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I know that with cast iron skillets, one isn't supposed to put them in a dishwasher to allow bits of what was cooked (called seasoning) to build up, since some people think that that produces better tasting food (maybe it does, I'm not taking a stance on this), but what would happen if one dishwashered it? Can it then be used like a stainless steel skillet (meaning spray some olive oil cooking spray to prevent sticking at each use) that isn't so sensitive to overheating and can be put in the oven, or does it cause some sort of problem, like a release of toxins or rust?

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    These are the consequences. – nanoman Mar 28 at 8:51
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    Obligatory xkcd: xkcd.com/1905 – BWFC Mar 29 at 10:34
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    "Can it then be used like a stainless steel skillet that isn't so sensitive to overheating and can be put in the oven," Cast iron skillets CAN be put in the oven – Kevin Mar 29 at 13:43
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A cast iron skillet which is regularly washed in the dishwasher will be progressively stripped down to bare metal, which will quickly and consistently rust. It will not be usable for cooking until you clean it of the rust and re-season it.

Incidentally, I think you might be confused by the term "seasoning". Seasoning consists of polymerized oil, not "bits of food", and its purpose is to protect the skillet and reduce sticking, not to produce better tasting food. If you don't want to use a seasoned pan, for whatever reason, you should not use cast iron.

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    If you want some of the benefits of cast iron without the bother of seasoning, enamelled cast iron might be suitable. Some of the confusion may be that (apart from "seasoning" often meaning adding flavour), seasoning some things is supposed to help make a tasty end result: woks, though that's probably just that a well seasoned wok works well; moka pots etc. – Chris H Mar 27 at 21:49
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    @RLH, to use on the pan, or the housemate? – Mark Mar 29 at 0:14
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    Who chose to call that seasoning anyways? Silly. – DKNguyen Mar 29 at 20:23
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    @DKNguyen would you expect a “seasoned traveler” to be dusted with cumin? The name comes from the idea of the pan being put through its paces, so to speak. – Sneftel Mar 29 at 20:38
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    @DKNguyen People do use "seasoning" in the context of leaving wood out in the open for several years before using the wood to build furniture or houses. Properly seasoned wood is harder, tougher and more resistant to rot. There is a long tradition of "seasoning" to mean to condition something over long use (seasons) which makes more sense than the meaning to salt or spice something since salt has nothing to do with seasons/time – slebetman Mar 29 at 23:09
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First, about the literal question in the title. I would go farther than Sneftel: almost no cast iron skillet is so perfectly seasoned that the metal is perfectly sealed. The seasoning is good enough for protection against air, but dishwasher powder dissolved in warm water is super corrosive to iron. Already in the first wash, you will likely get some rust developing underneath the seasoning.

Second, I am not entirely sure, but it seems that you believe that 1) a dishwasher will strip the seasoning, and 2) either a cast iron pan or a steel pan cannot be used at high temperatures or be put in the oven. Both these ideas are very much wrong. If you want to strip the seasoning, that is done with either lye, mechanical action, or in an oven's self-cleaning cycle. The dishwasher won't do it, unless you wash it frequently enough that enough rust builds up for the seasoning to flake, which is not what people want to get when they strip a seasoning. And you can absolutely put both a cast iron pan and a stainless steel in the oven or heat it to temperatures beyond what is needed for any kind of cooking or baking, without any damage to the seasoning of the cast iron pan.

Third, if you do have a cast iron pan without seasoning (which you seem to hope to achieve through the dishwasher, but you can't, see above), it will not only be stickier than a seasoned pan ("spray some olive oil spray" won't be sufficient, you will need a decent layer of oil), but it will also rust in your cabinet within a few days to weeks. Also, depending on how you use it, it will likely build seasoning on its own just by shallow-frying certain foods in it.

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    I don't think the OP believes 2 -- rather the OP wants the benefits of cast iron (can stand up to high temperatures and be put in the oven) but used like stainless steel (wash in the dishwasher). – user3067860 Mar 28 at 11:13
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    A single pass though a dishwasher (courtesy of a new housemate) was enough to rust one of my cast iron pans (stock Lodge seasoning plus a year of use). – RLH Mar 28 at 16:27
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    @KonradRudolph you missed the first part of that phrase. It's "to be used like a stainless steel skillet that isn't so sensitive..." It's not obvious because there's a big parenthetical phrase in the middle, but they're talking about something less sensitive than stainless steel, not seasoned cast iron. – Kat Mar 28 at 20:31
  • @Kat Yeah I guess so. – Konrad Rudolph Mar 28 at 22:21
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    @Kat indeed, thank you for mentioning that interpretation. I now updated it to cover both possibilities – rumtscho Mar 29 at 16:09
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Based on experience with a carbon steel pan, which, as far as I know, is equivalent to cast iron in these regards:

If you wash it in the dishwasher regularly, and do not season it, you will just have a bare piece of non-stainless steel. This will have no non-sticking properties and will stick badly even if you add plenty of oil/butter for cooking; and it will rust quickly. At this point, you might simply not be using such a pan at all and switch to stainless or teflon.

The rust itself is no health concern. It does enter the food, potentially visible, and potentially with a slightly metallic taste.

The sticking is just... very bad. It would make me not want to use the pan at all. Note that you never leave the pan with "bits of food" sticking to it, that's not what seasoning is about at all. If your pan has stuff stuck to it, the way to clean it is to heat it up, and deglaze it with hot water (soap not required). Scrub with your metal spatula vigorously while the water is boiling, if needed. After getting rid of the water, let it heat up further until all water residues have vaporized. Then add a very thin layer of your oil of choice (canola, sunflower...), and keep heating until that starts smoking (and keep it smoking a bit). Wipe off any oil residues, and hang the pan to cool off.

This procedure cleans up any bits of food, builds up the seasoning a bit, and sterilizes the pan; it takes a very short time and should be a part of the regular cooking regime whenever it starts sticking.

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    Metal spatulas will scratch and chip off the seasoning. And while thermal shock is less of a problem for cast iron than it is for some other materials, it's still not exactly recommended for durability, so be sure to use hot water for deglazing a very hot pan (though small volumes of cold water are ok, just don't put it under a cold tap or submerge it). – Konrad Rudolph Mar 29 at 10:18
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    Oh, and heating the pan for just 1 minute will absolutely not build up seasoning, that's completely insufficient. In fact, it requires heating the oil over its smoke point to do that, which in turn requires thoroughly heating the whole pan for a substantial amount of time on high heat. – Konrad Rudolph Mar 29 at 10:22
  • @KonradRudolph: I mention that the oil needs to be heated to smoking. For me, on an induction cooking plate, that takes what feels like 1 minute but obviously I have not timed it scientifically. I will remove that exact number as it is not relevant. By experience, this routine most definitely creates seasoning. Finally I do use the words "builds up the seasoning a bit" - if the pan were completely new, I would use one of the usual, well known, but more extensive methods. – AnoE Mar 29 at 11:48
  • @KonradRudolph: for deglazing with water, I did mention to use hot water; and I do not suggest to heat it to oil-smoking temperatures for that step. – AnoE Mar 29 at 11:50

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