They say a cast iron skillet is the only skillet you’ll ever need. But they’re lying.

The truth is that you can do without a cast iron skillet, especially if you’re looking for a frying pan that’s easy to lift and carry around, doesn’t need to be seasoned, is suitable for cooking highly acidic foods, and can be go in the dishwasher. (We will get to all of these in a minute.)

And yet, a cast iron skillet will cook a steak with the crispiest, most flavorful crust like no other. It moves freely from stovetop to oven and can even be used under the broiler or on the grill—which, apart from stainless and carbon steel, is more than can be said for its ceramic and non-stick counterparts.

These skillets aren’t for everyone, that’s for sure. And they require their fair share of care and prudence when cooked with. However, there’s good reason why, centuries after they were first invented, cast iron vessels remain staples in the American kitchen: their price, sturdiness, and versatility cannot be rivaled.

Why Do Cast Iron Skillets Have to Be Seasoned?

Without the seasoning, a cast iron skillet will corrode and rust.

Cast iron skillets are single-piece cooking vessels made out of bare, uncoated iron. That iron is reactive: it reacts with the oxygen in the air and the humidity in your kitchen, as well as the foods you fry and the cooking liquids you simmer in it.

You season your skillet to protect it against corrosion and rust, and you shouldn’t use it to prepare recipes that call for wine, vinegar, tomatoes, and lemon juice, particularly when long simmering times are involved. Otherwise, the acidity level can damage the seasoning and cause it to start flaking off.

To season a cast iron skillet, you rub a thin layer of cooking oil all over the cooking surface, underside, and handles. Then, you bake the skillet upside-down in a 450°F oven for 1 hour. (The flip is required to prevent oil from pooling in the pan.)

The result is a patina of polymerized oil that’s bonded molecularly to the surface—protecting the metal from corrosion and rust and preventing foods from sticking to the bottom and sides. As you cook hearty foods in your skillet, the fat that melts and drips down from them builds its seasoning up.

What Makes Cast Iron So Good for Preparing Steak?

Cast iron doesn’t heat quickly, nor does it heat evenly. So why does everyone keep raving on about its ability to sear a steak?

Compared to other metals, cast iron is a poor conductor of heat. Its thermal conductivity is 52 Watts per meter-Kelvin (W/m K), as opposed to 54 W/m K for carbon steel, 237 W/m K for aluminum, and 413 W/m K for copper.

This, in case you’ve ever wondered, is the main reason why copper and aluminum frying pans preheat in as little as 20-30 seconds, whereas cast iron skillets and grill pans need 4-5 minutes on the stove to get up to heat.

Ironically, cast iron’s unwillingness to conduct heat is also what makes it such good cookware for preparing certain types of foods.

Slap a thick-cut steak, a juicy burger, or a hefty fillet of salmon on any other type of pan, and the cooking surface will almost immediately drop temperature from coming into contact with the room-temperature protein.

This has important implications for the results of your cooking. If you want to form a crispy, browned, caramelized crust on the outside of your food, then it is counterproductive for your skillet to lose heat the moment you put food in it.

As the cooking vessel recovers, the steak, in the case of searing, or the mushrooms, in the case of sautéing, will release liquid. Instead of evaporating, that liquid will pool in the pan and make your protein or vegetable soggy.

If you’ve ever tried to sear or sauté over too low of a heat, you know exactly what I’m talking about.

The same can’t be said for cast iron.

A cast iron skillet is capable of retaining a lot of heat. In fact, cast iron is as reluctant to let go of heat as it is to accumulate it in the first place. This makes the cooking temperature of these vessels slow to change (they take a while to heat up and as much to cool down).

Simply put, the cooking temperature of a cast iron skillet is very steady. This steadiness makes cast iron skillets the kings of searing steak and baking cornbread compared to all other cookware on the market.

Can Cast Iron Skillets Be Washed With Soap?

A cast iron skillet should never, ever go into the dishwasher. So can you at least wash yours with soap?

Much has been said and written about cleaning cast iron skillets with soap. And for good reason: in the 20th century, the lye used to make soap was obtained by boiling hardwood ash. The resulting caustic soda (lye) was so aggressive, it could eat away at all organic matter, including the seasoning on cast iron cookware.

For better or worse, this is no longer the case today. Nowadays, caustic soda is made by a chlor-alkali process, the same form of electrolysis that’s used to make chlorine at a commercial scale.

The lye in your dish soap is much milder than the lye in the dish soap our parents and grandparents used. For the same reasons, you can wash your cast iron skillet with soapy water without inflicting any damage to the seasoning whatsoever.

The Bottom Line

At the end of the day, the type of cookware that you use boils down to your budget, lifestyle, and preferences. Cast iron is low-cost, requires care, and is best for fatty meats and shallow-fried vegetables.

If you make bacon, sear steak, cook burgers, prepare sausage, and fry schnitzels; make French fries, cook hash browns, and do latkes; or bake cornbread and pizza pies often, then by all means, consider owning a cast iron skillet.

Just remember that these heavy-bottomed and thick-walled skillets need to be seasoned, must never be loaded in the dishwasher, and are not meant for every food. In particular, they should seldom be used for boiling liquids or simmering highly acidic foods.