Chemistry of Cast Iron Seasoning: A Science-Based How-To

The post after this one on “black rust” describes why you should heat the pan before applying oil for seasoning. This helps the seasoning to adhere and makes the pan pleasantly black.

In a previous post, I illustrated how I cleaned and reseasoned an antique cast iron popover pan. This was my first attempt, and my seasoning technique was somewhat haphazard because I couldn’t find consistent, science-based advice. I used a combination of organic avocado oil and strained drippings from organic bacon. This worked pretty well on the popover pan, which doesn’t have a polished surface. But the smooth inner surface of a skillet showed an unevenness of color and texture, and the seasoning wasn’t hard enough. It was too easily marred by cooking utensils or scraping against oven racks.

I wanted to understand the chemistry behind seasoning so I’d know how to fix this, but there is nothing that addresses this issue directly. A Web page on cast iron posted by someone similarly obsessed with the science gave me two crucial clues, the phrases “polymerized fat” and “drying oil”. From there I was able to find the relevant scientific literature and put the pieces together.

The pictures below are both of the same antique cast iron skillet. The “before” close-up on the left is from a picture of the skillet in my previous blog post on making German Pancakes. I stripped the pan with oven cleaner and reseasoned it based on my new understanding. The “after” close-up on the right shows the result.

Griswold skillet closeups: old seasoning on left, new seasoning on right
Griswold skillet closeups: old seasoning on left, new seasoning on right

Start With the Right Oil (It’s Not What You Think)

I’ve read dozens of Web pages on how to season cast iron, and there is no consensus in the advice. Some say vegetable oils leave a sticky surface and to only use lard. Some say animal fat gives a surface that is too soft and to only use vegetable oils. Some say corn oil is the only fat to use, or Crisco, or olive oil. Some recommend bacon drippings since lard is no longer readily available. Some say you must use a saturated fat – that is, a fat that is solid at room temperature, whether it’s animal or vegetable (palm oil, coconut oil, Crisco, lard). Some say never use butter. Some say butter is fine. Some swear by Pam (spray-on canola oil with additives). Some say the additives in Pam leave a residue at high temperatures and pure canola oil is best. Some say it doesn’t matter what oil you use.

They are all wrong. It does matter what oil you use, and the oil that gives the best results is not in this list. So what is it? Here are some hints: What oil do artists mix with pigment for a high quality oil paint that dries hard and glassy on the canvas? What oil is commonly used by woodturners to give their sculptures a protective, soft-sheen finish? It’s the same oil. Now what is the food-grade equivalent of this oil?

The oil used by artists and woodturners is linseed oil. The food-grade equivalent is called flaxseed oil. This oil is ideal for seasoning cast iron for the same reason it’s an ideal base for oil paint and wood finishes. It’s a “drying oil”, which means it can transform into a hard, tough film. This doesn’t happen through “drying” in the sense of losing moisture through evaporation. The term is actually a misnomer. The transformation is through a chemical process called “polymerization”.

The seasoning on cast iron is formed by fat polymerization, fat polymerization is maximized with a drying oil, and flaxseed oil is the only drying oil that’s edible. From that I deduced that flaxseed oil would be the ideal oil for seasoning cast iron.

As a reality check of this theory, I googled “season cast iron with flaxseed oil” to see what came up. The very first hit is a page written by a guy who seasons his cast iron cookware with linseed oil from the hardware store because it gives the hardest surface of anything he’s tried. (I’m not sure how safe that is; I don’t recommend it.) Below that were several sites selling traditional cast iron cookware from China, which they advertise as being “preseasoned with high quality flax oil”. I don’t know whether they really use food-grade flaxseed oil (which is expensive) or linseed oil from a hardware store. What’s significant is the claim. Seasoning with high quality flaxseed oil is something to brag about.

With this encouragement, I stripped one of my skillets and reseasoned it with flaxseed oil. As you can see in the picture above, the result was a dramatic improvement. The finish is smooth, hard, and evenly colored.

