Seasoning is not a product and it is not a coating applied at the factory. It is oil that has been heated past the point where it breaks down and bonds into a hard, plastic-like layer chemically fused to the iron. The technical word is polymerisation, and it is the same process that makes linseed oil dry hard on wood.
Which is useful to know, because it explains every rule that follows — and it means nothing you do to a cast iron pan is permanent.
The method
- 1
Wash and dry completely
Warm water, dish soap, a stiff brush. Then dry it with a towel and put it on a hob over medium heat for a minute until every trace of moisture has gone. Water trapped under a fresh coat is what causes patchy results.
- 2
Oil every surface
Cooking face, walls, the outside, the handle and the underside. About a teaspoon covers a 10-inch pan. Use a lint-free cloth or a paper towel.
- 3
Wipe it back until it looks dry
Take a clean cloth and remove as much as you can. The pan should look dry, with a faint sheen and no visible wetness. This is the step that separates a hard seasoning from a sticky one.
- 4
Bake upside down at 230C / 450F for an hour
Upside down so nothing pools. Put a baking tray on the shelf beneath. Expect some smoke; open a window.
- 5
Cool in the oven
Turn the oven off and leave the pan inside until it is cool enough to handle. Cast iron does not like rapid temperature changes.
- 6
Repeat two or three times
Each coat is only molecules thick. A new or stripped pan wants three or four; an afternoon covers it.
Which oil?
Any cooking oil will polymerise. The differences between them matter less than the internet suggests, and the practical choice is a neutral oil with a reasonably high smoke point: grapeseed, canola or refined avocado.
Why pans come out sticky
This is the most common failure and it has one cause: too much oil left on before baking. Excess oil cannot fully polymerise, so it part-cures into a soft, tacky film that picks up dust and feels unpleasant.
The fix is straightforward. Put the pan back in the oven at 230C for another hour with no fresh oil, and the extra will finish curing or burn off. If it is still tacky, scrub it back with coarse salt and start the coat again, wiping much harder this time.
Maintaining it afterwards
A cast iron pan in regular use should not need deliberate re-seasoning. Frying is the best seasoning treatment there is — hot fat and metal, which is exactly what an oven bake simulates.
- Wash it after use, dry it on the hob, wipe a trace of oil on while warm.
- Cook fatty things in it early on — bacon, chicken thighs, steak.
- Avoid simmering acidic sauces in a young pan; acid dissolves seasoning.
- Never leave it wet, and never in a dishwasher.
Two myths worth retiring
Soap does not destroy seasoning. The advice dates from when household soap was lye-based and genuinely could saponify a fat layer. Modern dish detergent lifts food residue and leaves polymerised oil alone. Cleaning a pan properly matters more than protecting a coat that soap cannot reach.
Metal utensils do not ruin a pan either. A steel spatula burnishes seasoning smoother in daily use. What damages it is scraping hard at a young, incompletely built coat — so give a new pan a few weeks before you attack it.
The short version
- Wash, dry completely on a hob, then oil every surface.
- Wipe it back until the pan looks dry. This is the whole trick.
- 230C / 450F, upside down, one hour, cool in the oven.
- Three or four coats for a new pan; none at all for a pan in weekly use.
- Grapeseed or canola. Skip flaxseed — it flakes.
- Sticky means too much oil. Re-bake with none.
Day-to-day washing is a separate question with its own myths, and how to clean a cast iron skillet covers it — including what to do about rust.
