HOME > Chowhound > Cookware >

Discussion

seasoning cast iron: contradictory methods, and which is best?

i love cooking in and maintaining my housemates' cast irons. so when i moved to my new apartment, i bought a new lodge pan and a bunch of old nasty rusty mysterious-goo-covered ones off of craigslist that someone had been using as country kitsch wall decoration. i want to clean and season them properly, but the methods i've found online contradict each other wildly -- some say to clean the crud off with soap, others forbid any soap even for the initial cleaning. some recommend steel wool, others frown on it. vinegar soaks? baking the rust and goo off? what to do? some seasoning methods require a lot of oil at very high heat, others a tiny bit at 200 degrees. the times vary too.

so, do all of these particulars of temperature, heating time, and cleaning method actually affect the pan, or would basically any combination of scrubbing, oil, and heat do the trick? what do you all swear by?

thanks, you guys!

  1. Click to Upload a photo (10 MB limit)
Delete
  1. Most of the folks I've seen season cast iron overheat the pans and that's not a good thing.
    If I procure a pan, grill, etc. that has been abused I first make certain that all of the rust, corrosion etc. is thoroughly cleaned off. Whatever it takes to clean the iron (steel wood, sand paper, even sand blasting or bead blasting of the pan is worth the expense) is what I use. NEVER use chemical cleaners.
    Of all the resources on care and use of cast iron I've read, this site is (IMO) the best single source for the type of information you're looking for. It focuses primarily on dutch ovens but all the principals that apply to cast iron dutch ovens apply equally to the care and feeding of any cast iron cookware.

    http://papadutch.home.comcast.net/~pa...

    2 Replies
    1. re: todao

      thanks, todao! that site looks good.

      1. re: todao

        I have a custom built cast iron wood stove that I used to put oil on to blacken and shine up. It's been 3 years since any oil has been applied. I've recently been told the oil prevents spraying high heat paint on because of the past use of oil. Is this true or can I simply steel wool the rust off and apply the spray paint. For as briefly the oil lasted, I find it difficult to believe I cannot finish the stove to beauty.

      2. On America's Test Kitchen, Chris Kimball cleaned a rusty cast iron pan with table salt and enough water to form a paste, using a wad of aluminum foil to scour it with, and plenty of elbow grease. I've successfully done the same. You then rinse in hot water, dry well, and rub with oil. Do the oil after every use until the food releases easily.

        8 Replies
        1. re: greygarious

          Are you sure he used water and salt? I thought it was oil and kosher salt and then paper towels to scrub while it was heating on a burner. Anyway, that's how I did it. I bought a Lodge 12" cast iron skillet with the helper handle for $6 at a flea market. It was quite rusty so I used the side burner on the gas grill (just in case it got messy, I wanted to do this outdoors) put some oil and salt in the pan and used a steel wool pad and then a bunch of paper towels to scrub it. I used quite a few paper towels. I just tossed them in the grass and kept scrubbing until the rust was gone and it was all oiled up. Then I left it on the burner to get quite hot and a little more oil. The best thing for the pan now is to use it a lot.

          1. re: John E.

            Rust reacts with aluminum in the presence of a reactive chemical like chlorine in salt. The aluminum pulls the oxygen molecules from the rust, leaving iron powder and aluminum oxide.
            Check out the thermite reaction: http://en.wikipedia.org/wiki/Thermite

            Personally, I prefer a drill and a sanding disk, as it makes the surface smoother, plus I'm a lazy son of a gun, but that's just me.

            1. re: ThreeGigs

              I seem to be missing something. Where does the aluminum come from? Cast iron rusts, aluminum doesn't rust (although it has other chemical reactions to boiling water and acids).

              1. re: John E.

                I think the aluminum part come from greygarious's suggestion of using a piece of aluminum foil.

                1. re: Chemicalkinetics

                  I must have stopped reading after he said water. I don't remember Kimball using aluminum foil. I thought it was a wad of paper towel scrubbing with salt and oil.

                  1. re: John E.

