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.
http://sherylcanter.com/wordpress/2010/02/black-rust-and-cast-iron-seasoning/
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
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.
Kyle:
Very interesting post Sheryl!
I have a question though: I was under the impression that once you heat an oil to much past the heat point and it’s done polymerizing it begins to carbonize, loosing the slick surface were after. If that’s the case wouldn’t the flax seed oil have to low of a smoke point, and baking it at 400 degrees bake it past the polymer stage?
January 29, 2010, 6:01 pmSheryl Canter:
Hi Kyle. Temperatures have to be way above 400-500 degrees to burn off polymerized fat. You can observe that just with the spatter mess that builds up in an oven. That’s polymerized fat. Once the chemical conversion to polymer has taken place, it’s not oil anymore and has a different burning point. A self-cleaning oven will burn the seasoning off cast iron (and the polymerized fat in the oven itself), but that’s 900-950 degrees.
January 29, 2010, 6:17 pmJosh:
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.
Now, you’re certainly heading down the right path with linseed oil, with an iodine value of around 185. Fish oils like sardine are up there too. (I’m sure you’ve heard that oily fish like salmon and sardines are rich in omega-3s.) The best oil available for cheap at any grocery store is soybean oil, with an iodine value around 130.
A couple links:
http://www.journeytoforever.org/biodiesel_yield.html#highiodine
http://vegburner.co.uk/oils.htm
January 30, 2010, 9:24 pmSheryl Canter:
Hi Josh. I’d read about iodine values, but it was just one more thing to explain in an article that was already long, so I left it out (though you explained it very succinctly!).
Thanks for the links. I wish canola oil was in the table with the iodine values. I’m pretty sure that’s higher than soy oil. I found a link with another table at one point, but I can’t find it again to save my life. Both canola and soy oils are semi-drying. But yes, soy is cheaper, mostly because of the massive government subsidies for corn and soy (but don’t get me started on that…).
January 30, 2010, 9:44 pmJosh:
Actually, canola is in all those tables – it’s also known under the less marketing-friendly name rapeseed oil.
January 30, 2010, 10:34 pmSheryl Canter:
Ah – there it is. I was skimming for the letter “c” (which I think is for “Canada”, isn’t it?).
Interesting – soy oil has a higher iodine value than canola. I knew sunflower oil was high because I’ve seen it mentioned in research papers on polymerization. But sunflower oil is very high in omega-6s and low in omega-3s, as I recall. So you’re right – omega-3 content is not the most direct measure!
Someone sent me a link yesterday that talked about the importance of carbon being bound up in the polymerized fat for slickness, but I don’t understand why that would make a difference. Polymerized fat is already very hard and slick. Someone just stated it in a forum post without explaining why, so I don’t know if it’s true.
January 30, 2010, 11:07 pmChris:
Sheryl,
February 13, 2010, 1:29 pmThanks for this. I am trying it out right now and I followed all your directions. My first coat came out gray with black spots. It looks dry, almost as if I didn’t season it except there are those spots. I did bake it at 550 for an hour. Also, I used a very thin coat of canola oil to keep it from rusting after I cleaned it initially. My flaxseed oil is filtered, cold-pressed from whole foods. I tried another coat this morning and it is cooling in the oven now. Do I need to start over? Thanks!
Sheryl Canter:
Chris,
It almost sounds like the pan wasn’t completely dry before you oiled it. I always dry the pan for a few minutes in a 200 degree oven before oiling, to make sure it starts out bone dry. Do you think it might have been damp when you put on the oil?
- Sheryl
February 13, 2010, 6:04 pmChris:
Sheryl,
February 14, 2010, 12:06 amActually, yes it may have been damp. I did dry it with a towel, but I didn’t put it in the oven before putting the canola oil on after my initial cleaning. I did put it in the oven at 200 before doing the flaxseed oil regiment.
Sheryl Canter:
That’s definitely the problem, then. Water will prevent the oil from adhering. You also could get rust beneath the seasoning if the pan wasn’t completely dry. That could ruin it, so I’d strip it again, make sure it’s bone dry (at least 10 minutes in a 200 degree oven), and then oil it for seasoning.
Or better yet, heat it stripped and unoiled in a hot (450 degree) oven for an hour to darken the pan with what I believe is “black rust”. I’ve started doing this. Just did it, in fact – the pan is still in the oven. Here’s a link with more info about black rust:
http://sherylcanter.com/wordpress/2010/02/black-rust-and-cast-iron-seasoning/
February 14, 2010, 12:33 amChris:
Thanks, stripped it down using the self-cleaning oven method this time, the lye is just too gross. It worked much better and faster! I just finished wiping all the ash off and put it in vinegar and water then rinsed with soda water and then regular water. Now it is in the oven baking at 450 for an hour. We’ll see if it works!
