cast iron: polymerizing oils and a better seasoning

From a different thread, I wrote the following:

Linseed (flax) oil is kinda famous for becoming rancid quickly.  And, so, you're saying that it is also indicative that it is quick to polymerize.

Grape seed oil has a similar reputation.

So it seems there is at least a mild challenge of getting the oil from the plant into the bottle and from the bottle into my pan.  Just simple storage can be tricky.  ??

So, at cooking temperatures, any oil will polymerize, right?  And then it doesn't really matter which one does it at the lowest temperature, but which one will do it more evenly and result in a slipperier surface.

In fact, we might end up with different fats that polymerize in different ways.  Some might leave a super slippery surface, but be poor for the first layers on iron.  Some might help fill in a pit or fill in a rough (new lodge) surface.

I know that I have had times where fats will leave a polymerized layer that is a thin, contiguous layer.  And other times where fats will leave a layer that is "mottled" or "spider-web-ish".  I suspect that there are a lot of factors here, one of which could be the different types of oils.  It might even be compounded with the type of oil/layer from the previous use of the pan.

I guess my point is that it is results that count.  And the real results would be to try a dozen different types of fat cooking the same thing five times in a row and to conclude which was the best on the fifth time.

First, I am seeking validation that while linseed (flax) oil may be good for .... uh .... painting/staining a piece of furniture because that piece of furniture will not be exposed to high temps, that it doesn't necessarily make it a great candidate for seasoning cast iron.  Can I get agreement on that?  Is my thinking sound?

Next, I think it may be wise to caution people against the use of linseed oil because I think it might have chemicals added - even if the label says it does not have chemicals added.  Refrigerated flax seed in a dark bottle might be a much better choice.

And finally ....  and this, I think, is the most important thing:  what might be the combination of oil of temp to get a hard contiguous layer of polymerized oil as opposed to the "mottled" or "webby" layer that I usually see in a secondary seasoning layer?

And while we're on the subject .... I would really like to better understand the free radical stuff. 

Of course you want to use food-grade flaxseed oil (from a health food store), not the linseed oil that a hardware store sells.

I've only seen the "webby" thing when I used bacon fat, and I think that happened because there are non-oil things in it - salt, notably, and who knows what else.

"Free radicals" have to do with molecular chemistry - unstable molecules emitting electrons until they are stable. It's a chemical reaction that causes the molecule to change into something else.

Paul, after reading/following your cast iron thread I was still using a sticking cast iron skillet, I don't know what I was doing different than others, but I tried everything.

I followed the link you posted to Sheryl's Blog - The article titles are at the end of these URL's
http://sherylcanter.com/wordpress/2010/01/a-science-based-technique-for-seasoning-cast-iron/
http://sherylcanter.com/wordpress/2010/02/black-rust-and-cast-iron-seasoning/

I followed her directions and now have the nicest, slick black finish on my pans ever!  They look better than they did when purchased, and we are making pancakes again for the first time in years.... I'm a happy camper to say the least.

I used the health store flax seed oil - it works great.  I do not see why you are having trouble excepting it's use for this purpose.  I now love cooking with my cast iron, but most important I'm not afraid to use it, I know I can easily re-season it should the need ever pop up again.

By the way that's coconut oil in the jar next to the pan, we don't use flax seed oil for cooking just seasoning.

That is awesome to hear. Thank you for posting this! (I'm Sheryl.)

Your most welcome Sheryl

~Jami

Sheryl,

Perhaps the point is that the flax oil will polymerize before the smoke point?  Or, maybe the polymerization would happen without the webbiness? 

But then it would seem that the corollary would be that you would want to not use flax oil for general cooking - because then you would be eating a lot of polymerized oils. ??

You don't want to use flax oil for cooking; you want to eat it raw. At least that's what I've always heard--and the folks I know who are serious about their flax keep it in the refrigerator, or even in the freezer. I gathered from that blog post (REALLY informative, btw, thanks Jami and Sheryl!) that the smoke point for flax IS the polymerization point, so you most certainly do not want to heat it very much, if at all.

