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Why Do Baking Sheets Bend in the Oven?

Why Do Baking Sheets Bend in the Oven?

Warped baking sheets are not only unsightly, but they also fail to perform as they should when it comes down to baking. Making cookies on a warped baking sheet will result in unevenly baked cookies that may not look that appealing.

Fortunately, it is possible to fix warped baking sheets and prevent it from happening in the future. Keep reading to learn how to do so.

Why do baking sheets warp in the oven?

This is primarily caused by the expansion of hot metal and uneven or fast contraction afterward. For example, when you put a rim-less sheet baking sheet in the oven, it expands, ultimately causing it to warp. So that loud clang you hear is most definitely your baking sheet warping in the oven.

Metal molecules have a solid atom structure. Intense heat could make the particles move faster and clump away from the heat source. In the baking sheet, the heat is collected on the baking sheet’s bottom, making the edges and the inner side the cooler side of the baking sheet.

When the metal atoms move to the bottom of the baking sheet, it causes the metal to lose its structural integrity. This mostly happens faster on thinner baking sheets. So if you hear the metal sheet popping and cracking in the oven, it is an initial sign of a baking sheet warping.

Baking involves precision and constant monitoring of your bakeware and your heat source. The baking sheet may be heat resistant, but it is not prone to bending and warping. The extreme heat may cause the baking sheet to lose its natural shape if left unobserved.

As the surfaces start to heat the baking sheet, the baking sheet’s bottom heats up faster than the other parts of the oven. The bottom baking sheet is located directly over a heated surface, making the metal molecules prone to expansion.

Check this too: Can I Use Cast Iron on a Glass Top Stove?

This pulls the composition of the baking sheet farther from its original shape. In return, the empty spaces cause enough stress on the folded edges. Purchasing a thicker baking sheet and checking your oven’s temperature are just a few of the precautions to prevent the baking sheet from warping.

How to stop baking sheets from warping

Baking sheets will typically warp when heated too quickly or come into contact with a cold surface while hot. To prevent this from happening to your baking sheet, gradually bring it up to heat and wait for it to cool down before handling it.

Baking sheets are warping out for several reasons: temperature, cookware size, and material. Some baking sheets bend because of sudden temperature changes. If you overheat the material, it can also warp your bakeware. It may bend if the baking sheet is too big or thin for the specific heat source. Aluminum baking sheets and single-ply baking sheets are more prone to warping.

Prevent Thermal shock

When a baking sheet has to endure thermal shock, it may expand and contract in the process, causing the warping of your baking sheets. Thermal shock happens when the baking sheets are placed in an environment with unbearably quick temperature changes.

Heating or cooling your baking sheet will rapidly change the overall construction of the metal baking sheet. This effect is also why heated glassware and ceramics crack and break when cold water is placed.

Control High temperatures

If you cook your food at extreme temperatures, it can also induce thermal shock. For example, preheating your oven before placing cold cuts will create an uneven temperature. But, heating your baking sheet too fast can also warp the bakeware.

High baking sheet temperature or preheating it will cause the sheet to expand unevenly, causing it to warp. Also, if you happen to use a low-quality baking sheet, it may not conduct and retain heat efficiently.

Use the right-sized baking sheet

There are also situations when your baking sheet is too big for the burner. This means that if the baking sheet can almost reach the oven’s sides, it can distribute heat abnormally.

This makes the sheet more accessible to the heat source faster. Getting the baking sheet’s right size will prevent the baking sheet from overheating.

Use a thicker baking sheet

Uneven heating is one of the significant reasons why baking sheets warp. Baking sheets with thin walls or thin metal layers are more susceptible to warping. The lighter metal is less efficient in conducting heat evenly.

Thinner baking sheets also have more noticeable heat and cold spots that could induce warping when heated at higher temperatures.

The baking sheet’s material matters

Baking sheets made with aluminum are more likely to warp than stainless steel. This is because materials like aluminum and copper are softer, with a looser molecular structure than some other solids.

This gives the baking sheet an avenue to expand and contract more easily. In addition, baking sheets made with cast iron and stainless steel have a tighter molecular structure, making them more resistant to higher temperatures.

Avoid Single-ply bakeware if you can

Several bakewares are constructed with multiple layers of metal. If your baking sheet is not coated or mixed with several elements, it is single-ply. Single-ply bakeware are only made with one material and costs cheaper than multi-ply baking sheets. Purchasing specialized bakeware may reduce the warping effect better.

How to fix a warped baking sheet

If you have a warped baking sheet, there are still ways to fix it. The methods are based on how worst the warping is. If it looks like twisted metal, there is no other way of flattening the metal. On the other hand, if the warping appears like tiny bumps or could not lay flat on an even surface, you may still fix a warped baking sheet.

Method 1

The simplest way to fix your warped baking sheet is through the towel method. After placing your warped baking sheet on a flat surface, lay a towel along the warped surface. The towel will serve as padding to incur additional damage. Next, warm your baking sheet for 7 to 10 minutes to prevent heat shock.

Use a rubber mallet and gently tap the warped baking sheet until it flattens. Do not hit the baking sheet hard, or it will leave dents that can further damage the baking sheet.

Method 2

The second method is through the wood method. The baking sheet will be heated until it is malleable. Then, instead of placing the woodblock while the baking sheet is heating, it will only be placed after the heating process. This method is better if the bumps are larger and requires harder hitting.

Place the heated baking sheet on the wooden block and strike it until it flattens. Do the same thing on the baking sheet’s other side if you feel it is still uneven.

Method 3

Locate a flat surface and lay down a towel flat on the surface. Then heat the warped baking sheet for 7 to 10 minutes on low to prevent heat shock. Next, place the baking sheet on the towel with the open side up when the cooking surface is warped upwarp or place the baking sheet upside down if the cooking surface is warped downward.

Check this too: How to Tell If a Pan is Oven Safe

What are the best baking sheets that don’t warp?

Nordic Ware Natural Aluminum Commercial Baking Sheets are the best quality brand for baking sheets. They come in various sizes, are made of pure aluminum that won’t rust, and the rims are reinforced with steel to prevent warping. You can bake with them at temperatures up to 450 degrees F.

Baking sheets will get used in the kitchen more often than we may realize. So quality is essential, and many baking sheets out there put a lot into making great bakeware.


  1. Ensure the baking sheet will fit in your oven. These recommended brands are half-size and should work in most home ovens.
  2. The color of the baking sheet affects baking. Darker color baking sheets heat faster and can cook foods quicker.
  3. Lighter color baking sheets such as aluminum will conduct heat equally throughout the baking sheet but may take a longer time browning certain foods.


The thicker the baking sheet, the less likely it is to warp. This is because they heat up more evenly compared to thinner baking sheets.