What it is. Seasoning is what happens when fats are heated to a certain point that causes them to reorganize into something resembling a plastic coating and bond to the metal. That coating is smooth and slick, allowing for foods to easily release from the pan. Cast iron is “the original nonstick cookware,” says Mark Kelly, the public relations manager at Lodge, the brand synonymous with cast-iron cookware.
Often, the fats come from oils, although depending on what you use, anything from bacon fat to shortening can contribute to seasoning. I like this explanation from cookbook author Anne Byrn, from her recently released “Skillet Love”: “Oil is the best friend to the skillet. It keeps it protected, impervious to any moisture that might cause it to rust. Think of oil on a skillet like moisturizer on your skin. … Heat plus oil builds the patina and makes your skillet naturally nonstick.”
Most of the cast iron you buy comes preseasoned. That means you can start cooking in it right away.
To see whether your pan is well-seasoned, Cook’s Illustrated recommends this test: Heat 1 tablespoon of oil over medium heat in a skillet for 3 minutes and then fry an egg. If there’s no major sticking, your seasoning is good.
It improves with age. If you’re afraid of cooking in cast iron because you don’t want to mess up the seasoning, that’s the exact wrong approach. The more you cook in cast iron, the more seasoning will build up. It takes time, though. “It’s a natural process,” Kelly says. “You need to be patient.”
If you’re wondering whether vintage or newer-produced cast iron is better in terms of seasoning, it depends. Older pieces that have been used a lot and well cared for will have a superb established seasoning. But those heirloom skillets (and also some newer boutique brands) tend to be smoother than Lodge’s current more pebbly-surfaced cast iron. According to Byrn, “Lodge attests that the seasoning on the pan has a better chance to get into the crevices and form its own barrier against water if the surface isn’t smooth as glass.” That’s not to say you can’t season a smoother skillet, but you should be aware of the potential differences if it takes longer.
Maintain it. To maintain the seasoning, oil the pan after each use, returning it to the burner over medium-low heat after cleaning (see below) and then rubbing it down with oil and paper towels until it’s smooth and shiny with no visible residue. Kelly says you can do your coat of maintenance oil in a 200-degree oven for 15 to 20 minutes, too. As for what type of oil to use, Byrn recommends the least saturated options, including canola, corn, soybean, sunflower and flaxseed. Cook’s Illustrated’s top pick is flaxseed, because it is faster at creating a more durable seasoning. Sunflower and soybean oil (Lodge uses soybean on its cookware) are good, affordable options. If you prefer to use lard, Burn cautions to wipe off any excess on the surface so it doesn’t go rancid in your cabinet.
Even if you’re short on time and can’t reheat the pan, at the very least wipe on a thin layer of oil before you put the pan away, buffing it until no greasy spots remain.
Don’t be scared of ruining it. “A happy skillet is sitting at the back of the stove right now, cared for, talked about, needed,” Byrn writes. “But don’t get so obsessive about this process that you are fearful of using your skillet. There is a reason that iron skillets have survived the centuries. They withstand a little abuse but really appreciate being coddled, too.”
Some mild dish soap will not remove seasoning when cleaning. It’s also unlikely to be scratched or chipped off by metal utensils, since, as we’ve established, it’s chemically bonded to the cast iron. Moreover, contrary to what you may have been told, a well-seasoned pan can stand up to acidic foods such as tomato sauce, to a certain extent. To protect the seasoning and prevent metallic flavors in your food, Cook’s Illustrated recommends limiting the cook time for acidic foods to 30 minutes and then removing the food immediately. Serious Eats chief culinary adviser J. Kenji López-Alt also suggests staying away from cooking liquid-based dishes in cast iron until the seasoning is well-established.
But if you do damage it, all is not lost. As Kelly likes to say, “Leave no cast iron behind.” If your pieces have been damaged or neglected, or you salvage some that have been roughed up, “you can always resurrect them.” There are a variety of strategies for stripping and reseasoning cast iron. Choose what works best for you. When it comes to addressing small patches of rust, Kelly recommends using steel wool to rub it down before proceeding with reseasoning. Lodge’s preferred method is to rub the seasoning oil or melted vegetable shortening all over the pan and let it bake on the middle rack of the oven at 350 degrees for an hour, with a sheet of aluminum foil underneath to catch any drips. Repeat as necessary until the seasoning is where you want it to be. For her part, Byrn cranks the oven to 500 degrees, coats the skillet with a tablespoon of oil, wipes off the excess and bakes it upside down for an hour over foil.
If you have a truly abused skillet, you’ll need to start from scratch by stripping the seasoning and going through multiple rounds of restoring it. Again, strategies vary on how to strip seasoning, including using the self-cleaning feature of your oven. Cook’s Illustrated, though, prefers using a spray-on oven cleaner. Here’s its method, which involves rubber gloves and plenty of fresh air because oven cleaners are particularly powerful. For less intense situations, check out Lodge’s troubleshooting guide.
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