Cast Iron Pan over a Gas Flame

Cast Iron Pans: The Truth about Seasoning (and How to Do It)

So you bought yourself a cast iron pan. And you want to cook with it. And you’re scared of the mess. Well, don’t fry up your over-easy eggs just yet. You’re not ready.

First you have to season your pan — but let me explain what that means. I’m not talking about going through the motions, baking it once or twice with a film of oil and calling it seasoned. The pan doesn’t care what you call it.

Seasoning, rather, is the process by which you add a layer of fat, heat it until it hardens (polymerizes), and repeat — over, and over, and over, and over, and over. Seasoning is a cumulative process. Because each individual layer of fat is extremely thin, you won’t get a nonstick surface until you’ve added lots of layers. But if you keep at it, eventually those layers will build up to a remarkably hard, beautifully glassy, strangely resilient surface, which your over-easy egg will honest to God slide right off of.

That just doesn’t happen in one oven session. So here’s how it does happen.

Seasoning 101 (Getting Started)

First off, you’ll need some flaxseed oil.

This is the only edible oil which actually (scientifically) polymerizes when heated. Note: there are better-tasting things, so don’t feel obliged to use flaxseed oil every time you cook. But when you need to thicken up your pan’s seasoning, it’s the best.

1. Put the pan on the stove, medium heat.

2. Squirt in some flaxseed oil. Spread it around with a flat, metal spatula.

3. When you see the oil starting to respond to the heat (it looks kind of curly … or something) take a clean cloth and firmly rub it into the bottom and sides of the pan.

4. Squirt some more oil in. Spread it around. Let it warm up. Then rub it in.

5. Repeat as many times as you find this interesting.

6. Later, when you think of it, come back and do it again.

All right, so why does the spatula have to be flat and metal? Scraping the pan evenly while you’re heating the fat forms a smooth cooking surface. Even a machined pan has microscopic bumps and jags in the metal, and when you’re building lots of glass-hard layers of fat on top of that, you don’t want them to exaggerate that unevenness.

No, you want to plane it. Plane your pan. That’s what the spatula is for, and that’s why it needs to be metal (hard enough to shape the polymerizing fat) and flat (like you want the bottom of your pan to be). Rounded corners are important too, because a spatula that’s flat with rounded corners happens to be the same shape as the bottom and sides of your pan. Use something like this one.

Once your pan is nonstick, you can use a different spatula if you wish. I’ve got a wooden one that does fine. But the flat metal one is the only one that’s going to plane your cook surface as you use it.

Seasoning 202 (Let’s Cook Something)

Once you’re tired of the flaxseed oil routine, it’s time to try to cook. Cooking is, in itself, a way to season a pan. Every time you cook, you’re adding a new layer of fat. But to spare yourself grief and rage, you need to start by cooking the right things.

You want foods that benefit from lots and lots of fat, that cook very slowly, and that aren’t likely to stick. In other words? You want caramelized onions.

1. Add a huge block of butter (1-2 T.) to the pan on low heat, and let it melt. (If you’re not into butter, use some other kind of fat.)

2. Add an onion, diced. Toss it in the butter until all the pieces are coated.

3. Adjust the heat until you can just barely hear them cooking. Get it as low as possible without losing that sound. Resist the urge to turn up the heat: you are not browning or sautéeing these onions. No crispy edges!

4. Using a flat, metal spatula, stir the onions, firmly scraping the bottom of the pan, every 5 to 15 minutes — basically whenever you remember them — for the next hour or so.

5. By then the onions will have transformed to a deep, sweet golden brown. Enjoy!

Make caramelized onions any time you find an excuse to do it. There are a lot of excuses. They’re great on baked potatoes. They add depth and goodness to almost any stock, soup or sauce. They are delicious and extremely versatile, a sweet and savory complement to anything except for ice cream. Maybe even that. I’d try it.

After a few bouts of onion-cooking, try something else. Sautée some mushrooms. Fry some eggs (not scrambled — not yet). Pancakes are great. If your pan performs poorly at any point in this process, send it back to Seasoning 101 and 202. Eventually — within days, weeks or months — it will get there.

That’s seasoning in a nutshell: add fat, heat it, scrape-scrape-scrape, rub rub rub, repeat, repeat, repeat. You know your pan has arrived when you flip an egg and it positively slides across the surface.

Next up, how to clean the damn thing.