                    JohnE,

                    I use your method for cleaning. Oil with salt with paper towel. I don't know what Kimball uses. There are many workable methods. People have used cast iron for thousands of years in many parts of the world. I am sure there are hundreds of functional methods of taking care of cast iron cookware.

                    1. re: John E.

                      Doesn't the paper towel shred really quickly?

                      1. re: EWSflash

                        I had steel wool under the paper towel doing the scrubbing work. The paper towel was mostly there to protect my fingers from the hot oil.

          2. ramonasaur: "so, do all of these particulars of temperature, heating time, and cleaning method actually affect the pan, or would basically any combination of scrubbing, oil, and heat do the trick? what do you all swear by?"

            Everything that you need to know, in detail:

            http://chowhound.chow.com/topics/4768...

            As extended and emended:

            http://chowhound.chow.com/topics/6699...

            Accept nothing that contradicts the advice in those two links.

            2 Replies
            1. re: Politeness

              Wow, seems I have a cast-iron legacy :-) Thanks!

              1. re: ThreeGigs

                ThreeGigs: "Wow, seems I have a cast-iron legacy"

                That's because -- as Carly Simon crooned:
                http://www.songfacts.com/detail.php?i...

            2. "some say to clean the crud off with soap, others forbid any soap even for the initial cleaning"

              If your pan is perfectly fine, then you don't need detergent to clean it because you want to perserve as much seasoning surface as you can. However, if it full of rust and crud, then clean them off with whatever is necessary. At that point, if you have to scarp off some seasoning along with the curd, then so be it. It is about prioritization.

              I agree with most of methods mentioned here. There simply isn't a single workable method. To remove rust, I would try to first use water and detergent to clean, wipe dry, then start to use paper towel, oil and salt to do the real rust removal. The salt acts as an abrasive, the oil acts both as an lubriant and prevent future rusting, paper towel is just easy for throwing it away. I make sure oil is the last thing the cast iron cookware see and not water. If you finish cleaning the cookware with water, then it will likely form a thin layer of rust no matter how careful you are.

              1. It's just 3 steps. 1: Get the pan down to the bare metal. 2: put on a light coat of oil. 3: bake for an hour at 400 degrees or so.

                Ok, details, details, details.
                1: Bare metal. How you get it to bare metal doesn't matter. Scrape it, sand it, sandblast it, put it through a cleaning cycle in the oven, acetylene torch, on the coals of a charcoal BBQ, chemical strippers... BARE METAL IS BARE METAL. That said, there are a few hints and tips. If you strip the old seasoning with super-high heat or chemicals, be sure to also scrub the heck out of it afterwards. Why? Because any impurities in the old seasoning will still be on the surface of the iron and they have to come off to make sure there won't be anything between the iron and the new seasoning layer. Also, high heat can promote oxides of some alloys used in cast iron, and you don't want them there either. Personally, I recommend a drill and a sandpaper disk, as mechanical methods also smooth out rough areas. After getting it down to bare metal, clean it by washing in soap and water, RINSE WELL to be sure no soap remains and then dry it with a paper towel, and dry it again by heating it a bit on the stovetop or in the oven for a few minutes. Why? Because most water in the US (and elsewhere) is hard water, and if the water is allowed to evaporate instead of being removed, it'll leave behind minerals on the surface of your iron, and you don't want that. Also, heating it a bit makes sure that any water in the nooks and crannies (not pores, cast iron is NOT POROUS) is gone, and the residual heat allows the fat/oil/grease you will apply to thin out a bit.

                2: put on a light coat of oil. Now when I say light coat, most people just don't get it. Touch your nose to a nearby window. Look closely at the mark that's left. That's skin oil, and that's how thick (thin) the initial seasoning coating should be. Almost any kind of oil or grease will do (technically oils are fats, we just call any fats that are liquid at room temp oil... I'll be referring to whatever you use as fat in the rest of my explanation). Crisco, vegetable oil, lard... all good. NOTE: Whatever you use should be pure fat (oil). Lard is OK if it's processed, but for the initial seasoning don't use impure oils like baconfat or butter, and I prefer not to use olive oil either. Dampen a paper towel with oil (or swipe it through your can of Crisco) and wipe the fat onto your cast-iron piece. Inside and out is fine, but make sure you don't miss any areas. Next, grab a clean paper towel and wipe OFF as much of what you just wiped on as you can. Thin, thin, thin layer. You know those sites that tell you to put your pan in the oven upside-down so excess oil can drip out? Bogus. There shouldn't be enough oil on the piece to drip. If there is, you're doing it wrong. We're talking a layer of oil whose thickness is measured in angstroms... nanometers... a hundred molecules. Ten thicknesses of the initial seasoning should still be thinner than a sheet of paper.

