Why Do Pans and Baking Sheets Warp? 6 Common Causes (and How to Unwarp)

Warping most commonly occurs with baking sheets and frying pans, but it can happen with any type of cookware. A wobbly, warped pan is annoying, unsafe and won’t heat evenly since the bottom doesn’t sit flat on a cooktop or oven rack.

The best way to keep your cookware from warping is to understand why it happens.

So, why do pans warp?

When a pan is heated or cooled rapidly, some parts expand or contract faster than others. The uneven expansion and contraction are what result in warping. Warping can occur from rinsing a hot pan in cold water, overheating, or a mismatch between the pan and the burner’s size.

Here’s the science behind it…

The Kinetic Theory of Matter states that all matter (including pans) is made up of atoms that are constantly in motion. When a pan is heated, its atoms vibrate more quickly, which increases the amount of space between them and forces the pan to expand. Conversely, when a pan cools down, the movement of its atoms slows down, they require less space, and the pan contracts.

Now you know why pans warp, but what you can do to prevent it from happening?

The best way to prevent pans from warping is to avoid exposure to rapid changes in temperature. Rinsing hot pans in cold water is the leading cause of warping, but there are several other causes.

In the following sections of this article, I dive deep into the six most common causes of warped pans and explain what you can do to prevent it from happening. I also reveal which type of pans and materials are the most and the least likely to warp.

If your pans are already warped, no problem. Towards the end, I explain, step-by-step, two simple methods you can use to repair pans that are already warped.

Use the links below to navigate.

• Cause #1: Rinsing Hot Pans With Cold Water
• Cause #2: Overheating
• Cause #3: Pan Is Too Big for the Burner
• Cause #4: Pan Is Too Thin
• Cause #5: Aluminum Pans Warps More Easily Than Steel Pans
• Cause #6: Single-Ply Cookware Is More Likely to Warp Than Multi-Ply Cookware
• How to Fix a Warped Pan (2 Easy Methods)

Why Pans Warp: The 6 Most Common Causes

As I explained upfront, the molecular structure of pans is altered when they become exposed to rapid changes in temperature (energy), which causes uneven expansion and contraction.

But, if you buy good quality pans and use them properly, you’ll never have to worry about warping.

Below is an overview of the six most common causes of warped pans. Once you understand these causes, you’ll easily be able to avoid the mistakes that can ruin cookware.

Cause #1: Rinsing Hot Pans With Cold Water

Rinsing pans with cold water while they’re still piping hot is the most common cause of warping.

Although it’s tempting to cool down and clean your pans immediately after cooking, do NOT rinse or soak them in cold water while they’re still hot. Doing so will result in Thermal Shock, which is when an object is exposed to a rapid change in temperature, causing it to expand or contract unevenly. When the stress, or shock, is stronger than the material, it causes cracking, deformation, and warping.

An everyday example of Thermal Shock is when you put an ice cube in a warm glass of water. Almost immediately, the ice cube makes a popping sound and cracks. Cracking occurs because the outside layer of the ice cube warms up and expands much faster than its core.

The same thing happens with cookware.

When cold water comes into sudden contact with one side of a hot pan, the atoms of the pan rapidly and unevenly contract, which causes warping. When a pan cools down more gradually, it’s less likely to warp because its atoms contract evenly across the entire pan.

Warping due to Thermal Shock occurs so often that almost all cookware manufacturers explicitly warn customers not to expose a hot pan to cold water.

Calphalon, one of the top U.S. cookware companies, has this warning in their use and care instructions: Allow pans to cool completely before washing. Never immerse a hot pan in cold water, as this will cause irreparable warping.

Cuisinart, another well-known cookware maker, provides similar advice in their use and care guide: Before you place the pan in water, allow it to cool. Placing a hot pan in cooler water can warp the pan.

Cookware companies are not only warning customers about Thermal Shock, but they’re also making it clear in their warranties that you’re not covered if your pans warp from Thermal Shock.

All-Clad’s warranty states: This warranty does not cover damage arising from thermal shocks, drops, improper use, failure to follow the use and care instructions, or unauthorized modification or repair.

So, how can you avoid Thermal Shock and prevent your pans from warping?

Instead of rinsing your hot pan with cold water, let the pan cool down for 10 to 15 minutes, then wash it with warm water.

When deglazing a pan, turn the temperature of the stove to medium or lower, use room-temperature deglazing liquid (wine, broth, water), and only pour a small amount in the pan at a time.