I'm going to try stripping mine and replacing the seasoning with flax oil sometime next week; I'll report back on how it works.

Exactly Kerrick    you've got it!

Buy the way, those pancakes are from the Nourishing Traditions Cook Book and use wheat flour soaked in liquid yogurt overnight before cooking the next day - boy were they goooood!

You never ever never want to use flax oil for cooking. Polymerization is for the pan, not for inside your body. Free radicals inside your body are known to be carcinogenic. The smoke point is the point at which the free radicals are released. Flaxseed oil has a very low smoke point. Never cook with it, and keep it in the refrigerator.

Sheryl,

Is this smoke-point free-radicals thing true for all oils?

And if so is there are chart showing the smoke point temps for various oils?

Thanks

from http://www.cookingforengineers.com/
Fat                              Smoke Point     °F           °C Unrefined canola oil                          225°F 107°C Unrefined flaxseed oil                     225°F 107°C Unrefined safflower oil                  225°F 107°C Unrefined sunflower oil                     225°F 107°C Unrefined corn oil                             320°F 160°C Unrefined high-oleic sunflower oil 320°F 160°C Extra virgin olive oil                          320°F 160°C Unrefined peanut oil                  320°F 160°C Semirefined safflower oil                  320°F 160°C Unrefined soy oil                          320°F 160°C Unrefined walnut oil                          320°F 160°C Hemp seed oil                                  330°F 165°C Butter                                          350°F 177°C Semirefined canola oil                  350°F 177°C Coconut oil                                  350°F 177°C Unrefined sesame oil                  350°F 177°C Semirefined soy oil                          350°F 177°C Vegetable shortening                  360°F 182°C Lard                                                  370°F 182°C Macadamia nut oil                          390°F 199°C Refined canola oil                          400°F 204°C Semirefined walnut oil                  400°F 204°C High quality (low acidity) extra virgin olive oil 405°F 207°C Sesame oil                                  410°F 210°C Cottonseed oil                                  420°F 216°C Grapeseed oil                                  420°F 216°C Virgin olive oil                                  420°F 216°C Almond oil                                  420°F 216°C Hazelnut oil                                  430°F 221°C Peanut oil                                          440°F 227°C Sunflower oil                                  440°F 227°C Refined corn oil                          450°F 232°C Refined high-oleic sunflower oil 450°F 232°C Refined peanut oil                          450°F 232°C Refined Safflower oil                  450°F 232°C Semirefined sesame oil                  450°F 232°C Refined soy oil                                  450°F 232°C Semirefined sunflower oil                  450°F 232°C Olive pomace oil                          460°F 238°C Extra light olive oit                          468°F 242°C Soybean oil                                  495°F 257°C Safflower oil                                  510°F 266°C Avocado oil                                  520°F 271°C
There is also a chart on wikipedia

Thanks for posting the chart, Ken. That's where I found it, too.

Yes, Jami, the smoke point for any oil is when it starts to release free radicals. That's why you never should heat oil for cooking so hot that it smokes, and if you do it by accident you should throw it away (unless you're seasoning a cast iron pan, of course).

The reason this chart was posted on Cooking for Engineers is so people would know which oils were safe for cooking and which were not. Here's the beginning of that article:

http://www.cookingforengineers.com/article/50/Smoke-Points-of-Various-Fats

The smoke point of various fats is important to note because a fat is no longer good for consumption after it has exceeded its smoke point and has begun to break down. Once a fat starts to smoke, it usually will emit a harsh smell and fill the air with smoke. In addition it is believed that fats that have gone past their smoke points contain a large quantity of free radicals which contibute to risk of cancer.

https://permies.com/permaculture-forums/3496_0/cooking-and-food-preservation/black-residue-on-cast-iron-skillet

I was so inspired by Pauls article on cleaning cast iron pans that I spent most of the day cleaning up my old iron Ive collected over the years.  I posted at the link.

I have been using a spray can of canola oil (PAM) which I just happened to have on hand, with coarse salt after the pan is heated and scraped down.

