The Real Secret to Non-Stick Cast Iron
Think 2 words: hot and thin …
Both my grandmothers lived into their early nineties and cooked with cast iron into their eighties. My mother still uses her pans in her eighties. My father did until he couldn’t get around the kitchen anymore.
I inherited three cast iron pans from my grandparents — a flat #7 from sometime in the 1800s that’s good for heating tortillas and covering hot eyes, a #5 pan from the 1930s, and a #10 skillet from the ’50s. (The older pans’ numbers are the diameter of the stove ring they fit into, in inches. For the newer one, which would be a #9 in the ring system, it’s the diameter of the pan’s cooking surface.)
I also have a recently made Dutch oven. My grandmas’ Dutch ovens are with elder cousins somewhere, and good old ovens with lids ain’t cheap.
Everybody wants to know how to keep cast iron clean and non-stick. So let’s talk about how to wash and season it.
Seasoning versus grease
Just to get it out of the way, seasoning makes cast iron cookware non-stick, and you don’t get it by letting cooking-fat coagulate in the pan. Properly using a pan does keep it seasoned, but seasoning is polymerized oil bonded to the metal, not a coating of grease.
Just to keep an iron pan from rusting, you need to maintain some seasoning. To keep it non-stick you need a few microscopic layers of carbonized oil coating the iron. I’m going to assume you have pans that don’t need grinding or derusting and are ready to clean and season.
You’ll get best results with an unsaturated fat that’s liquid at room temperature like canola, which I use, or vegetable oil. Higher smoke-points are preferable. Flaxseed oil gives good results right away but it’s expensive and has a reputation for flaking.
Soap or salt
Depending on how you’re using it, you might just need to wipe a pan down to clean it. If nothing sticks to the hot pan, buffing the oil out is all you have to do. Wipe it out once while it’s still warm and again after it cools.
If the pan needs cleaning, you can use dish soap or coarse salt. Don’t worry, the soap won’t hurt the pan or wreck the seasoning. (Using lye soap these days? No? OK, you’re good.) Use hot water and a mild scrubbing sponge. You must dry it out completely, though.
Cheat: After washing, you can put the pan on a burner at high heat for a couple of minutes and drive off any lingering moisture, then give it a thin coat of oil while it’s hot and buff it out after it cools. And by “thin coat” I mean put the towel over the mouth of a typical bottle of canola oil, tip the bottle for a second, put it back upright. Just the oil on that towel should handle a whole skillet.
If you don’t want to worry about drying, don’t use soap and water at all. Instead, wipe the pan out, put it on a low burner and warm up a little oil and some coarse salt — I keep a box of kosher salt in the pantry just for this — and scrub the pan with a cloth or paper towel, then wipe it clean.
When and how to re-season
When you cook with oil on high heat, and you’re food’s not sticking, you’re maintaining that polymer layer. Which is why you always cook with oil or a melted fat in cast iron. (Some make an exception for bacon.)
New pans can usually benefit from a round or two of seasoning. Used pans should be cleaned and seasoned, unless they are known to you. A flaking pan needs to be scrubbed out and reseasoned. And of course, if food sticks, season. Some folks will re-season after cooking with acidic foods like tomatoes or wine.
Essentially you bake the cast iron at 450 F (230 C) for half an hour with a thin layer of oil on it. Wipe the whole pan down with a lightly oiled towel, either cloth or paper, then use a dry towel to remove the excess. (Leave too much behind and you’ll get tiny, hard polymer “beads” on the surface of your pan.)
Place the pan upside-down on a rack in the heated oven. Some people advise putting foil on a rack below the pan to catch any dripping oil. But if there’s any danger of oil dripping from your pan, get a dry towel and wipe it down until there’s not!
Naturally, this isn’t a chore for kids. These pans are very heavy and dangerously hot, so keep children and pets out of the kitchen during these next steps and until the iron has cooled. Oh, and you’ll need highly insulating pot holders that don’t have rubber gripping surfaces which the hot iron can destroy.
You might want to give new pans a couple of rounds, adding a new layer of oil between turns in the oven, applying it to the (very) hot pan. The cooking surface is more important after the first round. I’ll often use the second towel to add just a little oil to the exterior and handle after buffing out the interior. Take your time and be extremely careful, as 450-degree iron can cause severe injury if mishandled, or if you get distracted from what you’re doing.
A rehabbed pan might need as many as four rounds. Two or three should suit for fixing a sticky pan after a thorough cleaning. And a grace coat never hurts, after the final bake when it’s still hot.
Cheat: There’s a stripped-down method sometimes called a campfire season that’s often sufficient remedy for a pan that’s starting to stick. Or don’t wait till there’s a problem, give your iron a quick treatment once a month or so. Just add the very thin layer of oil and put the pan on a medium-high burner. At a certain point the oil should lightly, and briefly, smoke — that’s the polymerization. (Do not do this with a “wet” pan. It shouldn’t feel at all wet or oily or greasy to the touch.) When the smoking stops, remove the pan from the heat, give the cooking surface one more thin coat of oil, then buff it out again when it’s cool.
In a nutshell
Getting that super-thin microlayer of oil hot enough to polymerize is the secret to cast iron that cooks forever. Dish soap won’t strip it off once it’s on. And it’s not hard to maintain if you know what you’re trying to accomplish.
Of course, the best single thing you can do to keep your pans in shape is to cook with them. Mine live on the stovetop, except for the Dutch oven. They’re easy to use when kept handy.
Keep them clean, season as needed, and your pans will outlive you. That’s why you should cook with the younger generations, by the way. Because if no one wants your cast iron after you go, were you ever really here?
Read every story from Paul Thomas Zenki (and thousands of other writers on Medium).