If you’re seeing rust spots, this might be why.

By Betty Gold
December 08, 2020
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For many home cooks, a cast iron pan is the single most precious piece of cookware in the kitchen. If so, it likely gets more use than any other cooking tool (aside from your beloved chef’s knife, of course). It makes sense—not only are cast iron pans just the thing for high-heat searing, baking, and shallow frying, but when properly maintained, these versatile workhorses will last you a lifetime.

This brings me to my next point, which is that there are a number of traits unique to cast iron cookware that, when understood, will help your prized pan live long enough to get passed along to your little ones someday. You’re likely already aware that cast iron needs to be seasoned and that it requires a different cleaning method than your illustrious stainless steel skillet, but trust me when I say this is just the start of getting to know your pan. The two of you have a long, fruitful relationship ahead—why not dig deeper? Here, seven common cast iron cookware mistakes you’ve been making, plus how to solve them.

This is easily the biggest, grossest, and most frequent mishap I see with cast iron use. Here’s the thing: The seasoning on your cast iron pan isn’t just a thin, baked-on layer of oil. It’s actually a layer of polymerized oil, which makes is (chemically speaking) more similar to plastic than grease. The seasoning is bonded to the surface of your pan, and there’s no way a couple drops of dish soap are going to remove that. Please, for the love of god, do not allow harmful bacteria from food to grow in your cast iron skillet. Soap, a soft sponge, and a bit of scrubbing is OK. If you need to remove burned-on food, you can also try scrubbing with a mild abrasive, like coarse salt, and/or a nonmetal brush (like this one from Lodge).

That being said, your cast iron should never be allowed to soak in water. The goal is to keep the amount of time your pan is wet as short as possible. Water is cast iron’s nemesis, so be sure to dry it thoroughly as soon as you’re finished cleaning to avoid rust spots popping up on the pan’s surface. Coating the pan with a small amount of oil after drying won’t hurt, either.  

You’ve likely heard that cooking with acidic ingredients is bad for cast iron—it reacts with the metal, which leeches into your food, and so on. You’re sort of right. As with the soap concept, cast iron is significantly sturdier than it gets credit for. If your cast iron is properly seasoned, the only thing your food should be interacting with is the polymerized oil on the surface of the pan. Bare metal, however, can certainly interact with acidic foods. While I wouldn’t recommend simmering a slow-to-cook Bolognese sauce in your cast iron skillet, I wouldn’t think twice about adding a squeeze of lemon juice to Brussels sprouts or adding a splash of wine to deglaze chicken thighs.

The seasoning is the secret sauce to your cast iron skillet—it’s what gives it nonstick properties, after all. You must work to maintain this coating. How? Give it a quick re-seasoning after each use. After gently washing with soap and water and giving it a thorough dry, coat the pan with a half teaspoon of neutral oil all over (a paper towel helps distribute) and place over high heat on the stovetop. Continue heating until you see a bit of smoke starting, then give it one more rubdown and let cool.  

Cast iron is prized for its ability to get hot and stay hot. For the same reason, you’ll need to apply a bit of patience in the process of getting it there. Let your pan preheat on the stove for several minutes—think up to 10—before you add your mushrooms or meatballs. Why? Because you want them to start frying (instead of soaking up your oil) as soon as you toss them in. To see if it’s hot enough, drop a fleck of water into the pan—if it sizzles and evaporates, your skillet’s all set to sear.

While cast iron is a master at heat retention, it’s a mistake to think that the surface heats evenly. Unlike aluminum clad stainless steel or anodized aluminum nonstick cookware, cast iron actually heats extremely unevenly. I recommend avoiding cast iron when making anything fragile that you want to cook super evenly, like delicate fish or crepes. To help it heat more evenly, you can move your skillet around on the cooktop as it preheats so the flame will eventually warm its entire surface.

Like I said, your pan is a lot tougher than you think. There’s a reason why these things get passed down from generation to generation! It’s very unlikely that you’ll scrape off the surface of a well-seasoned cast iron skillet with a metal spoon or spatula. If you notice black pieces flaking off, they’re most likely burnt bits of food from some past cooking adventure that you refused to use soap to clean up afterwards.