Cause #2: Overheating

Cooking with extremely high temperatures is the number two most common cause of warped pans, and the science behind it is the same as Cause #1 (Thermal Shock).

When an overheated pan comes into contact with a piece of cold meat, water, or deglazing liquids, it’s much more likely to warp than a pan heated on medium because the difference in temperature between the pan and the cold items is more significant.

Even if a piping hot pan is left to cool down on its own, sometimes the difference in temperature between the pan and the cool air can be enough to cause warping.

Additionally, an overheated pan doesn’t need to come into contact with something cold to become warped. It can warp by merely heating up too fast.

A room temperature pan put on a burner set to high or an oven preheated to 450 degrees Fahrenheit or greater can expand too quickly in some areas while remaining unchanged in others. When this happens, the stress of the temperature change (Thermal Shock) causes the pan to expand unevenly and warp.

Good quality cookware is crafted to conduct and retain heat efficiently. If you give the pan time to preheat, medium to high heat is almost always hot enough, especially if your cooking with well-constructed pans. 

In their usage instructions, both All-Clad and Calphalon advise that you should only use high heat for boiling water (All-Clad usage instructions, Calphalon usage instructions).

For meals that require browning or searing on high heat, bring the meat to room temperature before placing it on the pan to minimize the difference in temperature between the pan and the meat.

Cause #3: Pan Is Too Big for the Burner

Although less common, another cause of warping is a mismatch between the size of the pan and the burner.

When you place a large pan on a small burner, only a small section in the center of the pan touches the heat source. If the heat is too high, the part of the pan exposed to the heat source will expand and contract before the rest of the pan is affected.

When one small section expands or contracts while the sides/edges stay the same, the expanding or contracting section can’t expand outward or inward, it can only expand up or down. This uneven expansion leads to the bottom of the pan either warping downward or upward.

A simple solution is to only use large pans on large burners and small pans on small burners. If, for some reason, none of your burners are big enough for your pan, use extra caution and heat the pan slowly, so the entire piece heats up more evenly.

Cause #4: Pan Is Too Thin

Pans with thin walls are much more likely to warp than thick pans, for a couple of reasons.

First, when exposed to rapid temperature changes, thick pans do a better job absorbing the expansion and contraction within its walls. On the other hand, thin pans have less material, so their shape is more likely to change when they expand.

Secondly, thick pans conduct heat more evenly than thin pans, and, as we know, uneven heating and cooling causes warping.

According to LifeHacker.com, pans are constantly losing heat into the air, and thinner pans lose heat faster than thick pans. This means that thin pans often have hot and cold spots and are less likely to maintain the same temperature throughout. The result, warping.

This problem relates to all types of cookware but is even more common with thin baking sheets. Have you ever opened up your oven to check on your meal and the pan looks like this:

Most home cooks have a few cheap and thin baking sheets for everyday baking and roasting. Warping is almost unavoidable with thin baking sheets. When the pan is warped and doesn’t sit flat on the oven rack, the food doesn’t cook completely even. This isn’t usually a huge issue, but it becomes more problematic when baking cookies or other delicate foods.

The solution: buy high-quality pans like these from Nordic Ware (link to Amazon) or search online for thick pans from any other brand.

You’re probably wondering, what is the threshold for a pan to be considered thick or thin?

If you’re concerned about warping, always buy pans that are at least 2.5 mm thick. Anything less is too thin and susceptible to warping. The thickness is not always published online, so you may have to contact the manufacturer before you buy.

Another way of determining the relative thickness of a pan is to compare the weight between several options with the same dimensions. Most of the time, a thick pan will be significantly heavier than a thin one.

In general, almost all pans made by high-quality brands like All-Clad (All-Clad on Amazon and All-Clad.com) and Calphalon (Calphalon on Amazon) are 2.5 mm thick or greater. It’s the cheap, no-name brands that you find in the department store that are most likely to warp.

Cause #5: Aluminum Pans Warps More Easily Than Steel Pans

Pans made with softer materials like aluminum and copper are much more likely to warp than pans made with stainless steel, which is extremely hard and durable.

Since the molecular structure of softer materials like aluminum and copper is not as tight as hard materials, they become more affected by rapid changes in temperature. In other words, they expand and contract more easily.

Also, aluminum and copper conduct heat much faster but don’t retain it as well as steel. In other words, aluminum and copper pans heat up and cool down very quickly. A quick response is helpful when you’re cooking meals that require precise temperature control, but it’s a recipe for warping if you’re not careful about avoiding Thermal Shock.