February 14, 2010, 7:23 pmSheryl Canter:
I don’t have a self-cleaning oven. But even if I did, I’d be a little nervous about using it because the high heat could warp the pan. I use oven cleaner with lye. I hated doing it at first because the lye made me so nervous, but after having done it a bunch of times now, it’s no big deal. It takes just a minute to spray it, I seal it in a plastic bag for a couple days, then rinse it off and give it a quick wash. Usually it doesn’t require much more than that.
I just seasoned a new gem pan yesterday – or rather, new to me. The pan was made by Griswold between 1890-1910, and it’s in great condition. I did the one-hour at 450 thing (no oil), then three coats of flaxseed oil. The only time I put the oil on hot rather than letting the pan cool in the oven first was after the initial no-oil baking. I have an idea this opens the pores of the iron, but I can’t say for sure that’s true. In any case, the pan came out great. Here are pictures, taken right after I finished seasoning it (no additional oil afterwards – this is the natural sheen from the seasoning). Today I made oatmeal scones in the pan and they slid right out.
February 14, 2010, 7:50 pmChris:
nice! I did the bake at 450 for an hour today on a bare pan and it did darken. I wiped some flaxseed oil on it after it cooled enough to handle and the paper towels keep on looking like they have stuff on them. They get grey on them from the inside of the pan and they get brown stuff from the outside. Is this normal?
February 14, 2010, 10:21 pmSheryl Canter:
> I wiped some flaxseed oil on it after it cooled enough to handle and the paper towels keep on looking like they have stuff on them. They get grey on them from the inside of the pan and they get brown stuff from the outside. Is this normal?
Yes, that’s normal for naked iron. What you’re actually seeing is iron, rubbing off onto the paper towel. If it’s slightly brownish, there might be some flash rust mixed in. Once it has a layer of seasoning, this no longer happens.
February 15, 2010, 12:07 amkatie:
just curious . . . can you use lard, if you have it? I rendered some pork fat and was going to use that. It’s what my great Grandma swore by?
February 24, 2010, 11:20 pmSheryl Canter:
Sure, lard is fine. If it’s from naturally fed pigs like your grandmother had access to, even better. Naturally fed pigs have fat that’s higher in omega-3s and produces a harder seasoning.
Really any fat will work fine as long as it doesn’t have a lot of additives (like bacon fat does). Some fats produce a harder seasoning than others, that’s all.
Don’t forget to heat the pan first, as described in the next post. This is important.
http://sherylcanter.com/wordpress/2010/02/black-rust-and-cast-iron-seasoning/
February 25, 2010, 8:34 amJohn:
Great read! I’m having problems finding flaxseed oil. I prefer to buy on the internet because of my rural location. This is an Amazon search and I would like to know if any or all of these are the right thing to buy: http://www.amazon.com/gp/search/ref=sr_nr_n_0?rh=n%3A16310101%2Ck%3Aflaxseed+oil%2Cp_76%3A1249146011%2Cn%3A%2116310211%2Cn%3A123382011&bbn=16310211&keywords=flaxseed+oil&ie=UTF8&qid=1267464416&rnid=16310211
Thanks!
March 1, 2010, 12:32 pmSheryl Canter:
Hi John,
Any food grade flax oil is fine – the one you link to is fine. Just don’t use linseed oil from a hardware store!
- Sheryl
March 2, 2010, 9:28 pmJill:
Hello Sheryl,
I have loved reading your entries about your experiments with cast iron cookware. I have enjoyed them so much that I have bid on a few Griswold items on ebay and hope to have a few pieces soon! I am excited to begin the cleaning/seasoning process.
Once your cast iron cookware has been seasoned, how do you clean it after cooking a meal? I read that a lot of people never use detergent while others say detergent is okay. Do you re-oil after cleaning?
Thanks for all the great information.
March 2, 2010, 9:30 pmSheryl Canter:
Somebody posted some great feedback on this seasoning method in another forum. I’ll quote the message, and also link to it:
http://www.permies.com/bb/index.php?topic=3385.msg28406#msg28406
March 2, 2010, 9:31 pmSheryl Canter:
> Once your cast iron cookware has been seasoned, how do you clean it after cooking a meal? I read that a lot of people never use detergent while others say detergent is okay. Do you re-oil after cleaning?
Hi, Jill. Glad you liked the articles!
