Seasoning (the pan)

The bonded polymerised oil layer that makes iron cook without sticking and protects it from rust. It is applied in very thin layers, heated past the smoke point, and then used.

After any high-heat run, wipe 1/2 tsp of high-smoke-point oil over the whole interior while the pan is warm, including the walls, then store it dry.

Seasoning is not a coating that can be scrubbed off by washing up. Hot water and a soft sponge do not remove it; abrasive pads, steel wool and long acidic simmers do.