And does it mess up the pan?
Woman Places Asparagus in Oven
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Place a sheet pan in your oven and you might soon hear a reverberating "PONG!" that makes you jump a mile out of your shoes. Before you open the oven door to check for casualties, it helps to know a little of the physics behind that sound: This is the metal warping, or twisting slightly as it expands and contracts.

So why does that pop take place? And is it something you need to worry about? We get to the bottom of both and share tips for keeping sheet pans from warping the next time you roast, toast, or bake.

Why Do Sheet Pans Warp?

The metal of your sheet pan is at a cooler temperature than your hot oven. Metal expands as it heats. The large surface of your sheet pan will heat and expand faster than the short rimmed sides. This creates stress right where the flat base meets the raised lip, causing some pans to buckle or twist.

Thin metal sheet pans tend to warp more often than heavier ones, but all pans are likely to warp at least a little at some point.

Is It Bad for Sheet Pans to Warp in the Oven?

The short answer is not really.

Sheet pans will usually straighten out as they come up to temperature. A slightly warped pan will also perform just as well as a regular one.

The pop you hear isn't quite strong enough to fling food onto the walls of your oven, so no worries there either. The main instance where it might make a difference is when it helps to have a very flat surface, like if you're pouring an egg mixture into a crust for a quiche or making créme brûlée.

How Do I Keep My Sheet Pans From Warping?

First, try to avoid placing cold pans in a hot oven. If you need to chill balls of cookie dough, do this on a plate instead of sticking your sheet pan in the fridge before baking.

You can also place an empty sheet pan in the oven as it preheats — a great trick for getting roasted veggies extra crisp. For cookies though, it's better to preheat the pan for just a couple of minutes or to run hot water over it first, as a pan that's too hot could cause cookies to spread too fast.

Second, use the right-sized sheet pan for the job. The surface of the sheet pan should be topped evenly with whatever you're roasting. Any bare spots will heat faster than ones covered by food, and that temperature difference could cause your pan to warp. Be careful not to crowd your pan as veggies need some room to brown, but do try to fill in bigger gaps.

Third, be aware of your oven's hot and cool spots so you can place your sheet pan where the heat is most even. Generally, the oven is hottest at the top and bottom center, where the heating elements are, and on either side (the walls of your oven). Try placing pans in the center of the middle rack, rotating the pan from side to side or from front to back during cooking if needed.

Ready to stock your kitchen with the best sheet pans? Check out our best tested and reviewed baking sheets.