I handwash my cast iron cookware with dish soap and a nylon sponge (nothing abrasive). I towel it dry, stick it in the oven, set the temperature to 200 degrees, and leave it in there until it’s bone dry (just a few minutes). Then I take it out and lightly oil it with avocado oil, which is highly monounsaturated and won’t go rancid. Olive oil would work, too.
If you have burned on food that’s stuck really badly, boil water in the pan and it will loosen. I have a cast iron grill that got really badly caked with burned whatever and I got it loose without any scrubbing by boiling washing soda mixed with water. Washing soda is like baking soda, but stronger. It’s next to the clothes soap in the store.
I don’t know where people get the idea that washing with dish soap will remove seasoning. It’s very difficult to remove seasoning – you need oven cleaner with lye. Dish soap doesn’t harm the seasoning at all.
March 2, 2010, 9:46 pmMyra:
Sheryl,
I just stumbled on your site and am so fascinated with this post. I would love to try it. I just bought a Griswold from that looks very clean and smooth, although I see some minor marks (probably from cooking with a fork?). I want the completely smooth surface you have with your pan. Again the skillet is very clean. Do you think I need to strip with oven cleaner before re-seasoning using your method?
Thanks,
March 3, 2010, 10:03 pmMyra
Sheryl Canter:
Hi Myra. Seasoning won’t remove imperfections in the iron itself.
March 8, 2010, 11:37 amanatoliy:
Hi Sheryl,
Glad that I found this post before seasoning my cast iron. I followed your instructions starting from the “black rust cast iron seasoning” and my first coat with unrefined flax oil came out perfect. However after my second coat, there were patches, for lack of a better description, of dark yellow-extreamly sticky-goo. After scratching at it, much of the rim started to peel off.
I had preheated the pan, and it was completely dry before rubbing the oil onto it. I left the pan in the oven at 450 for an hour and let it cool for 2 hrs in the oven as per your instructions. I tried washing off the residue, and noticed that the pan smoked aggressively when placed on a burner to dry. Any ideas on where I went wrong?
March 8, 2010, 7:24 pmReid:
Hi Sheryl,
March 8, 2010, 7:32 pmI don’t mind the possibility of losing a $16 lodge skillet to a self cleaning oven over the mess of soaking with oven cleaner for days. Was wondering if, in your opinion, the water/vinegar and the black rust process would be necessary after the high heat?
Sheryl Canter:
> However after my second coat, there were patches, for lack of a better description, of dark yellow-extreamly sticky-goo. After scratching at it, much of the rim started to peel off.
You put the oil on too thick. That never works – you can’t speed up the process this way. It just forces you to start over. You have to use the thinest coats of oil possible. Wipe it on, then take a dry paper towel and wipe it off until the pan looks dry. There is still oil on it – it’s just a very thin coat. That’s how thin it needs to be for seasoning.
> Was wondering if, in your opinion, the water/vinegar and the black rust process would be necessary after the high heat?
Vinegar is only to remove heavy rust – too much rust to scrub off with steel wool cleaning pads. I don’t know if self-cleaning ovens remove rust. I never tried one. But if it’s a Lodge pan that’s got the original gunk on it, it’s probably not rusty so why would you need vinegar? Vinegar – even diluted 50/50 with water – can damage cast iron. You only use it as a last resort to remove significant rust. No rust, no vinegar! I only had to use the vinegar solution on one pan. The rest had little or no rust.
I recommend always heating the pan first before applying the oil. It helps the seasoning to adhere.
March 8, 2010, 9:12 pmJohn:
Very thorough analysis Sheryl, much appreciated.
I also noticed, like anatoliy mentioned, that my pan begins to smoke when placed on a hot burner. I typically like to get my pan nice and hot before searing a steak, and an not sure if I’m overheating it or if the pan is not meant to be used at high temperatures.
After keeping the pan on high heat, (maybe a 15-20seconds) I noticed that the colour on the bottom and the inside bottom turned a lightish grey colour, almost like the seasoning evaporated in patches.
I would very much appreciate any thoughts.
March 9, 2010, 1:38 pmGloria:
Sheryl,
I want to season a new carbon steel wok. I would like to do it in the oven. I am wondering if the same oil and technique will work as will the cast iron skillets? You said the iron in the pan helped to create the hard finish, is there another oil that works better on carbon steel?
Also i have several old cast iron skillets that I am using. Can I just start using some flaxseed oil on them? or do i need to strip them first?
And someone mentioned using Soy oil as it was high in the iodine test. You said it was semi-drying. I assume you are still using the flaxseed oil because it gives a superior finish?