According to Ken's chart refined canola oil should have a smoke point of 400 degrees F.  The method I am using heat + scraping or wire brushing, and then a final rub down with just a spritz of oil on a paper towel with salt means that with each use the old oil is replaced with fresh oil so carcinogens should never form.  You could use lard the same way -- just a dab of fresh lard after each use.

I'm trying to eliminate all soy oil and canola oil from my diet.  But, that's just me.  The mention of canola oil made me think of mentioning that.

Why? Why eliminate soy and canola oils?  I used canola oil thinking it had a higher smoking point -- and I had some on hand because I was using it to remove rust from my tools.  It comes in a spray can just like WD40 (!)

According to the chart olive oil - which I more normally have in my kitchen has a higher smoking point.  I guess peanut oil would be a better frying oil.

I have just seasoned three Griswolds and an unknown no. 12 using flaxseed oil, and now have four beautiful skillets eager to be used.

However, because of a severe headache during the seasoning process, I began to wonder about the health risks associated with cooking on a flaxseed glaze. I read that flaxseed oil must not be used for cooking. If any of the seasoning layer comes off in using the pan, isn't that adding cooked flaxseed oil to our food? Maybe the polymerization process eliminated any of the harmful agents (free radicals).

Will my pans smoke when I put them onto the fire (I'll find that out soon enough!). If they initially smoke, will that diminish in time?

In seasoning, I ran my oven temperature as high as 550 degrees and held them over 400 for an hour. With four cast iron pans in the oven, it held heat for about three hours before the pans were cool enough to handle. Because of this health question I stopped the process after the fifth baking cycle. I started by sand blasting down to bare metal and re-polishing the inside with a wire wheel. They are a beautiful deep, dark coppery color.

Any smoking oil will give you a headache. You need very good ventilization when you do this. Once the polymerization is complete, the surface won't smoke.

This is a great post because I believe it identifies the real issue to heart/cardiovascular issues not cholesterol. I use a cast iron pan and it is awesome, I will have to learn more about the polymerizing of the pan, this is new to me.

Jocelyn shows us how to put a new seasoning layer on a funky old

Nice video, and great info!

Am I the only person to use bacon grease?  It never smokes at the temperatures I use, and it's absolutely free because I've already bought the bacon!  And the delicious bacon flavor... mmmm.

Well, there's a health issue, I'm sure someone will say... my grandma used bacon grease all her life, and it killed her early, at the tender young age of 96. 

Veg and seed oils frighten me a bit, considering there's no way of knowing where they come from.  Then stuff in spray cans... seriously?  That's creepy, not to mention a waste of resources in the form of that can you throw away.  What if you accidentally grab the Liquid Wrench, cooking breakfast some dark morning? 

Lard and bacon fat are our staples. Occasionaly we use some coconut oil too.

Personally, I've eliminated all oils that have a GMO equivalent in the marketplace.  The cross contamination has made even organic foods "iffy".  Even organic farmers can't promise that you aren't getting GMO content in their foods. 

Mainly for health and partly because it seems like a protest or a boycott.  I consider GMO foods to be the bane of all life on this planet and the first and most important evil on my list of things to concentrate on changing.

I really hope that everyone will look into this issue and determine for themselves if I'm crazy or not

wombat wrote:
Why? Why eliminate soy and canola oils?   I used canola oil thinking it had a higher smoking point -- and I had some on hand because I was using it to remove rust from my tools.  It comes in a spray can just like WD40 (!)

According to the chart olive oil - which I more normally have in my kitchen has a higher smoking point.  I guess peanut oil would be a better frying oil.

Grassfed beef tallow is my staple pan seasoner.  It seems to make a bulletproof nonstick coating that lasts a good long time.

On the soybean oil issue, I eliminated it from my repertoire as well, primarily because of the horrible extraction process required to get the oil out of the seed (involves hexane, high temperatures, alkaline washes, and various other industrial processes that I don't want to eat).  Also, the omega-3/6 balance is way out of whack, which is believed by many to be a factor in various "diseases of civilization."