Seasoning Is Not Cooking: Different Principles Apply

The first time I seasoned a pan I chose avocado oil because it’s monounsaturated and doesn’t easily go rancid. It also has the highest smoke point of any edible oil, 520°F, so I could heat it in a 450°F oven without passing the smoke point. I knew that when cooking, you should never heat an oil past its smoke point because that causes the release of “free radicals”, which are carcinogenic. I was careful not to choose a polyunsaturated oil – and especially not an oil high in omega-3 fatty acids – because these are especially vulnerable to breakdown with heat and the release of free radicals.

Ironically, it’s for exactly these reasons that the best oil for seasoning cast iron is an oil high in omega-3 fatty acids – in particular, alpha-linolenic acid (ALA). Free radicals are actually what enable the polymerization. Drying oils, which produce the hardest polymers, are characterized by high levels of polyunsaturated fatty acids, especially the omega-3 fatty acid ALA.

The lard that was traditionally used for seasoning 100 years ago was much higher in ALA than fat from pigs today, because back then pigs ate their natural diet. Today they are raised on industrial feedlots and forced to eat grain, making their fat low in omega-3s.

Since lard is traditional but no longer readily available, many people substitute bacon drippings, but this is a bad idea. If it’s conventional bacon, you’re baking in carcinogenic nitrates. But even organic bacon is not good for an initial seasoning because it’s filled with salt.

The reason that Pam seems to work well in seasoning is that its main ingredient is canola oil, which is relatively high in ALA (10%), making it a “semi-drying oil”. Flaxseed oil, a drying oil, is 57% ALA. But it’s not a good idea to use a spray oil, no matter what oil it’s made with, because of its additives. You’re doing chemistry here. If you want good results, use pure ingredients.

Fat polymerization can be triggered or accelerated in a variety of ways. As best I can tell from my reading, the cast iron seasoning process is an example of “radical polymerization”. The process is initiated when something causes the release of free radicals in the oil. The free radicals then “crosslink” to form the tough, hard film you see in a well-seasoned pan.

So what is the “something” that initiates the release of free radicals in fat? Iron, for one thing. High heat, light, and oxygen, for some others. To prevent cooking oils from going rancid – i.e., breaking down and releasing free radicals – you need to store them in dark, tightly sealed containers in a cool location. To initiate or accelerate the release of free radicals, put the oil in contact with bare iron and heat it above its smoke point, which will cause even non-drying oils to release free radicals.

I haven’t defined “free radical” or “crosslink” because that gets into details of chemistry that you don’t need to understand to season a cast iron pan. All you need to know is that the molecular structure of the oil changes and becomes something else, something tough and solid. The process is initiated with the release of free radicals, which then become crosslinked, creating a hard surface.

Free radicals are carcinogenic inside your body, and also a cause of aging. So don’t ever heat oil you’re going to eat above its smoke point. If the oil starts to smoke, toss it out and start again. When you’re seasoning a pan, you’re not cooking food. By the time the seasoned pan comes out of the oven, there are no more free radicals.

The Recipe for Perfect Cast Iron Seasoning

The basic idea is this: Smear a food-grade drying oil onto a cast iron pan, and then bake it above the oil’s smoke point. This will initiate the release of free radicals and polymerization. The more drying the oil, the harder the polymer. So start with the right oil.

Go to your local health food store or organic grocery and buy a bottle of flaxseed oil. It’s sold as an omega-3 supplement and it’s in the refrigeration section because it goes rancid so easily. Check the expiration date to make sure it’s not already rancid. Buy an organic flaxseed oil. You don’t want to burn toxic chemicals into your cookware to leach out forever more. It’s a fairly expensive oil. I paid $17 for a 17 ounce bottle of cold-pressed, unrefined, organic flaxseed oil. As it says on the bottle, shake it before you use it.

Strip your pan down to the iron using the techniques I describe in my popover post. Heat the pan in a 200°F oven to be sure it’s bone dry and to open the pores of the iron a little. Then put it on a paper towel, pour a little flaxseed oil on it (don’t forget to shake the bottle), and rub the oil all over the pan with your hands, making sure to get into every nook and cranny. Your hands and the pan will be nice and oily.

Now rub it all off. Yup – all. All. Rub it off with paper towels or a cotton cloth until it looks like there is nothing left on the surface. There actually is oil left on the surface, it’s just very thin. The pan should look dry, not glistening with oil. Put the pan upside down in a cold oven. Most instructions say to put aluminum foil under it to catch any drips, but if your oil coating is as thin as it should be, there won’t be any drips.

