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How to Clean a Cast Iron Skillet (Soap Is Fine)

The routine takes two minutes. The rust rescue takes an afternoon, and it always works.

By The CalcBold Kitchen Desk7 min readUpdated 987 words
Title card reading How to Clean Cast Iron with the subtitle soap is fine, water is not the enemy
Two rules do all the work: never let it sit wet, and never let it sit in the dishwasher.

Cast iron has a reputation for being demanding that it does not really deserve. There are exactly two rules, and everything else people tell you is either a consequence of them or a myth that outlived its cause.

Do not let it sit wet. Do not put it in the dishwasher. That is the whole of it.

The daily routine

Clean the pan while it is still warm — residue lifts far more easily then. Hot water, a stiff brush or a chainmail scrubber, and dish soap if you want it. Then dry it properly, which means a towel followed by a minute on the hob until no steam rises. Finish with a few drops of oil rubbed over the cooking face and buffed until the pan looks dry.

Five-step diagram of the daily cast iron cleaning routine
Drying on the hob is the step that prevents rust. A towel alone leaves water in the pores.

Stuck-on food

The instinct is to fill the pan with water and leave it. That instinct is precisely what rusts pans, and it is unnecessary — a hot pan releases stuck food faster than a cold soak does.

  • Simmer water in it. Half an inch, bring it to a boil, scrape with a wooden spoon. Everything lifts within a minute.
  • Coarse salt. A tablespoon and a folded paper towel makes an excellent non-damaging abrasive.
  • A metal pan scraper. A few pounds, and better at this than anything else.
  • Chainmail. Ideal for burnt-on residue; it removes carbon without cutting into seasoning.
Comparison of safe and harmful cast iron cleaning practices
Almost everything on the right hand side involves water sitting somewhere for a while.

Rust is not the end

A rusted cast iron pan looks ruined and essentially never is. Rust is surface oxidation on iron that is at least several millimetres thick, so scouring it off costs you nothing structural.

Four-step process for removing rust from a cast iron pan and re-seasoning it
There is no such thing as a cast iron pan too rusty to save. Only ones not worth the afternoon.

Scour back to bare grey metal with steel wool, or soak in a 50:50 vinegar and water solution for no more than an hour — vinegar keeps eating iron once the rust is gone. Wash, dry hard (bare iron flash-rusts within minutes), then season three or four times.

The full seasoning method is in how to season a cast iron skillet.

Reading the symptoms

Table matching each cast iron problem to its cause and fix
Black residue on a paper towel is carbon, not seasoning coming off. It is harmless.

One symptom worth calling out: black residue on a paper towel after wiping. Almost everyone assumes this is seasoning coming off. It is loose carbon from cooking, it is harmless, and it stops after a few wipes. Seasoning does not transfer to a cloth — that is the definition of a cured coat.

Storage

Store it bone dry with a trace of oil on it, and put a paper towel inside if pans are stacked or if the pan lives somewhere humid. If it has a lid, store the lid off or ajar so moisture cannot be trapped against the cooking surface.

Checklist of stuck-food techniques, storage advice and things never to do
Store it with a paper towel inside. It costs nothing and absorbs the humidity that starts rust.

The short version

  • Clean it warm, with hot water and a brush. Soap is fine.
  • Never soak, never dishwash, never air dry.
  • Dry on the hob until no steam rises, every single time.
  • Wipe on a trace of oil while it is still warm.
  • Stuck food: simmer water and scrape, or use salt.
  • Rust is recoverable. Scour, dry, re-season.

Common questions

Can you use soap on a cast iron skillet?
Yes. Modern dish detergent removes food residue without affecting polymerised seasoning, which is chemically bonded to the iron rather than sitting on it as grease. The rule against soap comes from the era of lye-based household soap and no longer applies.
How do you remove rust from cast iron?
Scour it back to bare grey metal with steel wool, or soak in a 50:50 vinegar and water solution for no more than an hour — vinegar keeps attacking the iron once the rust is gone. Then wash, dry thoroughly on a hob, and re-season three or four times.
Why is food sticking to my cast iron pan?
Usually thin seasoning or an under-heated pan. Preheat for two to three minutes over medium before adding fat, and cook a few fatty things — bacon, chicken thighs — to build the coat. Eggs are the hardest test and should be attempted once the pan is established.
Can you soak a cast iron pan?
No. Soaking is the most reliable way to rust cast iron, because standing water reaches the bare metal through any thin spot in the seasoning. For stuck-on food, simmer half an inch of water in the pan and scrape instead — it works faster anyway.
What is the black residue coming off my cast iron pan?
Loose carbon from cooking, not seasoning. Cured seasoning is bonded to the iron and does not transfer to a cloth. The black wiping is harmless and stops after a few passes; if it never stops, the last seasoning coat did not fully cure.
Should you oil cast iron after every wash?
A very thin film while the pan is still warm is good practice, particularly in a humid kitchen. Use a few drops and buff until the pan looks dry — leaving visible oil on a stored pan turns sticky and can go rancid.

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