How to season and care for a cast iron pan

A cast iron pan is a lump of iron with a thin, hard coat of baked oil on it. Look after that coat and the pan will sear, fry and bake for longer than you will cook. Almost every cast iron problem (rust, sticking, flaking, a dull grey patch) is a problem with the coat, and almost all of them can be fixed at home in an afternoon.

What seasoning actually is

When a thin layer of fat is heated on iron to a high enough temperature, it changes from a liquid into a hard, slick film. Chemists call the process polymerisation: the fat molecules link up into a solid network that bonds to the surface of the metal¹. That film is the seasoning. It protects the iron from water and air, and it gives the pan its easy-release surface.

Seasoning is not one coat but many. Lodge, the American cast iron foundry, puts it simply: the best way to season cast iron is to cook in it, because every time you cook with oil or fat you add another layer¹. The first layers you add yourself may look patchy, depending on your hob and what you cook. That is normal, and the patches knit together with use¹.

Most pans sold today arrive seasoned from the factory, so a new pan needs a wash and a dry, not a ritual².

Wash, dry, oil

The care routine is three words long².

1. Wash. Let the pan cool a little, then wash it by hand with warm soapy water and a brush or sponge. Yes, soap: the maker recommends it². Avoid the dishwasher and avoid soaking, which is how rust starts.
2. Dry. Dry it straight away with a towel, then put it back on a low hob for a minute or two to drive off the last of the water.
3. Oil. While the pan is warm, rub in a few drops of oil with kitchen paper, then wipe it again as if you were trying to remove it all. What remains is enough.

For food that has really stuck, Lodge suggests simmering a little water in the pan for three to five minutes, then using a pan scraper once the pan has cooled². A paste of coarse salt and a little oil, scrubbed with kitchen paper, works too.

If a towel comes away with dark marks after drying, do not worry. The maker says this is normal and safe, particularly on a new pan or after acidic food or very high heat, and it fades as the seasoning builds¹.

Cooking in it so the seasoning grows

Cast iron heats slowly and then holds its heat for a long time. The commonest mistake is using too much heat². Lodge recommends starting at medium-low and working up, preheating the pan for a couple of minutes, using a little oil or butter, and not fiddling with the food once it is in². The same patience that makes food release from stainless steel works here; our guide to stopping food sticking to stainless steel explains why.

Fatty, high-heat cooking is what builds seasoning fastest: shallow-fried potatoes, seared meat, cornbread, roasted vegetables. Acidic food does the opposite. Tomato, wine, vinegar and lemon slowly break seasoning down, so Lodge advises holding off on them until the seasoning is established, and then keeping acidic dishes to cooking times under about 45 minutes¹.

Reseasoning in the oven

Sometimes the coat needs rebuilding: after scrubbing off rust, when a second-hand pan has been stripped, or when the surface has turned dull and grey. The oven method from the maker goes like this¹:

1. Wash the pan in warm soapy water and dry it completely.
2. Rub a very thin layer of cooking oil over the whole pan, inside and out, including the handle and the base. It should not drip or run when you tilt the pan.
3. Heat the oven to 232 to 260 °C (450 to 500 °F). Put a sheet of foil on the lowest shelf to catch drips.
4. Place the pan upside down on the middle shelf, so oil cannot pool in it, and bake for one hour.
5. Turn the oven off and leave the pan inside to cool.

Repeat two or three times for a pan that has gone back to bare metal. The temperature matters: it is well above the point at which cooking oils start to smoke, which for most oils falls somewhere between 110 and 270 °C³. Expect some smoke, open a window, and use an oil with a high smoke point. Lodge's own test kitchen favours vegetable oil, canola (rapeseed) oil or melted shortening¹.

The most common error is too much oil. A thick coat cannot cure fully and stays sticky. If that happens, put the pan back in a hot oven for another hour.

Fixing the usual problems

Flakes of black coming off. Layers of seasoning that never bonded properly can flake. The fix is to scrub the loose layers away with a nylon brush or salt, rinse, dry by hand and rub with oil; if it keeps happening, reseason in the oven¹.

Rust. Orange spots mean water was left on the iron. Scrub the rust away with steel wool or a stiff brush until you reach grey metal, wash, dry thoroughly and reseason as above. A rusty pan is almost never a ruined pan.

A rough surface. Many cast iron pans are cast in sand moulds, which leaves a slightly pebbly texture that helps seasoning grip. It smooths out with years of use¹.

Food sticking. Usually the pan was not preheated, or the heat was too high and burnt the fat. Lower the flame, preheat longer, and add a little more fat.

Iron in your food

Cooking in cast iron does put a little iron into food. A 2021 systematic review of 13 studies found that cooking in iron pots or with iron ingots increased the iron content of the food; four studies saw significant rises in blood haemoglobin, and the others smaller ones⁴. The authors present it as a cheap help against iron deficiency anaemia, while noting that more research is needed⁴. For most people it is a pleasant side effect, not a reason to eat differently; anyone told to limit iron should ask their doctor.

When cast iron is not the right pan

Cast iron is heavy, slow to heat and dislikes long acidic cooking. For tomato sauce that simmers for an afternoon, use stainless steel or enamelled cast iron. For eggs every morning, a nonstick pan at gentle heat is easier. Our comparison of stainless steel, cast iron and nonstick goes through which pan suits which job. For searing, shallow frying, cornbread and anything that wants steady heat, cast iron is hard to beat, and with ten seconds of care after each wash it will be there for the next generation.