Turn the oven to a baking temperature of 500°F (or as high as your oven goes – mine only goes to 450°F) and let the pan preheat with the oven. When it reaches temperature, set the timer for an hour. After an hour, turn off the oven but do not open the oven door. Let it cool off with the pan inside for two hours, at which point it’s cool enough to handle.

The pan will come out of the oven a little darker, but matte in texture – not the semi-gloss you’re aiming for. It needs more coats. In fact, it needs at least six coats. So again rub on the oil, wipe it off, put it in the cold oven, let it preheat, bake for an hour, and let it cool in the oven for two hours. The picture above was taken after six coats of seasoning. At that point it starts to develop a bit of a sheen and the pan is ready for use.

If you try this, you will be tempted to use a thicker coat of oil to speed up the process. Don’t do it. It just gets you an uneven surface – or worse, baked on drips. Been there, done that. You can’t speed up the process. If you try, you’ll mess up the pan and have to start over.

The reason for the very hot oven is to be sure the temperature is above the oil’s smoke point, and to maximally accelerate the release of free radicals. Unrefined flaxseed oil actually has the lowest smoke point of any oil (see this table). But the higher the temperature the more it will smoke, and that’s good for seasoning (though bad for eating – do not let oils smoke during cooking).

I mentioned earlier there’s a myth floating around that vegetable oils leave a sticky residue. If the pan comes out of the oven sticky, the cause is one of three things:

  • You put the oil on too thick.
  • Your oven temperature was too low.
  • Your baking time was too short.

It’s possible to use a suboptimal oil for seasoning, like Crisco or bacon drippings, and still end up with a usable pan. Many (most) people do this. But the seasoning will be relatively soft, not as nonstick, and will tend to wear off. If you want the hardest, slickest seasoning possible, use the right oil: flaxseed oil.

Editorial Note:

Many flax oils contain added ingredients to prevent rancidity, and it’s the tendency of this oil to go rancid that makes it so good for seasoning pans. Flax oil only works if it’s 100% pure flax oil with nothing added, so read the ingredients! People have reported mixed results, and this is probably why.

493 thoughts on “Chemistry of Cast Iron Seasoning: A Science-Based How-To

  1. Thanks for sharing! Do you think the same process would work on cast iron Wolf gas cooktop grates? I’ve first got to find a way to get the acidic tomato sauce off the cast iron. Thanks!

  2. Sheryl, Okay… awesome site. Now you need to find a way of locating us before we do it wrong! I missed but think I was on the right track when I select the Publix store-brand peanut oil. Edible, high smoke point, etc. Close but not quite. So, I scrubbed my neglected double-sided cast iron pancake skillet / grilling pan. It had been living in our carport since 2009, exposed to Key Largo’s salty, humid air. So, I put it in a tray lined with a heavy plastic bag, and covered the skillet with white vinegar for 15 minutes. Then I got called away for a few minutes…

    A week later, I opened the bag and a head of brown foam stood an inch above the vinegar. I flipped it and both sides looked about the same. Using a stainless grill brush I scrubbed at the rust until 99% was gone, though there were still some tough to reach gutter corners.

    I dried it with paper towels, and then wiped on peanut oil immediately as a rust-inhibitor, and put it in the oven at 200 degrees… until my wife came home and hour later and asked “what is that stench?” Did I mention having no sense of smell?

    So, now what? I can find flaxseed oil, but do I need to start over?

  3. Great! Awesome! I have a cast iron 12 inch I just love, but didn’t know what to re-season it with since as you know nothing really worked right. I am ready to find some flax seed oil today! Thanks!!!

  4. Amazing. Thank you for doing this homework and posting it to the benefit of all. I’ve been told that canola oil is the best, and now that I (superficially) know the science behind why a few people think that’s true, I’m sure flaxseed oil will work ever better.

  5. For Mario – Appreciate the post and the link to the PDF. I’m confused where you mention “The “metallic catalyst” in our case is the very iron we’re trying to season” and yet when I look at “(iii)” of the PDF you reference as the significant conclusion relating to the cast iron we’re dealing with it says, “W I T H O U T the addition of Metallic catalysts”… what am I misinterpreting? Thanks.