March 21, 2010, 4:37 pmthank you,
Gloria
Dimitri:
Hi Sheryl:
I’m wondering how those 6+ layers of flaxseed oil will make any difference, if they’re going to be covered up anyway, over the natural course of time, with seasoning from the fat that will be cooked in the pan.
Ultimately, what’s the difference?
BTW, love your blog. I’m new to cast iron and have found it very informative.
April 19, 2010, 2:43 pmPaul:
Sheryl,
What a terrific blog! Thanks for doing this.
I have a question: I used your method on a fairly new (but not completely stripped; it had some patchy seasoning from minimal use ) browne-halcon skillet. Over several days I put 6 or 7 coats on. I have been using it for the last few days. Tonight, after making fajitas in it I noticed what looked like patches where the seasoning had worn off. Assuming I followed your directions accurately (big assumption), is this possible? Does the pan need to be stripped clean to season properly, or can one simply re-season right over existing?
April 21, 2010, 11:56 pmDimitri:
@Paul:
I’m not sure if Sheryl is still responding to these posts. Maybe she’s busy with other experiments. But I’ll take a stab at your question:
I think it’s important to strip the seasoning first.
It’s incredibly easy to do so, by putting your skillet (face down) into your oven, and running it through a clean cycle. Done!
You may also wish to put some good, thick aluminum foil on the bottom rack, to catch the old seasoning.
Some folks suggest putting the foil directly on the oven floor, but that risks having it melt (that’s what happened to me anyway).
Hope that helped.
April 24, 2010, 12:06 pmD
cal:
Dear sheryl,
I bought a brand new oval cast iron hibachi griller which i suspect is not pre seasoned. The whole construction is black but doesn’t look as shiny or glossy as the Lodge logic hibachis (preseasoned, much more expensive than mine). It is also rough to the touch. What are my options? should i sand it down until all the black coating is off and then season it myself? or should i just give it a quick wash and just season on top of the already present black coating?
April 27, 2010, 2:55 amSheryl Canter:
Some quick responses (true I’ve been pretty busy lately)…
> I also noticed, like anatoliy mentioned, that my pan begins to smoke when placed on a hot burner. I typically like to get my pan nice and hot before searing a steak, and an not sure if I’m overheating it or if the pan is not meant to be used at high temperatures.
I don’t know what’s happening to your seasoning. I do know that you don’t need to heat cast iron to a very high temp – sounds like you are overheating the pan. Cast iron holds heat very well – you don’t have to use very high heat. Also, are you aware that burned meat is carcinogenic?
Re another comment… I always strip pans before seasoning. Who knows what’s on there – better to get it off and start clean.
May 3, 2010, 6:40 pmDave:
This is a great post. Assuming I seasoned using your method, how often do you think you would need to reseason?
May 5, 2010, 4:39 pmMycroft:
Safflower (not sunflower) oil works equally well. It’s available in many grocery stores, and dries fairly aggressively. I’ve been using (and recommending) it for years, for exactly the same reason.
May 6, 2010, 12:54 pmMycroft:
I should add: there is now some safflower oil in the market that’s been modified to not dry. I use Hollywood brand, which is widely available in the Boston area. If the oil tends to gum up around the cap, that’s the good stuff. (Note: It will also do that on your clothing. Wash out any oil spots immediately, or you will never get them out.)
May 6, 2010, 1:42 pmRussell:
Hi Sheryl, Just saying THANK YOU, I did waste alot of time reading all the crap info on the internet until I found your site. You have good solid information that is logical and tested. I think the most common misleading information on seasoning is “turn the pan upside down so all the grease can drip out.” But you’ve definitely cleared that up.
May 7, 2010, 9:52 pmHerman:
Hi.
Im not sure why you regard linseed oil as not edible.
May 13, 2010, 3:53 amHere in Germany, at least in some northerly regions of, it is totally common to eat linseed oil on top of potatoes with cottage cheese. You will see linseed oil being sold right next to olive or corn oil in the grocery store.
It has a very distinctive taste, and you will certainly not use large quantities, but so far nobody seems to have had any ill effects from digesting linseed oil to my knowledge.
The small amounts transferred from the pan to your food will be neglectible.
In general, people should be more concerned about what is _already_ in their food, rather than getting mildly paranoid about leftover detergents or aluminium spoons or something.
Sheryl Canter:
There seems to be some confusion here.
Unrefined oil from flax seed – not edible – is called linseed oil. Don’t use this to season pans. Use the high quality edible version, called flaxseed oil. It’s available in health food stores.
