The photo above is capable of causing divorces, ending friendships, and starting wars. Think I'm joking? Then you've never talked to a no-soaper. All I'll say is this: Woe to you if you ever touch a no-soaper's cast iron pan with a sudsy sponge.
That's the nature of cast iron. Because it's one of the greatest pieces of cookware in the kitchen, and because it requires some special care, passions can run high. But the truth is that maintaining cast iron cookware isn't much of a chore at all, and many of the stricter rules that people insist on needn't be so strict.
Here's the skinny on taking care of your cast iron cookware so that it's always at its best, without any of the mumbo jumbo you're likely to encounter elsewhere.
Before We Begin
If your cast iron pan is new, you may need to give it an initial seasoning. It's an easy process, which you can read about in greater depth here. The main thing you need to know is that seasoning is a hard, protective coating on the pan that's created by rubbing the pan with oil and then heating it. When exposed to heat, each layer of oil transforms into an extremely thin, plastic-like coating. As those layers build up, the pan becomes increasingly protected against rusting (which, in its stripped-bare state, it will rapidly do just by sitting in the open air), while also developing the nonstick characteristics that make cast iron so useful.
Once you've established your initial layers of seasoning, the most important next step is to use your pan as often as you can, especially for anything that involves cooking with fat or oil: searing meats, frying bacon, sautéing vegetables, frying chicken, et cetera. With each use, you'll set down successive layers of seasoning that will only make your pan better and better.
And that's where the issue of cleaning comes in.
Cleaning Cast Iron
Let's start with a very basic premise that we can all agree on: A dirty cast iron pan needs to be cleaned. The question, then, is how. One of the most widespread beliefs is that you can't use soap, and the reason you'll usually be given for this is that soap is powerful enough to strip away the seasoning you've worked so hard to build up.
Soap is good at washing away grease and dirt, so perhaps it's understandable that people think it can also wash away seasoning, since the seasoning is essentially baked-on fat. But even though the seasoning started out as a fat, it's been so thoroughly transformed ("polymerized" is the technical word) that it's no longer at risk of being stripped away by a bit of soap, especially not the gentle modern soaps we work with today.
No, if you wanted to remove the seasoning, you'd need to either scour it with something very abrasive, like steel wool; heat it at a very high temperature for an extended period of time without any fat in it; soak it in a strong lye solution; or strip it via electrolysis. Suffice it to say, it takes quite a bit of effort to actually take the seasoning off a cast iron pan.
But soap? Soap ain't gonna do jack to that seasoning. We know, because we regularly wash our pans with soap at Serious Eats, and they're as beautifully seasoned as ever.
So grab your dish soap and a sponge, and let's get cleaning.
Step 1: Wash Well
Once you're done cooking in your pan, go ahead and wash it with some warm soapy water, wiping it with a kitchen sponge. If there are a few stubborn burnt-on bits, you'll be fine using the synthetic scrubber on the back of many kitchen sponges, as it's not as harsh as steel wool.
If, for some reason, you've scorched some nasty stuff into the pan, you can pour salt into it, set it over high heat, then rub the charred gunk out with some paper towels. The salt acts as an abrasive that's safe for the seasoning, while the heat can help carbonize any remaining bits of food, making them easier to scrub away. Then just rinse out the salt, wash the pan with warm soapy water, and continue to the next step.
Step 2: Dry Even Better
Water is the enemy of cast iron, so the last thing you want to do is leave it dripping wet post-wash. Sure, the seasoning will prevent any rust from forming right away, but if the pan is left to stand with water in it, even those tough layers of polymerized oil won't be enough to stop the relentless oxidative skirmish between iron and H2O.
So make sure to dry the pan thoroughly with towels right after washing. Even better, once you've hand-dried the pan as best you can, set it over a high flame. The heat will speed evaporation, driving off any last bit of moisture and guaranteeing that the pan is totally dry.
Step 3: Oil Lightly and Heat
The last step is to prime the pan for its next use by laying down one bonus layer of protective seasoning before putting it away. To do that, just rub the pan very lightly all over with an unsaturated cooking fat, like canola, vegetable, or corn oil, making sure to buff away any visible greasiness so that the cast iron almost doesn't look like you've oiled it at all.
Then put the pan back over a burner set to high heat, and leave it for a couple of minutes, until the pan is heated through all over and lightly smoking. You could do this in your oven for more even heating, à la the initial seasoning process, but I find that too cumbersome as part of a daily ritual; for just one quick final seasoning step, the stovetop works fine. (Note that if you rub the pan with oil and put it away without heating it, the oil can become sticky and rancid before the pan's next use, which is a real bummer. If you've accidentally let this happen, just wash out the pan with soap and water to get rid of the gunk, then dry it and heat it, and you should be good to go.)
And that's it—easy enough that anyone can do it, without resorting to fisticuffs.