To dig deeper into the idea that aluminum pans warp more easily than stainless steel pans, I analyzed over 10,000 customer reviews on Amazon, Macys.com, and BedBathandBeyond.com for both aluminum and stainless steel frying pans.

To keep the analysis as fair as possible, I looked at cookware from the same brand, T-fal. T-fal has been in the cookware business for decades and makes cookware out of several different types of materials, including steel, aluminum, and hard-anodized aluminum.

As I analyzed each customer review, I made a note of every customer that complained about their cookware warping to understand which materials had a higher percentage of complaints.

Out of over 6K reviews of T-fal aluminum cookware, 3.4% contained complaints about warping while only .65% of reviews of T-fal stainless steel cookware contained complaints about warping.

Although I didn’t conduct a perfectly clean scientific experiment, this anecdotal data supports the hypothesis that aluminum cookware is more likely to warp than stainless steel.

So what does this mean for you? Should you avoid aluminum cookware and only buy stainless steel? Absolutely not.

All aluminum cookware isn’t destined to warp, and stainless steel cookware isn’t completely immune to warping. All this means is that you need to be extra careful to avoid rapid temperature changes with aluminum cookware.

Since almost all non-stick cookware is made from aluminum, there’s practically no way to avoid it. If you’re in the market for a new non-stick pan, I highly recommend choosing cookware made from hard-anodized aluminum.

Aluminum becomes hard-anodized through an electrolytic process in which raw aluminum is treated to thicken and harden its natural exterior, which makes it super durable and warp-resistant.

To compare regular aluminum cookware and hard-anodized aluminum cookware, I did the same analysis with T-fal hard-anodized aluminum cookware. I found that out of 3,250 reviews, only .86% of customers complained about warping. A nice improvement over regular aluminum, but a slightly higher percentage of complaints compared to stainless steel.

If you’re looking for new non-stick cookware, All-Clad and Calphalon both make high-quality hard-anodized aluminum sets that are incredibly durable and warp-resistant. You can check out those sets on Amazon (link to All-Clad, link to Calphalon), or you can learn more about these two brands in our recent head-to-head comparison of All-Clad vs. Calphalon.

Cause #6: Single-Ply Cookware Is More Likely to Warp Than Multi-Ply Cookware

Certain stainless steel cookware collections are constructed with multiple layers of metals bonded together. Cookware construction this way is considered multi-ply. Cookware that’s constructed with only one material is single-ply.

Multi-ply cookware has the best of both worlds—a core layer of a conductive material such as aluminum or copper that spreads heat evenly throughout the entire cookware, and an ultra-hard stainless steel exterior that retains heat for long periods. This combination of even heat conduction and long-lasting heat retention is what makes this type of cookware extremely resistant to warping.

All-Clad invented multi-ply cookware in the 1970s and remains the leader in the category. If you can afford it, I highly recommend checking out their cookware on Amazon or All-Clad.com.  

Single-ply aluminum and stainless steel cookware is more likely to warp, but the reasons differ by the material.

Single-ply aluminum cookware is more likely to warp because it doesn’t have a hard warp-resistant exterior. Also, aluminum heats ups fast but doesn’t hold its temperature for long periods, so there’s often an uneven distribution of heat, which causes uneven expansion and contraction.

Although steel won’t warp easily, a single-ply stainless steel pan is more likely to warp than a multi-ply stainless steel pan. Steel doesn’t conduct heat as evenly as aluminum, so when you put a single-ply stainless steel pan without an aluminum core on the stove, the heat doesn’t spread evenly throughout the pan. When high heat is concentrated for long periods in one area of the pan (likely the center), it can lead to uneven expansion, uneven contraction, and warping.

How to Fix a Warped Pan (2 Easy Methods)

Now you know how to prevent pans from warping, but how do you fix a pan that’s already warped?

The easiest option is to throw a warped pan in the trash and buy a new one. If it’s a cheap pan and you can afford a new one, I’d chalk it up as a learning experience and make sure it never happens again.

However, before you scrap it, check the warranty. Most manufacturers don’t cover warping since it’s almost always a result of misuse, but some do so it’s worth checking.

If it’s an expensive pan or one that you’re not ready to part with quite yet, there are two methods you can try to restore it to its original shape; the Towel Method and the Wood Block Method.

The Towel Method

The Towel Method is the simplest way to fix a warped pan and is best used when warping is minimal.

