Why Does Cast Iron Need to Be Heated Slowly? – 4 Things to Know

Who else is wondering, “Why does cast iron need to be heated slowly?”

I’m sure I’m not the only one who has heated their pan too quickly because they didn’t know it mattered.

It’s actually quite common for people not to know.

However, when your food doesn’t turn out the way you expect, you are left wondering what went wrong.

There’s usually a perfectly reasonable explanation.

And one such reason is you didn’t heat your pan slowly enough.

Allow me to explain.

Why Does Cast Iron Need to Be Heated Slowly?

The main reason cast iron needs to be heated slowly is that it doesn’t cook evenly when the pan gets hot too quickly. Instead, you get hotspots where your food cooks faster in some places than in others. And this results in over or undercooked food, sticking, and possibly burning. Another reason to avoid getting your pan hot too fast is that cast iron can warp.

1. Why You Need to Preheat Your Skillet

The first thing you need to know is that cast iron works best when you preheat it.

Preheating your pan allows you to start cooking your food right away.

Having a hot skillet is essential for a few reasons:

  1. For meats, it keeps the juices inside and creates a brown crust on the outside. When juices escape, your steak steams rather than sears. Plus, you get a dryer, tougher piece of meat, and the outside will take on a grayish color.
  2. When sauteing, starting with a heated pan will result in crispier, more colorful, and flavorful vegetables. When your pan isn’t hot enough, to begin with, you end up with mushy veggies that look dull and taste bland.
  3. Eggs also need to cook quickly, and when you start with a heated pan, the heat and the fat will keep them from sticking.

I will note that oil or fat is also needed when cooking meats or sauteing vegetables, and the pan and the oil both need to be hot.

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Cast Iron Skillet Hack

2. Preheat Slowly to Avoid Hotspots

The first reason to warm up your skillet slowly is to minimize hotspots when cooking.

Cast iron does not heat evenly, and its ability to transfer heat from one part of the pan to another is poor.

So, that means the skillet will naturally get hotter where the burner’s flamer hits the pan.

In other words, hotspots.

Interestingly, as I was reading about this subject on a forum, someone was having problems with hotspots and wanted advice.

One person pointed out that cast iron cookware doesn’t perform well on low BTU output residential stoves.

That’s because the edges of the pan will never get hot enough.

Therefore, to some extent, you will always have hotspots when cooking from home.

However, when you slowly get the pan hot, you give the heat more time to travel to the edges, and you’ll have your best chance of even cooking.

Or better yet, preheat your skillet in the oven.

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3. Preheat Slowly to Avoid Warping

A second reason to preheat slowly is so you don’t accidentally warp your pan.

Cast iron warps through improper rapid heating or cooling, also known as thermal shock.

Clearly, you wouldn’t want to leave an empty skillet on a burner set at high heat for a long time because the pan has nothing to absorb and distribute the heat.

Remember, cast iron doesn’t heat evenly but gets hotter where the flame hits the pan.

And wherever the flame hits, the metal expands more rapidly and can potentially warp.

Now, on the same forum where the person talked about cast iron not performing well on residential stoves, this person also said it’s highly unlikely cast iron would warp from home use.

At least not from heating on your low BTU stovetop.

On the other hand, it could warp if you put your hot pan in cold water.

So, don’t ever do that!

Extreme temperature changes do cause cast iron to warp or crack.

From personal experience, I have had hotspots, but not a warped pan.

However, I think if you wanted to heat your skillet quickly, so you put it on high heat and then forgot about it, it could happen.

Yes, even in your own kitchen.

Of course, no one would do that on purpose, but that doesn’t mean it hasn’t happened.

How to Test For a Warped Cast Iron Skillet

4. How Long Does It Take to Heat Cast Iron?

I’m not sure I can tell you the exact amount of time you should heat your cast iron because many opinions are out there.

I usually preheat my skillet anywhere from 3-5 minutes, and a bit longer when searing a steak, but others will say 5-10 minutes minimum.

They say it takes that long for the heat to reach the edges of the pan and give you the most even-temperatured surface for cooking.

Regardless of how long you preheat your skillet, what’s important is to take your time heating it rather than cranking the burner on high so you can start cooking faster.

Because heating your cast iron too quickly will lead to uneven cooking or sticking.

Or worse yet, warp your pan.

I didn’t know any of these things when I first started.

Therefore, I was heating my pan on high heat because it made sense to me.

Fortunately, my pan didn’t warp.

However, I did experience some of the other problems, especially with my bacon sticking and cooking unevenly.

And then my eggs would stick.

Now I know to preheat slowly and give it time.

And for the most part, the bacon and eggs turn out just the way we like it.

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Preheating Cast Iron Pans

Final Thoughts

So, if you asked, “Why does cast iron need to be heated slowly?” you can see there are two very good reasons why.

Heating slowly is the best way for cast iron to heat more evenly, and avoid hotspots that cause uneven cooking.

In addition, high heat can potentially lead to your pan getting warped.

Since, neither hotspots nor a warped pan is desirable, it makes sense that you would heat your pan slowly.

Finally, it doesn’t mean you have to preheat it on low; most people recommend low to medium.

Have you had problems with hotspots or a warped pan?

Tell me about it in the comments.

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