How to Season a Cast Iron Pan
Quick steps (2 h)
You need: Cast iron pan, Lint-free cloths or paper towels, Neutral high-smoke-point oil or shortening, Oven, Baking sheet or foil
To season a cast iron pan, coat it in a very thin layer of oil and heat it past the oil's smoke point so the oil bonds into a hard, slick, plastic-like layer. One hour in a 230 to 250 °C / 450 to 480 °F oven per coat, repeated 3 to 6 times, builds a durable, naturally nonstick, rust-resistant finish.
What seasoning actually is
Seasoning is not oil soaked into the pan. It's oil that has been chemically transformed into a solid coating.
Vegetable oils are made mostly of unsaturated fats, which have reactive double bonds in their carbon chains. When a thin film is heated hot enough, past its smoke point, oxygen attacks those bonds and the molecules link to one another in long, cross-connected chains. This is polymerization. The liquid oil becomes a hard, dry polymer, a little like the finish on a varnished table. Some of it also carbonizes, which is why seasoning darkens to black.
That polymer bonds to the iron's rough, porous surface and fills its tiny pits. It protects the metal from water and air (so no rust) and gives food a smooth surface to release from. See seasoning cast iron for more of the chemistry.
Why thin coats matter most
Polymerization needs oxygen, and oxygen reaches only the surface of the oil. A thick layer cures on top while the oil underneath stays liquid, leaving a gummy, sticky film that can bubble and flake. A film so thin the pan looks nearly dry cures all the way through in an hour.
Many thin layers are always better than one thick one. Each layer bonds to the one beneath it, building a smooth, glassy finish.
Choosing an oil
| Oil or fat | Notes |
|---|---|
| Canola or vegetable oil | Cheap, reliable, good all-rounder |
| Vegetable shortening | Easy to apply thinly; traditional choice |
| Grapeseed or sunflower | High in unsaturated fat, polymerizes well |
| Flaxseed | Very hard finish, but brittle and prone to flaking |
| Butter, olive oil | Not ideal for base coats; milk solids or lower smoke point leave a softer, uneven layer |
Bake at a temperature at or a little above your oil's smoke point. If your oven tops out lower, bake longer.
Steps
- Wash the pan with warm, soapy water and scrub off any rust or flaking seasoning.
- Dry it completely, then warm it on the stove for a few minutes to drive off hidden moisture.
- Heat the oven to 230 to 250 °C / 450 to 480 °F, with foil or a baking sheet on the lower rack.
- Rub about 1/2 teaspoon of oil over every surface, inside and out, including the handle.
- Wipe off the oil with a clean cloth until the pan looks almost dry.
- Place the pan upside down on the upper rack and bake for 1 hour.
- Turn off the oven and let the pan cool inside.
- Repeat the oil, wipe and bake cycle 3 to 6 times for a durable base layer.
Baking upside down lets any extra oil drip off instead of pooling. Expect some smoke; turn on the range hood and open a window.
Chef Fizz says: Wipe it like you made a mistake and you're trying to remove all the oil. You won't. There's always enough left behind.
Maintaining seasoning day to day
The best way to keep seasoning strong is to cook with the pan often, especially fatty foods like bacon, fried potatoes and seared meat. Each session adds a bit more polymer.
After cooking:
- Clean it while still warm. Use hot water, a brush or scraper, and a little soap if needed.
- For stuck-on bits, scrub with coarse salt and a splash of oil, or simmer a little water in the pan for a minute and scrape.
- Dry it immediately with a towel, then set it over medium heat for 1 to 2 minutes to evaporate the last moisture.
- While it's warm, rub in a few drops of oil and wipe it thin.
Store it in a dry place. If you stack pans, put a paper towel between them to absorb humidity and protect the surface.
Re-seasoning and rust repair
Patchy or dull spots. Clean the pan, oil it thinly and do one oven cycle.
Light rust. Scrub it off with steel wool and soapy water, rinse, dry on the stove, then re-season with 2 or 3 coats.
Heavy rust or a thrifted pan. Soak it in equal parts white vinegar and water for 30 minutes to an hour, checking often. Acid eats the rust, but it will eventually attack the iron too. Scrub, rinse, dry immediately, then build up 4 to 6 fresh coats.
Stripping to bare metal. A self-cleaning oven cycle can burn off old seasoning, but the extreme heat can warp or crack older pans. Oven cleaner (lye) in a sealed bag for a day or two is gentler on the metal. Wear gloves and rinse thoroughly.
Common mistakes and fixes
Sticky or tacky surface. Too much oil or too low a temperature. Bake again for an hour, hotter if possible, then use thinner coats.
Flaking black bits. Usually thick or brittle layers (flaxseed is a common culprit) lifting off. Scrub away the loose patches and re-season with thin coats.
Food sticks even when seasoned. Often the pan wasn't hot enough or the food went in wet. Preheat the pan for 5 minutes on medium, add fat, and pat food dry before it goes in.
Rust after washing. The pan wasn't dried completely. Always finish with a few minutes over heat.
Metallic taste. Acidic foods simmered too long. Re-season and save long tomato or wine braises for enamelled pans.
Avoiding metal utensils. Not necessary. Well-cured seasoning stands up to a metal spatula; it may even smooth the surface over time.
Questions
What is the best oil for seasoning cast iron?
Any neutral oil that's fairly high in unsaturated fat works: canola, vegetable, sunflower, grapeseed or vegetable shortening. Flaxseed makes a very hard coat but can flake; technique, thin coats and enough heat matter more than the oil.
Can you use soap on cast iron?
Yes. Modern dish soap doesn't contain lye and won't strip polymerized seasoning. Just avoid long soaks and dry the pan thoroughly right away.
Why is my cast iron sticky after seasoning?
Too much oil, or not enough heat or time. The excess didn't fully polymerize. Bake it again at 230 to 250 °C / 450 to 480 °F for an hour, and use much thinner coats next time.
How do I remove rust from a cast iron pan?
Scrub the rust off with steel wool and a little soapy water until you see bare grey metal, rinse, dry on the stove, then re-season. For heavy rust, soak in equal parts white vinegar and water for no more than an hour first.
Can you cook tomatoes in cast iron?
Briefly, in a well-seasoned pan, yes. Long simmers of acidic foods like tomato sauce or wine braises can wear thin seasoning and give a metallic taste, so use enamelled or stainless pans for those.