It costs a lot more, but I try to stick to extra-virgin oils or animal fats that I render myself from animals I know were raised in conditions they are adapted to.  I think that once you get past the virgin oil level, many of the vegetable oils have been processed with crazy chemicals, and undergone oxidizing transformations that may contribute to atherosclerosis.

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

Chemistry of Cast Iron Seasoning: A Science-Based How-To
January 28, 2010, 6:31 pm
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.


http://sherylcanter.com/wordpress/2010/01/a-science-based-technique-for-seasoning-cast-iron/?roostBDI=375678

Craig Storms wrote:Chemistry of Cast Iron Seasoning: A Science-Based How-To
Chemistry of Cast Iron Seasoning: A Science-Based How-To
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.
http://sherylcanter.com/wordpress/2010/01/a-science-based-technique-for-seasoning-cast-iron/?roostBDI=375678

A lot of people quote from and link to this article from Sheryl, but I have never seen Sheryl post anything scientific about how she came up with her method other than mentioning the keyword of polymerization. I think that cast iron seasoning might have more to it chemistry-wise than just a polymerization of oils. I have posted my thoughts at http://www.reddit.com/r/askscience/comments/12c42u/what_is_cast_iron_seasoning_really_made_of/

Basically, I think that cast iron seasoning might be a combination of a polymerized layer working together with oils that have saponificated (turned to soap) and/or soap that has mixed with oil to become grease. Paul's long post on richsoil.org about how to use cast iron without worrying about it too much along with using a straight edged stainless steel spatula / pancake flipper are what got me thinking about this theory.

Folks the key is the formation of cross-linked bonds.
Drying oils like flax seed and walnut were used in art because they formed a hard surface when dried.
This was due to their ability to form cross-links.
You do NOT have to take a oil to its smoking point for it to form cross-links.
You can stay under the smoking point and allow for more time while applying thin layers one at a time.
One key before you start is to strip all the oil off the pan and start with a clean surface so the cross-links can bond to the surface of the pan.
I de-oil my pans before seasoning. I then wash and put in oven at 350. Once it is hot and dry I apply thin layers of flax seed oil and back at 350.
I will back a hour or two and then apply another thin layer of oil. Than after all layers are baked I turn off oven and let it cool.

I have a Wagner that had been sitting in a drawer for a couple years that I pulled out and cleaned off using Sheryl's tips- no self cleaning oven, so I sprayed oven cleaner over it and tossed in a plastic bag to sit for a day. I cleaned that off the next day, wiped off a tiny bit of rust that started after the coating was gone, and then coated it all with the organic, food grade flax oil I bought for this. Wiped it down and tossed into the oven at 450 or so for an hour, then let it cool and repeated 5 more times. After it cooled off the surface was smooth and not tacky at all.

Looked great afterwards, I put some olive oil in the pan and heated it up on low/medium heat (4 of 10 gas heat) and once it heated up I tossed an egg on to cook. It stuck quite a bit, and I saw numerous little bits of coating flaked off. I was using the metal spatula Paul recommended in his article but wasn't scraping hard. After I was done it took some work to clean the surface and a lot more little flakes came off, and almost all of them were around the middle, which is where the flame was sitting when on low.

Not sure if even low heat was enough to soften the surface here, but this was far less effective than the first time I seasoned the pan, which I think was with canola oil around 5 years ago. Not sure if I can scrub the surface down until no more flakes come off, then toss back in the oven to add more coats, or if I need to use the Easy Off again and get it back to bare metal, and then try it again using Alex's idea of heating it to 350 and applying coats that way. I notice the chart shows the smoke point of flax is 225, so aren't we hitting that smoke point anyways if we season at 350? Maybe just not as bad as 450-500?

