On Seasoning Cast Iron Pans

Reader Rikki writes:

I know this probably isn’t your area, but I’m trying to season a cast iron pan. The pan maker says I should use low heat to season it, but just about every other seasoning article I’ve seen on the web says very high heat is the thing. Can you tell me: what’s the difference and which method should I use?

Rikki, just because I’m a baking blogger doesn’t mean I can’t flap my fingers for a while on this general cooking subject. It’s pretty interesting stuff! As you surely know by now from your readings, seasoning is the process by which porous die-cast metal pans are transformed into smooth, virtually non-stick cooking implements. In the old days people didn’t think much about seasoning since it just happened over time with use. Today home cooks take a more clinical attitude toward seasoning. As you mentioned, pan manufacturers usually provide instructions on how to season a new pan. The typical procedure calls for a fat of some kind (usually solid) to be applied to the pan in a thin layer, then the pan is baked in a low (300 degree) oven for about an hour. Done correctly, the process yields a slick surface which, if the pan isn’t scrubbed out with soap, works very nicely.

But how exactly does seasoning work? It all has to do with the breakdown of fat molecules. Some of you may recall from previous posts on fats that fat molecules are “E”-shaped: three long fatty acid molecules attached to a “backbone” of glycerol. Heat them though, and they begin to break into pieces. The individual fatty acids come loose from the backbone, at which point they’re free to bond with whatever type of molecule catches their fancy. If they happen to be near iron, they’ll bond to that, with their polar end down and their “fatty” end up. The end result for the pan is that all the tiny pores in the metal get plugged up and the surface becomes slick.

Many cast iron aficionados kick the whole seasoning procedure up a proverbial notch by employing a liquid fat (oil) and high heat. This method not only breaks the fatty acids off their glycerol backbones, it breaks the fatty acids themselves into pieces — pieces which, in the presence of metal and oxygen, rearrange themselves into chains known as polymers. These polymers inter-weave with one another to create an incredibly hard and dense plastic-like film. If you’ve ever spent hours trying scour blackened drips of burnt fat off the exterior of a sauté pan, you’re familiar with the stuff. You find it on the outside of pans and on cooktop surfaces because that’s where the big heat is.

To create a polymer film on the inside of a pan you need oil (because less saturated fats make harder polymers) and an oven temperature of 500 degrees or more. It’s a stinky, smoky process and one that in my opinion isn’t strictly necessary. To my mind the best way to season a cast iron pan is to employ the low-heat method, then use it as often as you can being mindful of soap at cleaning time. But that’s just me. For more on high-heat seasoning, see this very interesting post here.

15 thoughts on “On Seasoning Cast Iron Pans”

  1. There is a lot of mystique surrounding cast iron seasoning it seems. Many of the blogs defy tradition and advocate high heat and a variety of oils. I find the traditional way works as good as any of the new-age alternatives. But whatever works. Most important thing is to not expect a perfectly even-colored seasoning initially. It takes time. Suggestion for making seasoning faster: use the pan a lot. Especially for bacon and burgers intially. Lots of bacon and burgers!

    1. Bacon…burgers…now that’s what I call seasoning. Well said, Mr. Shaw!

      – Joe

  2. My cast-iron pans are almost thirty years old and they have hard, thick seasoning; result of years of sauteeing and frying. I wash them with soap; I will even let them soak a little. I only baby them by drying them off immediately, rather than letting them sit out damp.

    I think all the fuss about “you can’t wash them with soap” and “you can’t use them for acidic food” is nonsense.

    1. Hey Karen!

      Well said. I’ll differ only in that I think you need to be careful with soap when you’re getting the seasoning going at first. It can be delicate. But after years of use you’re right: that layer is thick and nigh impenetrable. I use light soap on mine as well, and even scrub them some if there’s anything really cooked on (though I confess I use lemon halves and coarse salt as an abrasive…does that count as baby-ing?). 😉

      – Joe

  3. Note that these days, most cast iron pans come pre-seasoned from the factory, and don’t need too much special attention out of the box. Regular use and avoiding harsh cleansers for a time will add to the coating. After a while, you can safely clean seasoned pans with soap and a sponge, though scrubbing with a real abrasive can remove the coating.

    1. Great comment, Chris. My own experience jibes with this, and I never really had to season mine since they can from grandma. God knows how many batches of hash were fried up in those things.

      Thanks very much,

      – Joe

    1. Hey Roger!

      I expect it would, though I’m not really a seasoning expert. I recommend a google search and see what comes up!

      – Joe

      1. Coconut oil may not be a good choice, though I don’t have personal experience with it. I caught this in the comments section of the article you linked in the opening post. A poster named Josh provided a little more info on fat polymerization:

        “A more direct measurement of an oil’s ability to polymerize is its iodine value. In a nutshell, this measures how much iodine an oil can absorb, which in turn is an indication of how many bonding sites are available for polymerization.”

        Apparently, higher iodine value numbers indicate a more efficient potential polymerization. News to me.

        Josh linked to a table that lists coconut oil at a very low iodine value (the lowest listed). If his info is correct, it raises questions about whether coconut oil would be a good choice for cast iron seasoning.

        Here’s a direct link to Josh’s comment:


  4. Having been around a seasoned block a few times and having a set of my grandmothers nearing 100 year old cast iron pans(!) (and working in restaurants didnt hurt anything) the best trick i learned was to drop an old cast iron pan or pot into the fryer. Most restaurants dont mind, ive even taken mine to a local restaurant and asked them, ever so kindly, whilst imbibing, to do me a solid (or liquid fat in this instance.) most of the time they will oblige and let it sit for 10 minutes or so. I dont ever worry about the handles in this case since i havent ever cooked anything on a cast iron handle that i can remember. Just a tip take it or leave it but it works fantastic.

    Suppliment: i do have a home fryer that holds a good temp and ive done it home with great succ,ess as well.

    1. Hey Dave!

      Fascinating — and entertaining — technique! I’d file that in the “do not try this at home” file, but if you can get a buddy at a restaurant to do it for you, why not?

      Thanks for the tip, home boy!

      – Joe

  5. On a recent lazy fall afternoon while burning off some leaves and twigs from the lawn I got the idea to throw dinner in a cast iron pan and put it over/in the fire to roast.
    When dinner was done I pulled the pan from fire and saw that heavy lumpy seasoning on the outside of the pan had burned away, as well as the perfect finish on the inside. Sigh. I had to start from scratch to re-season the decades old pan. While it did not occur to me that the fire would burn away any of the finish on the pan, I was happy to have the layers of hardened lumpy polymers which had accumulated on the outside of the pan be gone.

    I learned something that day, how to restore a pan to an unseasoned state while also cooking up dinner. I have contemplated repeating the process with a few other pans that have accumulated a bit to much on the outside of the pan, I just need more leaves and twigs, and a bit less snow.

    Go Cast Iron Cookware!

  6. i have been thinking of cast iron pans just because the so called “non stick” ones do stick and i shudder to think of where the “non stick” is going!!
    But i hadnt realised you had to baby the pans? I may take a more almost Laissez-faire attitude (food based not ecomomics) and just cook with the thing and let time make it work

    after all.. treat right.. the pans will no doubt out last me 🙂

    1. Hey Fi!

      I think laissez-faire is a great idea. The way the “non-stick” effect cam into existence, or so I understand, was that folks in places like Appalachia didn’t wash them often — just one more trip down to the crick in the valley to fetch another bucket of water! Turns out it really makes sense. Just wipe them out and that’ll generally do! Best of luck!

      – Joe

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