Restoring a rusty cast iron pan
I found a heavy cast iron pan at a flea market for almost nothing. It was orange with rust on the inside and had a thick black crust on the outside. Cast iron is very hard to ruin properly, so it seemed worth a try.
Getting the rust off
I soaked the pan in a mix of white vinegar and water, roughly half and half, for about an hour. Vinegar dissolves rust but will also start eating the iron if you leave it too long, so I checked every fifteen minutes. After that, a steel wool pad and some elbow grease took off what was left.
The bare iron starts to rust again almost immediately, so I rinsed it, dried it with a towel, and put it on the hob for a few minutes until all the moisture was gone.
Seasoning
Seasoning is just very thin layers of oil baked onto the metal until they turn into a hard coating. The important word is thin. I rubbed a little vegetable oil all over the pan, then wiped it off as if I had made a mistake and wanted to remove it all. What stays on is enough.
Then into the oven, upside down, at the highest temperature it goes, for an hour, and left to cool inside. I repeated this four times over two evenings. Each layer makes the surface a bit darker and smoother.
Using it
The first few weeks I cooked mostly fatty things in it — fried potatoes, bacon, pancakes — which helps build up the coating. Now eggs slide around like on a non-stick pan. After cooking I rinse it with hot water, dry it on the hob, and wipe a drop of oil over the inside.
The main rule: never leave it wet. Everything else is surprisingly forgiving.