If you eat it, don’t heat it. The polymerization that makes flax seed oil so effective for cast iron seasoning is not something you want to occur inside your body. That’s carcinogenic.
May 13, 2010, 10:15 amPhaedrus:
A million times thank you. Thank you for FINALLY cutting through all the anecdotal GARBAGE surrounding this topic. Thank you for being intelligent enough to step back and evaluate it with a scientific, skeptical and analytical mind. Thank you for figuring this out from the ground up. Thank you for not simply writing a somewhat twisted and half-hearted ‘what worked for me’. And most of all, thank you for allowing us to read it, and benefit from it. I have been trying in vain to figure this out for years, and this is the answer I’ve been looking for. THANK YOU!
May 17, 2010, 4:04 pmSheryl Canter:
Thank you for your thank you! I’m very glad that others find my research useful.
May 17, 2010, 4:17 pmLinda:
Yours is not the only site to promote the use of oven cleaner (lye) to remove the old seasoning on cast iron. I am troubled, however, as my soap-making book makes clear that ANY utensil which has touched lye is no longer to be used for food. Would lye not be trapped by the pores of the iron? Would the new seasoning sufficiently seal in the lye? Sounds scary…
May 19, 2010, 11:56 amDimitri:
@Russell
Using your oven’s cleaning cycle (and turning your pans upside down, to catch some of the old seasoning, as it flakes off) is the safest and easiest way to strip old seasoning. It’s not “misleading”. It works. Using lye and oven cleaner is not necessary, and downright dangerous.
That said, using 7 layers of flaxseed oil (after I stripped the old seasoning from my pans) was amazing! The new seasoning is superb.
May 19, 2010, 5:31 pmSheryl Canter:
Some of us (for instance me) don’t have ovens with a self-cleaning cycle. Also, there is a risk of warping the pan when you use extremely high heat. A self-clean cycle reaches temperatures of 900-950 degrees F – hot enough to soften the iron.
Lye (as a bath or sprayed on as oven cleaner) isn’t toxic – despite what somebody may have written in a book. It rinses off completely. You do need to handle it carefully. Wear gloves and goggles – it’s not a joke.
The best way to clean is electrolysis, but I have no way to do that, living in a small NYC apartment. You need space and ventilation for that, and a lot of equipment. So I use oven cleaner and it works fine.
I talk about the cleaning issue more in my previous post:
http://sherylcanter.com/wordpress/2010/01/perfect-popovers-and-how-to-clean-reseason-cast-iron/
May 19, 2010, 5:56 pmRussell:
@Dimitri – Thanks for nothing
You clearly did not read my comment. I was talking about seasoning a pan. And you are talking about the exact opposite – stripping the seasoning
May 20, 2010, 11:46 amI said “misleading information on seasoning”
Kevin:
Great article, I have read on other places of the internet that claim that Carbon is the substance that stops sticking. To my line of thinking polymerization is a more likely. Possibly a combination of both.
It’s been a couple of months since you’ve posted. Has the flaxseed oil worked out as hoped? I can’t see stripping a pan unless there was a good reason.
I have been very happy with my skillet but I recently cooked up some fajitas and now everything sticks. It’s not the first time something like this has happened. I’m on my second run through in the oven with some canola oil. I’m certain this will fix it for a while but I’m wondering if flaxseed would be more permanent.
How thick does the flaxseed build up? You said that you used 6 coatings. Did that seem right for you?
May 22, 2010, 12:50 amSheryl Canter:
The pans I’ve seasoned with flaxseed oil are great. I use the muffin pan pictured above all the time, and the muffins slide right out. I’ve had problems with muffin pans seasoned in other ways, so this is great.
The seasoning doesn’t get literally “thick”. When you put it on thick enough to be detectable, it tends to come off – which may be the problem you’re having. After 6 very thin coats, the pan starts to develop a slight sheen. That’s when I figure it’s done.
May 22, 2010, 7:08 amKevin:
I have done the seasoning thick but that ends up pealing or speckling off. I’m pretty sure last night when I used EVOO I made it to thick. Eggs did wonderful this morning but I’m sure I’ll start seeing pieces come off in a month or so. Depending on my use. Canola oil doesn’t go on thick but it doesn’t seem to last. My Initial seasoning with was last year when I used lard. I’ve probably did a mild re seasoning about 4x since I’ve had the pan. One thing you got to love about cast iron. Even if you do mess up the cooking surface, you can still fix the pan. When I get used to it cooking well, I can’t tolerate having it preform poorly.
I’m surprised my favorite way to clean cast iron isn’t posted yet. I use the high intensity burner on my grill. 1 hour of that and it’s cover with ash.
