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Cast-Iron Seasoning and Carcinogens

What prevents the oil in the cast-iron seasoning process from becoming carcinogenic -- since temperatures heating the pan typically exceed the smoking points of the high smoking-point oils used for the seasoning process? Is it enough to wipe the excess oil from the pan at the end -- or, when reheated, could the oil 'embedded' into the iron still leach into whatever is being cooked?

(I've diligently sifted through the numerous threads on cast-iron but haven't come up with an answer. It's quite possible of course that no answer's emerged because no one's been so ignorant as to pose the question -- in which case apologies as well as thanks in advance!)

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  1. What temperature would you be planning to use to season this cast iron cookware? Most recommendations I have seen do not call for extremely high heat. The temperatures most often recommended do not exceed 350 degrees, and many sources recommend as low as 220-250 degrees.

    1 Reply
    1. re: angusb

      I always season mine on the stovetop at low heat, but have come across seasoning instructions that call for 500 degrees in the oven -- i.e., over the 400-some-degree smoking point of oils like grapeseed, peanut, rice bran, etc. -- hence this question. Or might such instructions be assuming that the seasoner is using lard?

    2. The simpler version of this question might be: consensus (on many Chowhound cast-iron threads) seems to be that the seasoning process is supposed to smoke -- like crazy, even. But it's also established that when oil smokes it becomes carcinogenic. What am I missing?

      2 Replies
      1. re: sequins

        You may be worrying about this far too much.
        For some reason, people are making a much bigger deal out of seasoning cast iron than they need to.
        No, it doesn't have to smoke.
        No, you don't even need to use any special "process."
        You don't have to do anything beyond cook a bunch of bacon.
        I did that once when I had a new skillet and an oven that didn't work.
        I guess you could also just sauté a lot of veggies if you are a vegetarian - but bacon dripping work waaaayyyyy better than anything to get a skillet in fine shape fast.

        The point of the oil is toslowly fill the pores in the cast iron with oxidized layers of carbon that becomes harder and harder from repeated heating.
        You heat the skillet to the 350 to 400 degree range - about where you'd cook normal food.
        Above that, oil would smoke, break down, and get bitter.
        (That's also where it begins to give off the dreaded free radicals that can potentially increase the risk that might possibly contribute to the chance of your getting cancer if you don't get run over by a bus first.)

        If you heat a skillet above about 500, you won't get a decent layer of seasoning on it.
        In fact, heating it above that might remove any seasoning you have already worked so hard to attain.
        One of the ways to recondition an old skillet that has been ruined, found at auction or a rummage sale, or just gotten gunky, it to put the cast iron through the self-cleaning cycle of an oven.
        Or you can throw it into the embers of a fire.
        The high temperature of the oven or the fireplace will remove all the seasoning and return the cast iron piece to bare metal.
        We did this with all of my family's cast iron after Katrina. It had been submerged in the vile flood waters for weeks. No way of telling what was in that water so we ran everything through the self-cleaning oven and started all over again with the seasoning.
        We ate a lot of BLTs that Autumn.

        1. re: sequins

          First off, let's get real about the carcinogens in oil. The real threat is with consuming foods deep-fried in oil that has been heating all day (like at a fast-food establishment). With that super-size order of fries, you not only get a LOT of fat (which is a both a cancer and heart disease risk-factor) but you get whatever funky carcinogens that have developed.

          The seasoning layer on cast iron is really thin, and for the most part is well bonded to the iron. I just don't see that much getting into your food. My opinion is that the bulk of the health risk comes from the fat that you add to the pan, whatever the pan material.

          A very real carcinogenic threat comes from eating meats that have been smoked, or that have been either grilled or barbecued, particularly if they have charred. Yet I don't see too many folks turning in their grills and smokers.

          Second, there are two schools of thought when it comes to seasoning temps: low and high. If you read the instructions that Lodge provides, you would see that they are recommending oven temps in the 300-350F range. This is not quite hot enough to get the oil to smoke, but it is hot enough to get the oil to polymerize and bond to the iron.

          However, as you have find with a little research, high temps (400-500F) get the process really going. The advantage to the high temp method is that you are less like to get gummy spots where the oil was a little thick. You get a nice hard coating right off the bat. The disadvantage is that the oil is starting to burn at that temperature, and producing lots of smoke (and who knows what else).

          Anything hotter is unproductive, since it burns the oil and the seasoning and leaves you with an unseasoned pan. This is what happes in your oven during the self-clean cycle.

          Personally, I season my stuff on my gas grill and prefer keeping the heat low, but that is just my preference. What little smoke that gets generated stays outside instead of stinking up the house.

        2. Best idea is to just to i follow
          the manufacturer's directions on seasoning.
          It's no more complicated than
          how to boil water. But if it
          worries you,I'd suggest
          using cookware that doesn't require
          seasoning.

          1. The oil isn't carcinogenic, the seasoning is.
            #1: You don't eat the seaoning.
            #2: You'd need to eat a few ounces of seasoning a day for 10 years to double your chances of getting a related cancer.
            #3: There's little to no chemical difference between the seasoning on the pan, and nicely browned foods obtained by broiling, searing, grilling, etc.
            #4: Your body's natural defenses render most small amounts of such materials harmless. The free radicals are counteracted by antioxidants. It's only when you exceed your body's defenses (see ounces a day above) that any carcinogenic effect kicks in.

            In short, it's FUD (Google FUD) spread by cookware companies selling non-cast-iron products.

            If you're that worried about it, don't eat any browned foods. Thanksgiving turkey, toast, grilled steak or hamburgers, grilled fish, etc. Otherwise realize that folks have been eating those things for centuries, and that the seasoning on a pan is made up of the same polymerized and carbonized stuff.

            1. Thanks to all for the well-reasoned assurances. I will stop worrying about it!