamic rules of cold countertop apply here, too. 

PYREX vs pyrex

Though the laws of heating and cooling quickly can explain some of these instances, there’s another factor at play: Glass types. And, you’re not imagining it: Instances of glassware breaking have increased in the last decade or so. It all comes down to a few capital letters. 

Founded in 1915, Corning Glass Works created the Pyrex line of glass wares. Used in both homes and scientific labs, Pyrex became the go-to for everything from beakers to pie plates to sturdy glass casserole dishes. This era of glassware was made with borosilicate glass—created from the compounds of silica and boron trioxide—known for its ability to be majorly heat resistant. So heat resistant, that it can withstand a 333 degree temperature change without flinching. (Read: Violently breaking.) These products are denoted as capital P, PYREX.

In 1998, Corning moved the kitchenware side of production to another company, Corelle, who still produces glass products for the home today with the same Pyrex name, but in all lowercase (pyrex). One of the major problems they set out to tackle was, funnily enough, breakage. Accidents happen, and consumers were reporting that when they did mistakenly drop their glassware, it broke into large, jagged pieces that could cause injury. To solve for this, they switched from borosilicate to soda-lime glass, a glass that makes up about 90 percent of all glass items in our lives. 

The benefit was how soda-lime breaks: Instead of gnarly, rough chunks, it evenly breaks into little tiny pieces that are less harmful overall. You see where this is going, right? Soda-lime breaks “nicely,” but it is also far less heat resistant. A 234 degree difference, in fact. Soda-lime glass can only withstand a 99 degree quick temperature change. For reference, when you open your oven, it drops about 30 degrees almost immediately. That’s almost a third of what soda-lime can stand to lose. Nowadays, when your glass dish breaks, it *really* breaks, thanks to soda-lime glass.

Ways to prevent breakage

Glass baking dishes are still a great option for cookware. They’re easy to clean, display your hard-earned cooking feats, and with care, will last a lifetime. 

1. When vintage shopping, look for the capitalized PYREX. That way you know it’s made with borosilicate glass, which will be sturdier.  
2. Use a soft trivet (think: silicone or cloth) under a very hot or cold glass dish. Avoid a metal trivet, as their temperature difference, combined with their concentrated pressure points on the glass, could lead to breakage.
3. If your empty glass dish is still hot after transferring food, wait until the dish has cooled before putting it into the sink to wash.
4. Try to avoid instances of extreme temperature changes. Transfer your leftovers to a microwave-safe bowl before reheating, avoid cold surfaces after pulling a dish from the oven, and try not to stack dishware that’s hot from a wash in the dishwasher or sink.
5. If you’ve sworn off glass dishes after reading this, try ceramic bakeware. Ceramics have a lot of the same benefits as glass, but are less prone to shattering.