Mark Tudor wrote:I have a Wagner that had been sitting in a drawer for a couple years that I pulled out and cleaned off using Sheryl's tips- no self cleaning oven, so I sprayed oven cleaner over it and tossed in a plastic bag to sit for a day. I cleaned that off the next day, wiped off a tiny bit of rust that started after the coating was gone, and then coated it all with the organic, food grade flax oil I bought for this. Wiped it down and tossed into the oven at 450 or so for an hour, then let it cool and repeated 5 more times. After it cooled off the surface was smooth and not tacky at all.

Looked great afterwards, I put some olive oil in the pan and heated it up on low/medium heat (4 of 10 gas heat) and once it heated up I tossed an egg on to cook. It stuck quite a bit, and I saw numerous little bits of coating flaked off. I was using the metal spatula Paul recommended in his article but wasn't scraping hard. After I was done it took some work to clean the surface and a lot more little flakes came off, and almost all of them were around the middle, which is where the flame was sitting when on low.

Not sure if even low heat was enough to soften the surface here, but this was far less effective than the first time I seasoned the pan, which I think was with canola oil around 5 years ago. Not sure if I can scrub the surface down until no more flakes come off, then toss back in the oven to add more coats, or if I need to use the Easy Off again and get it back to bare metal, and then try it again using Alex's idea of heating it to 350 and applying coats that way. I notice the chart shows the smoke point of flax is 225, so aren't we hitting that smoke point anyways if we season at 350? Maybe just not as bad as 450-500?

I had the exact same problem with flax seed oil. I've read somewhere on the internet that flax seed is great for a decorative display seasoning for cast iron, but it flakes off in real world use. When mine flaked off I did as you described(scrape/scrub off the rest of the flax seed that is willing to come off) then season with another oil(canola/vegetable/lard) that doesn't end up flaking like flax seed.

I recently used flaxseed oil to season a brand new cast iron pan and had great results! I got a 12" Ozark Trail pan as a gift and the cooking surface was pretty rough from the casting process. I spent maybe 10 minutes with some 180 grit sandpaper smoothing it out and removing the worst parts while also removing the factory seasoning. I then wiped it out and cleaned it by using flaxseed oil and changing cloths until it wiped clean. I sort of followed the links mentioned above but with one important difference - I cooked in my oven and used the hot oven to season the pan. Instead of doing it all at once I only ran the oven an extra hour a day. It doesn't get cold here in Florida that much, so it made sense for me to make use of the heat to make dinner, heat the house a bit, and season my pan. I did 2 coats a day for 4 days and it looked really nice to me.

I have been cooking in the pan for over 2 weeks now and it has been far superior to the other so-called non-stick pans in the house. I grabbed a dollar store stainless steel spatula to hold me over until I can find or make something better. Typical usage doesn't seem to do any damage to the surface. It has collected some carbonaceous bits and further blackened the surface. I have minimal experience with cast iron, and stumbled upon the links above via searches when I had decided I need to abandon the other pans a few weeks back. I will try to remember to give updates on how this pan goes, as well as the 3 pan set I got the other day.

Another small note is about how I have heard that flaxseed oil won't work on steel/stainless steel. I had an old steel oven pan that I probably should have thrown away a while ago and I decided to give it the treatment along with my 12" pan. I sanded it a bit and did half as many coats of oil and it no longer rusts and has similar non-stick properties to the cast iron pan. Things will barely stick and I can easily remove things from the surface with a spatula or cloth.

I'm going to get more sandpaper soon so I can clean up the other cast iron pans I picked up and hopefully I can replicate the results I have had so far.

I have an AUS-ION pan.

I had a tough time seasoning it initially. It’s possible that I didn’t clean it enough out of the box prior to the seasoning process.

What worked in the end was organic canola. One thin layer at a time, I’d turn the heat off once the oil had finished smoking.

I chose canola over some of the other oils in the household because it has a higher polyunsaturated content. Just an unconfirmed hunch.

I think many different things work to make a nice surface on cast iron and carbon steel. I've got two India carbon steel woks (kadhai) and I simply season them by making a batch of popcorn with vegetable oil. Works great! And then if a housemate leaves the curry leftovers in it overnight, well, damn, but I just clean it and make another batch of popcorn and it's fine again!