The dos and don’ts of removing rust stains from your cast-iron skillet.
Q: I have a cast-iron skillet that I have been using for a few years. It has brown, rust-coloured stains that don’t come off, no matter what I do. I’ve tried kosher salt and a small chain, soap, a power washer. Nothing works. Or is there a way to fix this?
A: Yes, you should be able to remove even stubborn rust from your cast-iron skillet.
Most nonstick pans have a coating that gradually wears or chips away. Once that happens, which might be in just a few years, there is no way to restore the coating. You need a new pan.
But a cast-iron skillet is the same material all the way through, other than a surface coating of what’s called “seasoning” — multiple layers of baked-on oil, which you apply yourself and can reapply later as needed. So you can remove surface crud, whether it’s rust or a bumpy layer of food left from inadequate cleaning after multiple meals, and get down to bare metal. Then you can start over to build up a few layers of oil, which will make the pan close to nonstick. Because a mistreated cast-iron pot can be made good as new, one you get today will last the rest of your life – and be worth passing on to the next generation.
Lodge Cast Iron, a fifth-generation family company that’s been making this kind of cookware since 1896, shared some tips for removing the stains:
- Start by scrubbing aggressively to remove the rust. Use warm, soapy water and a metal scouring pad, or augment the pad by using the Lodge rust eraser. Made of silicon carbide (an abrasive often used in sandpaper) embedded in rubber, it takes off thick rust fairly quickly.
- You could even use sandpaper, as long as you sand by hand, said a Lodge customer service representative who identified herself as Kelly. She recommended against using anything in a machine – such as a wire brush in a grinder, featured in at least one YouTube video. Power sanding or grinding might get the metal too smooth. “If you get the pan too smooth, the seasoning won’t stick to it,” she said. “It will ruin the pan.”
- Don’t use heat. You may find advice online about using a propane torch or tossing a pan in a campfire to burn off rust or carbon deposits. Lodge doesn’t recommend using heat, Kelly said, because it could warp or crack the metal if the heat is uneven or too hot.
- Instead, try pouring some water into the pan and warming it on low to medium heat, which won’t hurt the skillet and could make cleaning baked-on food easier. Use a spatula to scrape off the deposits as they heat and soften. Just don’t walk away and let the water evaporate while the burner is on.
- Many websites suggest removing rust by soaking a skillet in white vinegar for 30 minutes to two hours. “We don’t have written recommendations about that,” Kelly said, “but people certainly do that.” She didn’t offer any warnings against it.
Whichever of these strategies you use, you might still see remnants of orange rust after you’ve scrubbed, rinsed and dried the pan. That sometimes happens when a pan is left hanging for years in a damp place where rust works deep into the metal, Kelly said. But that’s not really a problem. You can just move on to the seasoning steps. The remnants of rust will become embedded in the first layer of oil, but they will be topped by additional layers of oil that are rust-free. “The molecules melt together and form a sea of baked-on oil over the raw pan,” Kelly said.
To season the pan:
- Start by applying a thin layer of oil with a paper towel. The website of America’s Test Kitchen recommends flaxseed oil, which it says oxidises and polymerises into a durable coating faster than other vegetable oils. But it says cheaper oils, such as sunflower, soybean, corn or canola, also work. Don’t use olive oil or bacon fat.
- Bake on the oil in an oven set to 230C to 260C.Lodge recommends placing the pan upside down on the top rack and lining the bottom rack with aluminium foil to catch drips. Bake for an hour, then let the pan cool.
- Repeat a few times to build up the oil layer. Even five or six coats would be good. When you’re done, the seasoning should look black, without a trace of rust. Lodge says oven seasoning is the best method when you’re restoring a pan that was heavily rusted.
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Advertise with NZME.Or try doing it on the stovetop. America’s Test Kitchen recommends the same time and temperature for baking the oil in an oven but also suggests a stovetop method. Heat the skillet over medium-high heat, then, using tongs and keeping the pan on the heat, rub with a paper towel moistened with 2 tablespoons of oil until the oil smokes and you don’t see any oil in the pan. Let the pan cool. Repeat multiple times, making sure the oil smokes each time. The smoking stage is when the oil polymerises, or turns into a film that resembles a plastic coating.
Then maintain the seasoning as you cook meals:
- Preheat the pan on a medium setting as you prepare to cook. Add a little oil and then butter, if you want to use butter, before you add food. Cook as you would with any nonstick pan.
- Let the pan cool before you wash it. But it’s fine to wipe out oil and food with a paper towel while the pan is still warm.
- When the pan is cool, rinse it with water and use a plastic pan scraper to remove cooked-on deposits. Many people just use water, without using soap. But using a little hand dishwashing soap, such as Dawn, is also fine, Kelly said. “Back in the day, people didn’t use soap because soap contained lye, which will strip the seasoning,” she said. “But soap like Dawn is mild and gentle.” If it did strip seasoning, people who run businesses devoted to restoring cast iron would just use soap to strip, she noted.
Dry the skillet after you wash it, then warm it over medium-low heat. You will see the colour change slightly as remnants of moisture evaporate.
When the moisture is completely gone rub about a half teaspoon of oil over the pan with a paper towel. Rub until no oil residue remains. Rubbing on the oil is especially useful after cooking acidic food, which can eat into the seasoning, or using the skillet on especially high heat.
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