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I just cleaned up a rusty cast-iron skillet and I would like to season it. The thing is that I don't have lard handy and I'm wondering whether any of my other oils and fats would do.

I have: canola, olive, sesame and almond oil.

Also, I've heard that appying the oil and reheating multiple times improves the seasoning. Is it true? How many times does it make sense to repeat the process?

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The best is flax oil. The next best is soybean oil. The third best is liquid canola (not hydrogenated Crisco).

This is because of where those oils are listed on iodine index; which is a measure of how much an oil will polymerize. Polymerization is when oil turns into plastic and is the actual chemical process responsible for "seasoning".

Here's a whole site dedicated to this topic with more detail:
Chemistry of Cast Iron Seasoning: A Science-Based How-To

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  • -1 because I would argue explicitly against high iodine - see the answer I posted.
    – rumtscho ♦
    Dec 10, 2018 at 16:02
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This question has been answered several times as part of more general questions about seasoning. See the (closely) related links in the related questions list. This one in particular: What's the best way to season a cast iron skillet?

Specifically about oil- you want to use an oil that has a high iodine value: http://www.journeytoforever.org/biodiesel_yield.html#highiodine

Of those you listed canola (rapeseed) would be highest. If you can find soybean oil it would be even better.

These oils polymerize more easily. To create an even coating with good adhesion, multiple thin coats work well. I have read of people doing as many as 6 coats but, in my opinion, you should do at least 2 or 3.

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    Wait, is there anywhere you can't find soyboil oil? Check ingredients on the bottle labeled "vegetable oil", it's probably either soybean or a mix of soybean and canola. Also refined flax seed would be better (but that actually is much harder to find)
    – derobert
    Mar 29, 2011 at 18:23
  • In your reference about iodine values, it says that sesame oil is 104-120, and rapeseed is 94-120. So sesame is actually better.
    – Simon David Pratt
    Jul 29, 2016 at 17:18
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I will disagree with the top answers here and say that it is best to look for something saturated, with low iodine value. I personally stand by lard, but there are other options.

The advice that suggests high iodine oils is based on their easy polymerisation. So, if you don't execute your process perfectly, you end up with a polymer layer for a high iodine oil, and a greasy pan for a low iodine oil. Sounds like high iodine wins, right?

Well, this superficial advantage is actually their biggest disadvantage. The polymer you get from a badly executed seasoning with a high iodine oil is a major PITA. Enough of the abundant "sticky sites" on the molecules of the oil have made a connection to form the polymer - but even more are still free, available to grab on to something else, for example the food you are frying. The coating is soft, gummy, and sticky, and I have had it come off in patches during use. It can be hardened under the right circumstances, but that's not easier than getting a low iodine oil to harden (and I suspect it might be even trickier).

Save yourself the grief and go for the low iodine oils. I would say that whatever makes a nice firm bar of soap - lard, palm oil, coconut - is a good choice here. If you can get it right, it's a great layer - and if you can't, you at least know that you're back to the drawing board, instead of a silent failure that will cost you nerves down the road.

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  • Update: I cannot vouch that the iodine number is the cause for the nice polymerization properties, although it sounds intuitively logical that oils which make harder, nonsticky soap might make harder, nonsticky pan surfaces. I can however tell you that, from personal experience, there is a very high correlation between the {low iodine, high saturation} combination of the oil and the final quality of the polymer layer. And for my kitchen, that's quite sufficient.
    – rumtscho ♦
    Dec 23, 2019 at 13:32
  • Could you explain what your answer is based on, please? Thanks.
    – Jonas Stein
    Apr 12, 2021 at 22:29
  • @JonasStein On personal experience. I have used flaxseed oil for many applications, including soapmaking, wood finishing, caring for garden tools, etc. And with time, I came to recognize the gunkiness and stickiness that is always present in its polymers, it is the same one I was seeing in my pans seasoned with flaxseed oil. When I used other fats, the hardness and smoothness of the seasoning roughly corresponded with the hardness and smoothness of soaps made with the same fat, and I assumed that this is due to the iodine number, since that is well-known in the soap making literature to...
    – rumtscho ♦
    Apr 14, 2021 at 19:29
  • ... create that difference in hardness. Also, it makes theoretical sense, since the iodine number is a proxy measure for how many "holes" there are to fill in the polymer on the molecular level. I admit that my explanation for the reasons may be wrong, but I still can confirm my empirical observation that flaxseed oil makes a gummy seasoning layer that is sticky and peels off easily, while saturated fats make a hard, shiny, durable layer.
    – rumtscho ♦
    Apr 14, 2021 at 19:33
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From personal experience, I have seasoned my Lodge cast iron skillet recently following the process described here and I achieved good results with basic Crisco, which is more or less Canola oil. So far so good: no sticking and great tasting results. I went through the process five times, but I think that may have been a little overboard. Perhaps someone with more practical experience can comment, but I didn't see a huge difference between the fourth and fifth seasoning. After the third round the pan was already a rich, black color with the sheen of a well seasoned cast iron utensil. However, if you are starting from a freshly scoured pan--you mentioned that you are cleaning up an old rusty pan--it may make sense to go through the process a couple of extra times to make sure all the nooks and crannies are properly filled. Mine came from the factory seasoned, but it wasn't done very well--I had food sticking after about a month. Since I re-seasoned myself it's been going strong for a couple of months now.

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  • I'm sorry, but there is no Crisco around here (I'm in Japan). I've got the oils that I mentioned right now. If none of them works, I'll go and buy some lard, but I'm trying to save me a trip to the store :-)
    – ddimitrov
    Mar 29, 2011 at 13:58
  • You could use Canola, as that's more or less what Crisco is. I'm sure someone with more expertise can give you the comparisons between oils. I just wanted to share my experience :).
    – Jduv
    Mar 29, 2011 at 14:05
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Having grown up in the southern US, the traditional seasoning of cast iron in those parts was to simply cook bacon in it a few times. Nothing near as fancy and involved as what you see recommended these days. That has been my usual lazy approach.

On a recommendation from a cast-iron retailer, I have started using the new fancy approach (rub with oil, bake to polymerize) using flax-seed oil. I have to say that the flax-seed oil gives a very strong coating. Nearly impossible to remove from the sheet pan I used to catch the drips during the oven 'cure'.

If I have a complex-shaped cast-iron item (grill, back-side of skillet) I use the flax-seed approach. If I want to simply build up the coating on the inside of a skillet, I cook the bacon. Always a good excuse to cook up a batch of bacon.

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  • The reason bacon works so well is the salt, which has iodine in it :-)
    – Escoce
    Dec 10, 2015 at 23:05
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    Only if the salt is iodized. I'm not sure that would necessarily be the norm for curing bacon.
    – PoloHoleSet
    Oct 4, 2016 at 15:24
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    The iodine value of a fat is a metric for saturation but not an indicator of any amount of iodine present in the fat. It's called the "iodine value" in reference to the fact that you can test how saturated a fat is by iodometric titration. I am suspicious about the relevance and veracity of @Escoce's comment.
    – Air
    Jan 2, 2019 at 20:48
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For seasoning cast iron cookware use Mineral Oil (food grade)

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    Mineral oil is a petroleum byproduct. It can be food grade, but keep that in mind when using it to season something you cook on. Personally I would stick with a vegetable oil.
    – lemontwist
    Nov 3, 2012 at 10:30

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