May 22, 2010, 8:58 amSkillet:
Hi Sheryl,
May 22, 2010, 6:01 pmYour blog has been very helpful. I recently cleaned and derusted 2 cast iron pans using your techniques. I did my first seasoning with flaxseed oil that I bought from Whole Foods. Expiration date 12/10. The oil has a fishy smell. Is this normal, or does it mean it’s rancid? It doesn’t smell “skunky”, just fishy. I’m assuming it’s not normal, or you would have mentioned this in your post.
Thanks for your help!
Sheryl Canter:
Flaxseed oil has a smell, but I’m not sure I’d describe it as “fishy”. It does go rancid very easily – that’s why it’s the ideal oil for seasoning cast iron. Chemically, the seasoning process is the same process as “going rancid” – the release of free radicals. If the oil is rancid, it’s still fine to use for seasoning, but DO NOT EAT IT.
May 22, 2010, 8:51 pmTodd:
I have a newer lodge skillet. (2 months old) would it still be necessary to use lye and strip it? Or could I begin the process of seasoning it with flax oil?
May 24, 2010, 11:46 pmSheryl Canter:
Lodge skillets come “preseasoned” with a waxy coating. It makes no sense to season on top of that. If you don’t like the idea of the waxy coating, strip it down. Most people just use it. The quality of the cast iron isn’t as high as antique cast iron such as Griswold. It’s bumpy rather than smooth. You’ll never get the glassy finish.
May 25, 2010, 10:39 amBC:
Hi Sheryl!
Love these articles. I just inherited my dad’s old cast iron- one deep skillet, one shallow, and a large Dutch Oven. I’ve seasoned them with sunflower oil after heavy scrubbing (they were in storage for 10+ years). They came out black and pretty shiny. The next time I reseason them, I’ll definitely try out the flaxseed oil, I already know where it is in the supermarket!
May 27, 2010, 9:02 pmSheryl Canter:
Hi BC. I expect that sunflower oil is also very good for seasoning because, like flaxseed oil, it’s very high in polyunsaturated fatty acids and goes rancid (the “seasoning” effect) at relatively low temperatures. You can’t safely use sunflower oil in cooking. That makes it a good seasoning oil.
May 27, 2010, 9:05 pmBC:
That’s great! I haven’t actually used the pots yet, though. I’m actually tempted to just burn the seasoning I have on there and restart with a flaxseed seasoning.
Do you have any recommendations on what kind of spatulas to use with cast iron? Some say to use steel to even everything out, but others say to use plastic so as to not scratch the seasoning.
May 27, 2010, 9:55 pmSheryl Canter:
I use plastic (or silicone or wood) so as not to scratch off the seasoning. I tried the metal spatula advice, and I had to reseason the pan.
May 27, 2010, 10:14 pmsnaxalotl:
great article – glad to see people seriously interested in seasoning rather than blindly following whatever traditional advice. I’ve always been most bothered by instructions to season by filling the pan with oil
just to clarify a couple of things: lye is caustic but non toxic; it’s not the fact it washes off easily, but that the components of ionic compounds can generally be considered independently (eg a solution of NaCl and KI is identical to a solution of KCl and NaI). lye – NaOH – comprises the sodium you find in table salt and the hydroxide found in (the small dissociated proportion of) water. second, the problem with hardware store linseed oil isn’t that it’s unrefined, but that it contains “dryers” … metallic salts that speed up polymerization at room temperature. this oil is often, misleadingly, called “boiled” linseed oil. this is easily confused with “stand oil” – linseed oil that has been held at high temperature in oxygen free conditions. stand oil is used by artists and in high-end violin varnish etc. because it not only dries quickly but also gives the toughest outcome of the linseed products; and since it doesn’t contain dryers it could very possibly be safe and effective for seasoning (i’ll leave it to others to do that research)
couple of other thoughts: (a) tung oil is apparently tougher than linseed oil as a wood finish. i believe candle nuts are very closely related to tung, so next time i season a pan i’ll probably rub one of these very oily nuts against the hot surface. (b) I once poured a sizeable layer of oil in a pan and heated it for ages just for the heck of it, and i got a very (~1/8 inch) thick layer that was very hard and slippery and didn’t have any tendency to chip off (can’t remember which oil i used). (c) in addition to polymerization, it seems to me an important aspect of seasoning is that any components that can’t cope with the heat will vaporize off, giving a process of survival of the fittest (= most polymerized). (d) the reason i don’t like cleaning a seasoned pan with detergent is that i like to leave a slightly greasy surface after cleaning so i can dry the pan off on the stovetop and slightly re-season it
May 28, 2010, 10:27 amLarry:
What a great article. I’ve got a couple of oldish cast iron pans with patchy/sticky seasoning, so I’m going to give stripping and re-seasoning with flaxseed oil a try.