    To All: I used Sheryl’s method (with the flaxseed and 500 degrees for an hour + the cool down/per coat) for 5 pans and a griddle and it seems to have worked well. Whether a cheaper oil would have worked as well as some have suggested I don’t know. I just know that after all the work I was pleased with the results. Seems to me that the thin and multiple layers were the key. I did 12 coats for 2 pans and 6 coats for the rest and I can’t tell any difference between them in the results. RESULTS: Sometimes a little sticking with eggs (always using a little oil or butter) but seems to be much better when laying down a little salt and pepper before the eggs. But any sticking in anything I’ve tried in any of the pans is usually easily cleaned with a small pass over with a Teflon (or I suppose metal which I have not used) spatula. In tougher cases water cleanup with or without soap and a light rub with cloth or scotch brite if needed is no issue as there is absolutely no metal exposed.

    Thanks Sheryl.

  6. I was wondering if anyone had any comments about the free radicals released into the air the seasoning process, and also, if there was any information about consuming the seasoning layer with regards to ingesting carcinogens. We are avoiding the nonstick pans because of the chemicals, but on the other hand, burned food (some even say seared food) is supposedly carcinogenic.

    It’s not that I’m scraping the seasoning layer off for snacks, but it does seem to chip off during the cooking process sometimes.

  7. Hi Sheryl,

    I tried this seasoning process and it seemed to work until I cooked with, and then washed my pans. The season washed right out. I’m not sure what happened. I just washed with hot water and scrubbed with a plastic scrub brush. When I dried it, the towel turned black and the season was no longer in the pan except a few little spots.

  8. This process worked beautifully for me. It has been about two weeks since I re-seasoned my cast iron pan. Since then I’ve cooked all kinds of things in it: fried eggs and omelettes, fried rice, corn bread, and a nicely seared steak. There has been absolutely no sticking, and the black coating has remained intact and unchanged.

    I don’t know why it worked for me but failed for others. I’ll provide some details of what I did. I first cleaned the pan using the electrolysis method which is referenced in Sheryl’s article. I changed the electrolyte twice during the process. After the first round of electrolysis (pan on top), the bottom of the pan was clean but the top/inside was still fairly black, so I stacked the anode on top of the pan for the subsequent two rounds. I then washed the pan with dish soap and hot water, rinsed it thoroughly, dried it quickly and applied the oil immediately.

    I followed Sheryl’s method exactly, more or less. I used organic flax-seed oil, and really wiped off as much as I could – the pan was barely oily to the touch – before baking it on. I did six layers over 3 days; I just didn’t have time to do all six layers non-stop. To my thinking, that shouldn’t be a problem; extra time means more oxidation and cross-linking. I baked to 450F, sometimes 500F.

    The only other change I made to the process was the following. I was thinking about the seasoning flaking off, and about avalanches. In order to prevent flaking, I reasoned, you want the bottom layers to be harder than the layers above. Seasoning a pan the traditional way, on a stove-top, would achieve this automatically, but baking the pan face-down might not. So, after the first few layers were baked on, I baked the pan a bit longer in an upright position (bottom element on) after each layer.

    The result is the best “non-stick” pan I’ve ever had. If you’re trying this (again), I encourage you to follow Sheryl’s advice: get the pan absolutely clean down to the bare metal before starting; wipe off as much oil as you can before baking. And think about giving it some extra time in the oven, heating from the bottom. It might help.

    Good luck all,

  9. i have a somewhat rare griswold skillet lid,i have it cleaned to the bare metal,the end result,im looking for is a nice black color,,,,will your method of using flaxseed give me the results i desire and how many coats do u feel i will need?

  10. @Mario:

    Sounds like you may be on to something here, that paper is a great find. But @Bill is correct when he says that the line you cite mentions oil without the catalyst, which conflicts with your assertion that the cast iron would act as a catalyst in our case.

    The good news is, I think you’re wrong about the catalyst part and right about everything else! 😉 The catalysts they use in the paper are calcium, cobalt, and zirconium and are added to the oil before applying the oil to a steel plate. I believe these metals are like the drying agents that would be added to hardware-grade linseed oil. So their conclusion about the oil without catalysts is the one that applies to us after all.

