How is heating it up for 2 minutes to dry it off going to cause rust compared to the 20 minutes you spent cooking with liquid in the pan?

Much more oxygen as it dries. You are not supposed to boil water with cast iron, you need oil when cooking which protects it from air.

The point is don't warm it to dry thinking it will rust less since it's wet for less time. Just let it dry in regular air.

I suppose that might be true, but have you actually done the math here?

If it dries say 50 times faster, does iron rust more than 50 times faster at 400F than at 70?

I have no way of knowing either way, but I've got a cast iron pan that belonged to my great grandmother and I remember my grandmother heating it to dry it off. My mom did the same with it, and now I've done the same--no rust.

I didn't do math. I did an experiment.

I took two identical pieces of metal. Dried one in a warm stove the other on a table.

The one on a table had no visible rust. The one in a stove was completely orange.

I don't doubt that warm metal rusts faster, just how much faster.

There's a pretty big difference between drying something in a warm stove vs applying a direct flame to it on the stove top.

It takes just a few minutes to get the skillet hot enough where the water pretty much instantly evaporates. I'd imagine putting it in a warm stove took much longer to completely dry it.

Direct flame would be even worse. It will rust much faster than it will evaporate.

Reaction speed doubles for every 10 degrees F, but evaporation doesn't.

Reaction speed doubles for every 10 degrees F.

That can't possibly be correct, or at least it's only correct over part of the range.

If a pan rusts at a given rate at 70F, it would rust at 2^33 times that at 400F--those numbers just don't work at all.

Also once the pan heats past the boiling point of water, there is a huge decrease in drying time.

If my cast iron can rust from two minutes on the stove, I need to stop cooking wet foods in it. It has yet to be a problem, though.

Of course. But that isn't what I said.

What I said was that if you are heating the iron in order to speed up evaporation to avoid rust, you are being counter productive. You will avoid more rust (if any would be formed in the fist place), by just letting it air dry.

I don't know what you said, then. People are saying we put our cast iron on the burner for a couple minutes to dry it off and you're saying the direct flame will cause it to rust.

In my house, we stove-dry pans constantly, precisely to prevent rust, and we never get any. It's not intentionally an "experiment", but it's enough to make me think there's an issue with your methodology.

You probably would not get rust anyway, so stove drying isn't hurting anything much.

But it's certainly not helping.

The methodology was not complicated: I washed some porous/rough metal under the faucet, dried it with a paper towel, then put one piece in the oven at 170F, one on the table.

170 is below the boiling point of water, it may speed up evaporation but it won't boil off.

300-400 (what you'd get from the stove top) is above the boiling point, so the water rapidly boils off.

These 2 things aren't comparable.

Maybe iron will rust faster when hot, but I don't think heating it to dry it is an issue -- I do that fairly often, and haven't had a problem.

Here's a counter example: There are many tons of metal in hot desert climates that have a small amount of rust on them, but nothing like the kind of rust from a cold wet climate. There may be complications from cooking, but, and this is without giving it much thought, I'd say that water is a much larger factor than heat.

> in hot desert climates

You still need water.