Upthread, someone asked about using this method to season carbon steel pans, but nobody seems to have answered. I’m no chemist, and I’ve got a CS paella pan that needs seasoning before I use it. Any idea as to whether this technique will work for me?
May 28, 2010, 1:20 pmRussell:
Anyone want that glossy finish and not smoke up your house?
This is how I did it. You can use whatever oils you want.(Flax, sunflower, soy, canola…)
1. I used canola and wiped it on thin
June 7, 2010, 12:55 pm2. Then you want to dry the oil by cooking below the smoke temperature at first. Canola smokes pretty hot at about 475F, so bake your pan at 350F for 1.5 – 2 hours, it will not all disappear in the form of smoke. Instead it will be slightly tacky.
3. This is where you follow the high heat advice and crank the temperature beyond the smoke point of the oil you’re using 475F-500F for canola for 1 hour. That bakes the dried oil on the pan and really does feel like smooth enamel and will no longer be tacky.
4. So it’s a combination of peoples advice that is the actual way to season a pan. Found out from experimentation. This also saves money on oil because it doesn’t all turn to smoke. Even when I baked on the tacky oil past smoke point at 500F it wasn’t that smokey in here. Didn’t even use my fan. Cool and repeat
Good luck
Carry:
First of all, I am far from scientifically minded. Most of what you discuss is over my head, I just don’t analyze the same way you can
I’m in the massage therapy business so when I saw that you have used avocado oil, I was intrigued. Brought a bottle home from the warehouse today, because I have been stripping off the pre-seasoning of a 12″ Lodge. Was hoping to smooth it out a bit, but reading the comments discussing that it will always be a rough surface I am a little disappointed.
One thing that was driving me absolutely batty was the rust. I left the skillet inside a bag after spraying the heck out of it with Easy Off the day before. Obviously it was slimy with gunk when I took it out. Tried to rinse it well in the sink, and used a 0000 steel wool to try and get any last black bits off. No sooner did I try and dry it than it would rust over. I tried and tried to get it off, wipe it down, wrecked some bar towels, shredded paper towels. Eventually tried to subdue the rust with a swipe of vinegar/water solution, which held it off a little, so i put it in my oven that was at 250 degrees to dry out. Took it out and swiped it with a thin layer of avocado. Looked fantastic right there, popped it back in and cracked the heat to 500, left it there for about 45 minutes.
Of course the entire time I was second guessing the steps I took. Should I have used anti-bacterial soap when rinsing off the oven cleaner? Should I have not bothered with the steel wool at all, which did get a little wet in the process? Should I just have done what other people have done with theirs – build a campfire and toss it on the coals?
Please let me know if you think I made any grievous errors. Right now the pan is still cooling slowly in the oven (second floor apartment, it’s so hot already I can’t leave the oven open a crack to cool faster).
Thanks so much for your blog, I am hoping to make the popovers someday when the Fat Man in the Red Suit brings me something to make them in
June 11, 2010, 9:23 pmSteve:
Sheryl,
Have you ever seasoned a stainless steel pan with a similar process? Right now my eggs stick like crazy and I am thinking of using this process to help.
June 20, 2010, 3:17 pmSheryl Canter:
Steve – you cannot season stainless steel the way you can cast iron. It’s a completely different thing. There are techniques for cooking with stainless steel to prevent sticking. I can’t tell you what they are because I never liked it either and chose cast iron instead.
June 20, 2010, 8:10 pmSteve:
Sheryl – Thank you for the reply! I am still considering seasoning for an egg pan I use because my grandfather swore by his seasoned egg pans. I was never able to get the entire process out of him, and not sure he even remembered the details. But I’ve used the pans and they are great! I’ll let you know how it goes if you are interested. Also, thanks for the great article!
June 21, 2010, 9:50 amKingsthorpeDavid:
Sheryl this is fascinating and the best information I have ever sourced on seasoning cast iron. I now have my bottle of New Zealand organic cold pressed Flax seed oil and ready to start! And yes it was in the refrigerated section in the store!
June 22, 2010, 3:37 amI am a cast iron Camp Oven collector and cook in Queensland Australia.
Your dedication is really appreciated.
Tom Murphy:
Since hemp seed oil is a drying oil, which used to be used in the manufacture of paints, would it be good to use to season cast iron as well? I have a lot of Griswold cast iron pans that I could try this on.