    I still need to better understand parts of the paper (it mentions that although thermal polymerization of linseed oil begins at 200C, hard-bodying begins around 240C and cross-linking doesn’t start until 270C. I thought cross-linking was good!? And the paper doesn’t explain hard-bodying at all. So if anybody can explain or has links to further reading it’d be much appreciated!). But as I say it looks like you may really be on to something, so thanks for posting!

  11. Hello Sheryl,

    I love this article. I did the same sort of things you mentioned, confusing oils that are good for cooking with oils that are good for seasoning, and gave up on one of my old cast iron dutch ovens. I will have to try your method.

    I do have one potential enhancement to your method though. You used unrefined flax seed oil that had to be shaken because it has the lowest smoke point of any edible oil; I would contend that for seasoning, one would want to use highly filtered and non-chemically refined flax seed oil for the following reason: the coating that forms the seasoning is polymerized oil—only the oil polymerizes. Anything that settles in the bottle that needs to be re-suspended by shaking consists of non-oil components such as lignin, fiber, and other debris. These almost certainly lower the smoke point (just as most unrefined oils have lower smoke points), but they don’t contribute beneficially to seasoning; rather than polymerizing, they just char.

    My hypothesis is that if you use a refined flax seed oil, or just pour the oil off the top to avoid sediment, or filter all the non-oil suspended debris out, you’ll get to the fine sheen in fewer coats. I suspect the tiny particles of non-oil components give the seasoning a matte finish since char particles have a matte texture, whereas polymerized oil is strictly glossy, as is seen from the use of refined linseed oil for varnish.

    I won’t have the opportunity to test this hypothesis for a while. If you have a chance to test it, I would love to see whether this turns out to be true.

  12. Hi Sheryl,

    Love your blog. I have always loved cast iron cooking but never had success in seasoning it to a Non-stick. I was eager to try flax seed and your procedure. The only flax seed oil i was able to find was sold on the shelf with olive oils and clearly states “no refrigeration required”. The stuff said pure flax seed oil, and the only ingredient is “flaxseed oil”

    why is my flaxseed oil different? Should I be using this?

  13. Hi Sheryl,
    Just finished seasoning my cast and carbon steel pans with your method. The results are outstanding.
    This is the best method I ever used and a bottle of flaxseed oil will last a long time.


  14. Hi Sheryl
    Chemistry of Cast Iron Seasoning is great. Just finished removing old and reseasoned two #12 Dutch Ovens, a #10, and a #10 Grisoald frying pan that I just picked up at a flea market for a song. The whole process took me a week. Followed all instructions to a T. All turned out great. After checking quite a few healthfood stores for Flaxseed oil. I stumbled across it in Walmart 7oz for about 5 bucks.
    Thanks for a great article.

  15. Hi Sheryl,

    I just bought an Oster Cast Iron Casserole ( The instructions for seasoning suggested using vegetable oil. Without doing proper research, I used vegetable oil and put the casserole dish in the oven at 350 for an hour. When it came out it was a sticky mess. I searched and found that possibly it wasn’t in the oven long enough. I put it in for about 45 minutes and it came out worse. Did I ruin it? If not, how do I remove the sticky residue?


  16. Sheryl,

    I have several Lodge pieces. They don’t need stripping, just re-seasoning. Can I use your method without stripping completely down to bare metal? If so, should I prep the pans?

    Thanks for the interesting information.


  17. Hi Sheryl,
    Thanks for the great reading,I’ve learned a lot. My question is==== what do you think about media blasting ( sand,iron oxide,glass bead ) to strip the cast iron?

  18. Hello, I have a few questions and hopefully I can get some help
    First time cast iron user, bought Lodge and I’m in the middle of your tutorial.

    -when heating pan in oven and then placing on the electric glass top to make a steak, do you have to put it on a pre-heated burner ? I’m afraid the glass top might crack from putting heated pan onto unheated top.
    -after every warm water wash, do you oil only inside of the pan, or do you oi the whole pan ?
    -seasoned pan has oil on the bottom aswell, so when you put it on the burner does the oil burn, like putting oil between a burner and pot/pan ?