                3: Bake. 400 degrees F (or 200C) for an hour is a good rule of thumb. Why not 300? 500? Why an hour? Ok, first, what you're doing is actually trying to make the fat (oil) decompose. Fats are basically some hydrocarbon chains hanging onto a few water molecules. At room temperature, nothing special happens, as there's not enough energy around to allow the molecules to react in any way. But add enough heat and the fat molecules will begin to decompose. A water molecule (technically an oxygen atom from the air combined with a hydroxyl radical from the carboxylic acid group for any organic chemistry majors, but we'll keep it simple for this discussion) separates from the hydrocarbon chains and evaporates. This leaves behind the hydrocarbon chains, which tend to link up together (polymerize). Now, as more and more of these hydrocarbon chains link up, the fat (oil) becomes more solid... think of it as turning the Crisco into nylon. But it doesn't (or shouldn't) stop there. The heat allows the carbon atoms to join together, which means a hydrogen atom is 'squeezed out' of the chain of hydrocarbons. This process is called pyrolysys or carbonization.
                Now, all that said.. why 400 degrees? Because lower and the reactions might not happen at all, or just the polymerization will happen (sticky, gooey seasoning), or it'll take too long. Higher temps and the reaction might proceed too quickly. Remember that water evaporating? If the polymerization happens before the water (steam) can escape from the thickening fat, it'll stay trapped and form bubbles. Same way steam makes baked goods rise, except you want your seasoning layer to be more like a tortilla than a hamburger bun. That's also why you want the layer of fat (oil) to be thin. Thick layers trap the escaping gases and become full of bubbles... spongey, soft and not very robust. Also, higher temps mean oxygen from the air is more likely to react with the hydrocarbons and degrade the polymerization. Plus, all ovens vary in their temp accuracy, plus factors like infrared heat from coils, etc. mean any recommendation has to be somewhat tempered by variableness. Now.. all this polymerization and pyrolysis doesn't happen instantly. The molecules must be lined up just right and energy has to be absorbed at the right time for all this to happen. Think of flipping a quarter until you get heads 10 times in a row. You know it'll eventually happen, but it might take a lot of flipping. Now imagine doing this with a million quarters, except that you can flip all million at once. After 10 flips, a few of them will all have been heads... after 100 flips, more.. and after 1000 flips, maybe half will have come up heads 10x in a row. Basically, it just takes time for all this flipping and randomness to give you the results you want... which is all million quarters having come up heads 10x in a row. Same with seasoning. You have to keep the fat at an elevated temperature for long enough for all the polymerization and carbonization to happen. Yes, you can increase the heat (flip the quarters faster!) but remember the gases need to escape without leaving a bubble.
                So... 400 degrees for an hour is just a good general guideline that'll work for almost everyone.

                Oh, and after it's been in the oven for an hour? Turn the oven off and let the pan cool in the oven, slowly, with the door closed. This gives all those reactions more time and saves energy.

                Is there more to it? Well, kinda. Cast iron isn't porous, but if you look at it under a microscope you'll see flakes of carbon embedded in an iron matrix. The seasoning primarily attaches itself to these carbon flakes, which is why it sticks to the pan. Remember my cleaning advice? Anything that prevents the carbon in the seasoning from bonding to the carbon flakes in the iron will make the seasoning more likely to flake off.

                How does the seasoning get thicker? Well, cooking is heat, oil and time, so a wee bit of oil will go through the whole polymerization and carbonization process, adding to and thickening the seasoning. How thick is a good layer of seasoning? No thicker than a sheet of paper or two.