• Step 1: First, find a flat and hard surface. The best surface is a workbench, stone bench, or concrete floor.
• Step 2: Lay a towel flat on your surface of choice. This towel will serve as padding, so your pan doesn’t incur additional damage during this process.
• Step 3: Heat the pan on low for 7 to 10 minutes. A warm pan is easier to manipulate than one that’s cold and hard.
• Step 4: If the cooking surface is warping upward (toward the ceiling), place the pan on the towel the same way you’d place it on the stove.  If the cooking surface is warped downward (like a bowl), place the pan on the towel face down.
• Step 5: Place another towel over the upwards facing side of the pan to protect it.
• Step 6: Gently tap the warped part of the pan with a hammer or mallet until it’s restored to its original shape. Increase the pressure if it’s not budging. You may have to flip the pan over and tap on the other side for a few minutes to get it just right.

The Wood Block Method

For severely warped pans, the Wood Block Method is the best approach.

The first four steps of the Wood Block Method are the same at the Towel Method.

• Step 1: Locate a flat surface.
• Step 2: Lay down a towel flat on the surface.
• Step 3: Heat the warped pan for 7 to 10 minutes on low.
• Step 4: Place the pan on the towel with the open side up when the cooking surface is warped upwarp or place the pan upside down if the cooking surface is warped downward.

Here is where the Wood Block Method differs.

• Step 5: Instead of using a second towel, place a flat wooden block over the warped part of the pan. A 2×4 wood stud is ideal. Cut the 2×4 down so that it fits within the walls of the pan and sits flat on the cooking surface.
• Step 6: Forcefully hit the wooden block with a hammer or mallet until the pan falls back into shape. The wooden block spreads the force of the hammer evenly across the pan so that it flattens the entire surface. You may need to hit different parts of the block to smooth everything out.
• Step 7: Adjust the block until the entire pan is back into its original shape. Flip the pan over and hit the block on the other side if you overdid it on the first side.

Final Thoughts

When it comes to warped pans, the most important thing to remember is that warping occurs when the cookware is exposed to rapid changes in temperature.

Additionally, thin, single-ply pans made with soft metals like aluminum and copper are more likely to warp than thick, multi-ply pans made with hard metals like steel and hard-anodized aluminum.

If you can afford it, brands like Calphalon and All-Clad offer some of the most warp-resistant cookware you can buy. Both are available on Amazon and, to save you some time, I’ve linked to their most popular non-stick and stainless steel collections below.

Non-Stick:

• Calphalon Contemporary Hard-Anodized Aluminum Nonstick
• All-Clad HA1 Hard-Anodized Aluminum Nonstick

Stainless Steel:

• Calphalon Tri-Ply Stainless Steel Cookware Set
• All-Clad D3 Tri-Ply Stainless Steel Cookware Set

It’s possible to fix a pan that is already warped; however, a pan that warps once is more likely to warp again in the future. This is because the metal is weakened when its molecular structure is compromised, and it will never be as strong as it was before becoming warped.

A warped pan isn’t the end of the world. If the Towel or Wood Block methods don’t do the trick, keep in mind the six common causes of warped pans to avoid it from ever happening again.

Why Did Your Pans Warp?

Which of the six causes is the reason your pans are warped? Do you often rinse your pans under cold water while they are still hot? Do you cook on high heat regularly? Are your pans too big for your burners? Have you had good or bad luck with certain cookware brands?

In the comment below, let us know your experience with warped pans and what you did to fix it or prevent it in the future.

If you found this article helpful, you should also check out:

• Carbon Steel vs. Stainless Steel Pans: What’s the Difference?
• Cast Iron vs. Stainless Steel Cookware: What’s the Difference?
• Stainless Steel vs. Non-Stick Cookware: What’s the Difference?
• How to Make Any Type of Pan Non-Stick (Step-by-Step)
• How Long Do Stainless Steel Pans Last? (When to Replace Your Pan)
• Average Cast Iron Skillet Weight (With 17 Examples)
• What Size Sauté Pan Should You Buy? (Quick Guide)
• Carbon Steel Cookware Pros and Cons: 17 Things to Know
• Ceramic vs. Teflon Cookware: What’s the Difference?
• All-Clad vs. Calphalon: Non-Stick and Stainless Cookware Compared
• All-Clad HA1 vs. B1: Which All-Clad Non-Stick Collection Is Better?
• Is All-Clad Cookware Worth The High Price? An In-Depth Review
• All-Clad vs. Cuisinart: Is All-Clad Is Worth the High Price?
• T-fal vs. Calphalon: In-Depth Cookware Comparison
• All-Clad D5 vs. Copper Core: How Do They Compare?
• Is Farberware a Good Cookware Brand? An In-Depth Review