  19. You’ve helped me understand a lot of things even though I’ve been ‘seasoning’ cast iron woks for years as a business! I’m not a scientist or culinary expert, so finding your ‘scientific’ explanations very informative. I’m definitely going to try using flaxseed oil to see if it works on a lightweight, thin walled cast iron wok from China. The woks come with some grey dust powder to prevent rusting during shipping. If you don’t clean it out properly initially and then ‘season’ it, it makes people very sick because you’ve in essence burned it into the wok! My husband and I were so anxious to make sure these woks were truly cast iron that we sent it off to Lodge for a material test and their President called to say how amazed he was that it could be so thin and cast iron! I’ve read so many articles/forums/posts about this topic it makes my head spin. But yours makes sense and you’ve got proof it works, so thanks for the info.

  20. Ok, so I stripped my irons down, put on the oil and popped them into the 500 degree oven. Smoke poured out from the top burners within 10 minutes! Not sure what I did wrong but could really use some advise. Thanks so much!

  21. Hi Sheryl,
    I appreciated your advice about seasoning pans with oil because you care about safety and health.
    I just wanted to add that we now understand that omega 3 is beneficial for us, however the oils that are recommended for cooking and eating with omega 3 also have large quantities of omega 6 –example, canola oil. It is dangerous to have an overbalance of omega 6 in our diet. Most oils, again canola, sunflower, corn for sure!, are processed, that is heated, which begins the chemical breakdown of these oils and rancidity all before they hit the store shelves — even though they don’t have a strong rancid flavor the process has begun! This is also dangerous to ingest. Best sources of fat to use in cooking (low or no omega 6, contain omega 3s, and are not processed with heat) are olive oil, butter, avocado and coconut oil.

  22. I use walnut oil-based paints because they clean-up with oil instead of solvents. I know walnut oil is a drying oil because the canvases dry in a day or two and walnut oil is edible (usually used as a salad oil). Any comments?

  23. Wow, I love this article. It kills me that it took me so long to find it – I’ve spent hours researching how to season my cast iron and find so much anecdotal evidence – but this is the first true scientific explanation, which absolutely fascinates me and satisfies my curiosity. I’ve already had one unsuccessful round of seasoning (could have been any number of mistakes on my part – but it ended up rusting). It was discouraging, but I’ll definitely try again after this.

    Thank you so much.

    No one in my family uses cast iron, so I had a few pointers to begin with.

    Casey – it sounds as though you must have had too much oil on your pan. Or possible an already dirty oven, with the smoke coming from food spills? (no judgements here, just curious). Also, I believe Sheryl noted (somewhere?) that the smoke point of flaxseed oil is around 225 degrees – and the author says she used 450, so you might want to try 450 next time. But to quote the original article: “the higher the temperature the more it will smoke, and that’s good for seasoning,” so 500 is probably your best bet.

  24. Casey – also – the author does specify to put the pan in a cold oven and let the pan preheat with the oven. Sounds as though you started with a hot oven.

  25. I completed this process putting 6 coats on, but my pan was a bust. I fried an egg using lots of olive oil as I suspected that it needed it. The egg stuck and left a real mess. Had to scrape and scrape and boil water in the pan to try and get it off. Still there is a slight residue. I suspect my problem is that I literally followed Sheryl’s advice. I removed All of the Flax Oil before baking in the oven at each step as she suggested. All along the way and at the end of the process, I had no shine at all in my pan. You suggested that there should be no shine after the oil was removed, but you implied that at the end there would be a bit of a shine. I had none, maybe because I followed your advice and removed ALL of the oil each time. I’ve read through these comments all of them on your site and its apparant that this has not worked for a lot a people. Any ideas?

  26. I have an interesting chunk of cast iron that I got from a foundry tour. It looks a bit like some strange, giant fish fossil, and for years I’ve been enjoying it as a sculpture. It has been rusty for several years, and, on a lark, I decided to “season” it.

    I didn’t do anything fancy and use avocado oil or flax oil, but instead used some olive oil I had in the cupboard. Since I’m not going to cook with it, I wasn’t worried about getting a perfect seasoning. However, the color is more of a metallic dark brown, and not a black. Is this due to the oil I used, or because the casting is about 2 inches thick in places, so it needs to be baked at a much higher temp than my oven can produce?