                Can you do additional oiling and baking to add more layers to the seasoning? Sure, but don't go overboard. Two or three initial layers is fine, more is overkill.

                How do you clean it? Is soap ok? Should I use kosher salt, etc? A green 3M scrubbie and hot water is, in my opinion, the best. Kosher salt is recommended because the salt acts as an abrasive, and kosher salt has larger grains that don't dissolve as easily. Why spend money on kosher salt when you probably already have a plastic scrubbie? Basically, anything that's safe to use on Teflon is safe to use on seasoning. As for soap, a properly seasoned pan is IMPERVIOUS to soap. There are no pores to trap soap, and soap doesn't dissolve seasoning. If you doubt it, try washing a piece of anthracite coal. That said, I avoid soap because soap plus the mechanical scrubbing action DOES tend to remove the semi-polymerized coating of oil that will eventually become part of the seasoning. I do however occasionally use soap on my cast iron, but I'm more likely to just wipe it off well with a paper towel and put it away, or scrub with a scrubbie when needed.

                Phew, science!

                4 Replies
                  1. re: ThreeGigs

                    Wow. Is there a way to save that as "Cast Iron 101"?

                    1. re: ThreeGigs

                      ThreeG, I am going to save this as my go-to primer. I'm still struggling with CI seasoning, so will try the above.

                      But some follow-up questions:

                      -- I thought optimal temperature for CI seasoning was dependent on type of grease used/its smoke point? I.e., some types of grease have smoke pts below 300, others above 400..and thought somehow the grease had to get just to (?) smoke pt or above it (??). Can you pls address this?

                      -- Re rinsing well with water -- doesn't the whole (now bare/unseasoned) pan rust instantaneously upon contact with water even if just slightly then (per Chem's earlier post) and then you're back to square one -- having to scrub off the rust that JUST appeared from the rinsing, then rinse off the steel wool bits or whatever you scrubbed the new rust with, then rust comes back with that new exposure to water, etc..? I posted about this once before and don't think I fully resolved it except to think that I might try scrubbing off the rust with just oil and salt so hopefully wouldn't have to rinse with water (assuming rust as opposed to steel wool is somewhat safe to ingest if there are a few remaining bits left in the pan).

                      I do know that I got caught in this vicious cycle, and this was just trying to get rid of a small rust patch on a new pre-seasoned Lodge!

                      Thanks in advance.

                      1. re: iyc_nyc

                        "I thought optimal temperature for CI seasoning was dependent on type of grease used/its smoke point?"
                        It's not smoke, really. It's haze, or smog. Water vapor plus oxides of nitrogen, and the occasional ammonia or methane molecule. If you can see the smoke, you are producing too much of the gases too quickly. Yes, some oils have higher or lower *visible* smoke points, mostly because they are a combination of lipids that decompose at various temps. All fats will smoke at around 350 degrees F, it's just that with some, there isn't a large enough constituent of easily decomposed lipids to be able to *see* the resulting gases. Like a pan of water, just because you don't see steam, doesn't mean the water isn't evaporating.

                        "doesn't the whole (now bare/unseasoned) pan rust instantaneously upon contact with water even if just slightly"
                        Not really. Iron oxide formation takes time, and while you might get a molecule thick layer of rust, it'll get wiped off by the paper towel when you dry it. Any further iron oxide formation will be minimal at most since without water or an electrolytic solution (like SALTY WATER, ahem), rusting happens quite slowly. Also, over time, the seasoning process will tend to pull the oxygen atom off of the iron atom, leaving the iron atom free to re-bond to the cast substrate, or mix with the polymerizing oil where it'll help catalyze the polymerization process. Now, you know salt water causes rust to form faster. And you know that after using oil and salt you'll have to wash with soap and water (I mean, you wouldn't leave *any* salt on the pan while seasoning, right?), meaning that at some point you'll be exposing your bare iron to salt water when the salt dissolves in the water. So put your salt away and scrub with some steel wool or sandpaper to get rid of rust, then wash it, dry it with a towel and then DRY it with heat. Lightly oil and season.