June 26, 2010, 7:59 amTed:
Sheryl, Thanks soooo much for all your work and expierments here. I love cast iron and have been trying your methods for the past couple of weeks. I seasoned my pan with the flaxssed oil as mentioned, and everything came out looking good. Used it a couple of times and worked great. Then I was making a recipie that called for italian dressing. After finishing dinner and looking at the pan, it looked as if all the “seasoning” had been washed away???? Was this do to the vinager in the dressing??? I have also boiled water in the pan for making other dishes and it seems the “seasoning” gets washed away again. Are there things you should not cook in a seasoned cast iron pan that will ruin, or deteriorate a well seasoned pan?? Would love to hear your thoughts.
Thanks!!!
July 6, 2010, 3:01 pmSheryl Canter:
Hi Ted. You did manage to find the two great no-nos of cast iron cooking: boiling water and cooking acid-based foods (like tomato sauce or anything with a lot of vinegar). Both can actually damage the iron, as well as the seasoning. People soak in vinegar to remove rust, but if you do it too long you can destroy the pan (see my popover post).
I use a ceramic pot when I need to boil water or cook something highly acidic.
July 6, 2010, 5:40 pmScott:
Sheryl, what would your second recommendation be for a good oil if I’m not going to use flaxseed oil? Canola or soybean, or something else?
Thanks.
July 9, 2010, 6:40 pmMatt:
WOW! There are some fantastic tips and tricks here. Thanks both to Sheryl and everyone else for posting! Seasoning cast iron cookware seems to me akin to fishing; everyone has a different technique but none of them work for me. I have a dutch oven and a double sided griddle that I have “seasoned” with Crisco by various methods. It began with seasoning in the oven but my wife ran me out of the kitchen after I smoked up the house. Next, I moved my operation outside to the grill but my seasoning came out splotchy with some tacky spots. I was convinced that it was because I couldn’t keep the coals going long enough to finish the seasoning process. The only logical thing to do in my mind was to do the same thing over a campfire. I heated my cast iron and took a rag full of Crisco and wiped all surfaces repeatedly. The Crisco immediately smoked because I was putting it on a surface that was already screaming hot. After letting it cool, it seemed to be seasoned pretty well so I tried to cook in it but it seemed like the seasoning broke down a little and wasn’t smooth and uniform. I was pretty frustrated and discouraged that I would never get the smooth, seemingly indestructible surface that my grandmother’s cast iron cookware had. I chalked it up to repeated use and I figured that I would eventually have a good seasoning. Flash forward to this last weekend. I was grilling some food and on one side of my grill I had my griddle heating to cook some bacon on the flat side and my dutch oven heating up empty next to it. After all, this was the kind of use that provides the seasoning I was looking for, right? After the bacon was cooked, I took the grease from the griddle and smeared the dutch oven down with it. I wiped both pieces down until they were lightly coated and turned both upside down to prevent any pooling. I let them both sit over the hot coals for about 2 hours until the coals went out and the pieces cooled enough to touch. I rinsed them under hot water and wiped them out. The first thing I noticed was that the griddle had a line across it where the seasoning was worn off but the dutch oven had a very metallic looking glaze all over it that doesn’t wipe off. The inside looks great but the outside has patched of carbon(?) and a light rust spot on the bottom. Can anyone explian what happened to these pieces? Do I have to totally strip and reseason both of them? I am hoping that I can just hit these spots with a little steel wool to sooth them / knock the rust out and try the flaxseed oil method that Sheryl outlines. I want the seasoning like the pictures she has above! Also, I do cook over campfires / grills quite a bit so I need everything to be able to handle heat very well. Thanks for reading…any advice is welcomed.
July 12, 2010, 4:58 pmTim:
Thanks for a very interesting post. The one thing that it left me curious about at the end is – what is the polymer created, and is it as OK for health as the oil it is created with? I will do some further reading.
July 13, 2010, 11:29 amTyler:
Hey, great guide, glad to see someone giving a thorough explanation about the whole thing. My pan is currently baking through its 3rd coat, and the first two have gone great. I plan to make a youtube video once it’s all done showing the results and directing people here to give due credit! I’m wondering how you think soap will affect this coating. I’d have to imagine it wouldn’t hurt – in fact, I doubt you’d be able to get this coat off with anything but the cleaning methods you mentioned in the other post. Still, wondering what you think. Thanks again.
July 16, 2010, 8:51 pmJack:
http://sherylcanter.com/wordpress/2010/02/black-rust-and-cast-iron-seasoning/#comment-496
July 20, 2010, 8:01 pm