    I’m sure it’s a combination of all the above, but I’d like to try to get it blacker. Would it be possible to add a coat of flax seed oil on top of what I’ve done, or should I try to strip the oil off it first?


  27. Hello! Thanks so much for this article! I am looking to buy my first cast iron pan and I am wary of buy “pre-seasoned” pans, and somehow came across this when I was trying to figure out how they actually “pre-season” them.

    Anyway, I have two questions: (hopefully they weren’t already asked and answered, there are a lot of comments and I haven’t had a chance to read through them all)

    1. Do you know of any health effects from the polymerized fats? I’m concerned that it may not be safe. I paint as a hobby and the idea of eating off a surface that has essentially a layer of glaze on it does creep me out a bit (even if created from food grade flax oil). Do you know of any research on the subject? But with that in mind, I’m sure it’s probably much safer then teflon!

    2. Is the layer still porous? As in does some of the iron leech out into your food? One of the benefits of cast iron is the added iron in your diet.

  28. Brad, I used Flax oil on a normal pan and mine also came out with a metallic like dark brown color.

  29. Amanda, I had some of the same concerns. We are being taken back to cast iron because we are concerned about the teflon surfaces, and the question is why should we be any less concerned about creating our own teflon-like surface on cast iron. Specifically when I bought my bottle of Flax Oil to start this process, the first thing I read on the bottle is “Do Not Heat this Product”.

    I think a layman’s blog is maybe not the definitive answer as to the health risks if any of this, and also homemade research into the best oil to use may leave something to be desired as well.

  30. Hi Sheryl

    I was fascinated by the post, so i gave it a try

    I had 3 Lodge Cast Iron Pans, 8″ 10″ 12″.

    Cleaned all with the oven cleaner, preheated, put flax seed oil, wiped it clean with cotton cloth, baked it at 500F for an hour, left it for 2 hours, and reapeated that 6 times.

    however, I tried to cook an egg, It sticks like crazy.

    No idea where it went wrong.

    Any idea?

  31. I also tried following the instructions here quite closely. I photographically documented my efforts here.

    It seems that the seasoned surface is not adhering. I mechanically polished the surface down to shiny bare metal and then did 6 rounds in the oven at 500deg. But when I started cooking on my griddle the seasoning seems to be coming up, leaving the surface bare and causing food to stick greatly. The only thing I can think of that I might have done wrong is to forget to shake the bottle of flax oil before applying.

    I am wondering if truly polishing down to bare iron is what people are doing. Short of grinding wheels I’m doubting you’re really getting down beneath all old seasoning and oxide layers to absolutely bare metal. As such I’m wondering if I’ve just damaged my griddle.

  32. I am in the middle of using this process with my new Lodge Signature pan and I wanted to give a warning. I’ve done one cycle at 500 degrees and my stainless steel handles have discolored. So I’m doing the rest at 400 degrees. Be warned! This technique may discolor stainless steel! Not a huge deal functionally, but one of the reasons I bought the signature is because is looks nice. or at least looked nice 🙁

  33. Beom, one thing that seems to happen to folks is they put the oil into the pan right away and heat it up along with the pan. This causes sticking in most pans, including cast iron. One tip to consider is the Chinese cooking proverb: “Hot wok, cold oil, food won’t stick.” That means to heat your dry (but seasoned) pan before you add the oil, then put your oil onto the hot pan and let it heat for about one minute. The surface of the oil will ripple and just barely begin to smoke, and that’s when you add your egg.

  34. You’ve researched and focused a lot on how to get an even, long-lasting seasoning on iron cookware, but haven’t addressed why, if at all, flaxseed oil is the best culinary choice from a results & flavor perspective, which is half of the point of seasoning one’s cookware. See: Wok hei effect

    Wouldn’t it make more sense to season your pans with the best tasting oil, even if it meant having to reseason more often?

  35. I had the same problem as Kevin MacDonald.

    Followed the instructions to a T and had the most gorgeous, slick looking de Buyer carbon steel pans one could ever hope to see.

    After the first cooking session, half the finish came right off. I lost the rest of it with the next cooking.

