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There are many articles and Reddit posts saying to heat the cast iron on low for a long time and then cook in it. Apparently it’s a bad idea to heat the cast iron on high as heat doesn't flow easily through the metal bulk.

So, how long should I heat up the cast iron?

Normally I put a few drops of water in the pan to check the temperature, but clearly that is not a good idea with cast iron.

Peter Mortensen
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Reine Abstraktion
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    Why are the drops of water a bad idea? That is my method too. Am I going to break something? – Willk Dec 23 '22 at 17:54
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    My infrared thermometer I got from Amazon is the best cooking-related $18 I've ever spent. I generally bring a pan to around 370 then add in my oil and start cooking. – Banjoe Dec 23 '22 at 23:55
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    @Willk I’ve heard stories of cast iron cookware cracking because of people pouring cold water into a (nearly) red-hot pan. But a few drops of water should be fine – it would take a lot more for stress cracks to appear. – user149408 Dec 24 '22 at 11:39
  • "until you can hold your hand about 6-inches above the cooking surface and feel the heat radiating upward." https://cooking.stackexchange.com/questions/5815/why-does-my-food-turn-out-poorly-using-an-all-clad-stainless-steel-fry-pan "Heat the empty pan, **once heated, add a drop of water. If the water stays in a single drop and glides across the pan, you're probably ready to add the oil. If the water splits into smaller drops, it's not hot enough.** This is caused by the water that first touches the pan immediately vaporizing, the rest of the drop floats on the steam." – Mazura Dec 26 '22 at 00:33

2 Answers2

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You heat it until it has reached the heat you need for the recipe you are going to make. It doesn't matter how long.

You can use any method you like to decide when it's ready. You mention that you are comfortable with a water drop method; that's great. You can use it on your cast iron pan, there is nothing to speak against it, and it will work.

Also,

Apparently its a bad idea to heat the cast iron on high

This is nonsense. Of all pan materials that exist, cast iron is the one that is most forgiving to overheating. It also takes longer to preheat than others, so using a high setting for preheating is really practical.

rumtscho
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I think it's more accurate to say "using high heat to preheat a cast iron pan is not always as useful as it would be with other kinds of pans".

Imagine that your pan is bigger than the burner. In that case, a heavy-weight aluminum pan will diffuse the heat sideways, and the whole pan will heat evenly. But with the cast iron pan, it will take a while for the heat to reach the edges. If you use higher heat with cast iron, you'll still have to wait for the heat to equalize across the surface of the pan.

But the high heat won't hurt the pan at all (unless it's so very hot that you burn off the seasoning). And the water-drop method is a fine way to test.

AndyB
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