    Lots of time and effort wasted on a beautiful seasoned finish that didn’t hold to the pan.

    Crisco here I come!

  36. You’ve researched and focused a lot on how to get an even, long-lasting seasoning on iron cookware, but haven’t addressed why, if at all, flaxseed oil is the best culinary choice from a results & flavor perspective, which is half of the point of seasoning one’s cookware. See: Wok hei effect

    Wouldn’t it make more sense to season your pans with the best tasting oil, even if it meant having to reseason more often?

    Seasoning is polymerized fat. It imparts no flavor. Read that link you posted again. It’s the caramelization and Maillard reactions that give the flavor – the stuff that’s being cooked in the seasoned pan, not the seasoning itself.

  37. I’ve always seasoned my cast iron with bacon grease, but was doing some Googling this time to see what others say. I stumbled here and I’m glad I did. Thank you for this. Mmmmmmmm, science!

  38. Thank you Sheryl!!
    Great stuff…I was told by an experienced woodman that ‘boiled linseed oil’ from the hardware store contains hardening chemicals that include heavy metals! It is for this reason that boiled linseed is not recommended for children’s furniture. The linseed available at art supply stores is more pure and expensive product, but I am unsure as to its suitability for food. (perhaps this is all covered in other posts)

  39. I do not want to make a habit of repeating what I said in my original blog post and I’m not going to keep doing it. I am only responding to the last couple of comments because they make dangerous suggestions.

    Do NOT use Ajax or Comet on your cast iron cookware. That is NOT what is meant by “washing soda”. See the original article for what washing soda is. It can be found in the cleaning section of the grocery store.

    ONLY use food grade flaxseed only, found in GROCERY STORES, as it says in the original article. DO NOT use linseed oil from hardware stores or art supply stores. Those may have toxic additives and are dangerous to use on cookware.

    The very first line of the blog post talks about the issue of adherence, which many people have commented about:

    The post after this one on “black rust” describes why you should heat the pan before applying oil for seasoning. This helps the seasoning to adhere and makes the pan pleasantly black.

    This is all the repeating I want to do. I don’t want to close comments. I like keeping the discussion open so people can share ideas, but I don’t want people to make suggestions that will endanger others’ health or destroy their cast iron cookware. I ask that you READ the original article before posting suggestions.

    Thank you.

  40. I am in the process of restoring and seasoning 11 pieces. I have appreciated this information so much. I didn’t see any posts about concerns in breathing the air as the cast iron is heating in the oven. The house is somewhat smokey and the air is strong, a little like when it is in self-cleaning mode. Are there any health concerns for my family breathing this during processing, whether windows are open or closed?

    Thanks anyone!

  41. After pissing around with a Lodge griddle for a year (off and on) and never getting it quite “right”, and reading too many sites and instructions on seasoning, please people, following these directions!!! I have FINALLY ACHIEVED SUCCESS WITH THIS METHOD!!!

    I had tried lard, Crisco, and vegetable oil and made too many mistakes. Spend the money, get the Flaxseed oil, use thin coatings and follow the directions …..IT WORKS!!! Be patient and do it over several days, over and over, coat after coat, and you WILL GET THE SMOOTH BLACK COATING!

    Thank you Sheryl!

  42. I am now using a self cleaning oven to clean up my Griswold cast iron. Before I used lye to clean iron and then washed good with soap and water before seasoning. Does anyone know if a piece that comes out of the oven after cleaning needs to be washed before the seasoning is applied???

  43. I am so excited to use your method and purchased flaxseed oil at Wal-mart yesterday but I am slightly concerned.

    I bought Spring Valley Organic Flax Oil and it only cost about $5.00 for 8 ounces. after what you said about cost in the original article, about $1 an ounce do I have the wrong thing?

    They call it flax oil but the only ingredient listed is Organic Flaxseed Oil.

  44. Sheryl, I have a question. I have been trying your method of seasoning and haven’t had much success. I followed your instructions but when I use the pan to make eggs they always stick. My question is , could my baking temp be too high when I bake the pan for an hour , the thermometer reads 550-600 F degrees. or could I be cooking with too high a temp ? I am using ” Finest Natural ” Flax oil from Walgreens

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