Looking for a polymer food chemist -- technicals of cast iron seasoning.

Seasoning a cast iron skillet creates a polymer coating by heating various oils past their smoke point.

I've found that Lit is the most diverse community around, full of people who know lots of good things outside the bedroom! So, hoping an expert chemist will notice my plea...

(The internet abounds with recipes. What I can't find is information about what's happening on the molecular level. So please, don't tell me you favorite method unless you have lab data to go with it.)

It seems the best oil to use is flaxseed (food grade linseed oil) allegedly because all the omegas aid the cross-linking that builds the polymer.

My specific questions are, from a chemical engineering process view:

1. how hot does the oil coating need to get?
2. How long does it need to stay hot?
3. How fast can it be cooled?

Thank you community!

Wanting information is one thing...but how many chemists do you think hang out here?

Then again, wanting someone to do your homework...

There are a few of us

And some of us are cast iron aficionados as well

I'm a fan of peanut oil

Here's a source I trust: https://www.youtube.com/watch?v=RkfLwe8Jl4Q

Zeb_Carter said:

Wanting information is one thing...but how many chemists do you think hang out here?

Then again, wanting someone to do your homework...

Click to expand...

Zeb, my boy, I'm long, long out of school and the "home work" I do is either house-husband or DIY maintenance...

The problem is that all the info on the internet is hear-say, old wives tales, and rules of thumb. Being an engineer, I look for data and hard facts.

After posting this, several references came my way giving me strings to pull on. Lit people span the spectrum!

I can now tell you, citing academic papers, how flax seed oil behaves as temperature increases, with or without oxygen, and with or without metallic catalysts.

And it (unfiltered, unpreserved, 100% pure) is indeed much better than other common vegetable oils.

Most interesting, the easiest way to season a skillet is using ultraviolet light (295nm). If you have a bright enough light (unfiltered Xenon flash), it only takes a long minute and requires no heat.

ReadyOne said:

Seasoning a cast iron skillet creates a polymer coating by heating various oils past their smoke point.

I've found that Lit is the most diverse community around, full of people who know lots of good things outside the bedroom! So, hoping an expert chemist will notice my plea...

(The internet abounds with recipes. What I can't find is information about what's happening on the molecular level. So please, don't tell me you favorite method unless you have lab data to go with it.)

It seems the best oil to use is flaxseed (food grade linseed oil) allegedly because all the omegas aid the cross-linking that builds the polymer.

My specific questions are, from a chemical engineering process view:

Click to expand...

1. How hot does the oil coating need to get?
   Between 275 C and 325 C. 600 F is a great target.
   
   
2. How long does it need to stay hot?
   Well under 30 minutes. Probably just a couple of minutes at the target temperature, given the time to heat up.
   
   
3. How fast can it be cooled?
   Slow air cooling works (e.g. open oven door). Forced air (breezy fan) is too fast.

BTW, there are ways to reduce the temperature needed, but they aren't kitchen (or outdoor gas cooker/grill) friendly.

ReadyOne said:

Zeb, my boy, I'm long, long out of school and the "home work" I do is either house-husband or DIY maintenance...

The problem is that all the info on the internet is hear-say, old wives tales, and rules of thumb. Being an engineer, I look for data and hard facts.

After posting this, several references came my way giving me strings to pull on. Lit people span the spectrum!

I can now tell you, citing academic papers, how flax seed oil behaves as temperature increases, with or without oxygen, and with or without metallic catalysts.

And it (unfiltered, unpreserved, 100% pure) is indeed much better than other common vegetable oils.

Most interesting, the easiest way to season a skillet is using ultraviolet light (295nm). If you have a bright enough light (unfiltered Xenon flash), it only takes a long minute and requires no heat.

Click to expand...

Personally...I don't care. I married a southern girl, she knew how to season a cast iron skillet when she was five. All that other bullshit...doesn't matter.

Now if you want to talk bullet ballistics at distances greater then 1 mile, at altitudes greater than 9,000 feet...

Zeb_Carter said:

Wanting information is one thing...but how many chemists do you think hang out here?

Then again, wanting someone to do your homework...

Click to expand...

Probably more than you think.

It is about heat, time and oxygen.

Many organic oils can polymerize, the very same effect used in linseed-oil based paint.
In painting you call it "drying", and it's extremely slow in the raw oil. If the oil is boiled before use and catalysts are added, it is a lot faster. The catalysts are typically heavy metal compounds of lead, cobalt and manganese, not exactly what you want to put on your cookware.

On cookware you use time and heat instead of catalysts.
Heat it, give it a thin layer of oil, wipe it, another layer and so on has been my method.

Here is one using an oven:
http://sherylcanter.com/wordpress/2010/01/a-science-based-technique-for-seasoning-cast-iron/
It makes sense, but I have not tried it.


Because it is polymerized vegetable oil, the old layer can be removed quite easily with lye (be really careful, gloves and goggles must be worn) or oven cleaner (which is basically an expensive way to buy a mix of lye and soap).

ReadyOne said:

Seasoning a cast iron skillet creates a polymer coating by heating various oils past their smoke point.

I've found that Lit is the most diverse community around, full of people who know lots of good things outside the bedroom! So, hoping an expert chemist will notice my plea...

(The internet abounds with recipes. What I can't find is information about what's happening on the molecular level. So please, don't tell me you favorite method unless you have lab data to go with it.)

It seems the best oil to use is flaxseed (food grade linseed oil) allegedly because all the omegas aid the cross-linking that builds the polymer.

My specific questions are, from a chemical engineering process view:

1. how hot does the oil coating need to get?
2. How long does it need to stay hot?
3. How fast can it be cooled?

Thank you community!

Click to expand...

You are way overthinking this. The process can't possibly be that temperature specific it also can't possibly matter exactly which oil you use if you're going to use the cookware is going to be exposed all sorts of fats and oils that you cook with in the future which are going to be combined with what was done in the seasoning process.

ReadyOne said:

1. How hot does the oil coating need to get?
   Between 275 C and 325 C. 600 F is a great target.
   
   
2. How long does it need to stay hot?
   Well under 30 minutes. Probably just a couple of minutes at the target temperature, given the time to heat up.
   
   
3. How fast can it be cooled?
   Anything short of quenching. Forced air (breezy fan) should be fine.

BTW, there are ways to reduce the temperature needed, but they aren't kitchen (or outdoor gas cooker/grill) friendly.

Click to expand...

That's a nice oven if you can achieve 600 degrees. Throw in some pizza stones while your seasoning the cast iron and bake a pizza.

Is dinner ready yet?

I'm no chemist but Ms. Neb and I are pretty good cooks. (She's a lot better than me.) We do a LOT of it in cast iron skillets. As a matter of fact, it is my go to frying pan.

There are a lot of myths about seasoning but it is much easier than you think. It really isn't something you have to do right away. Just start cooking. It will season on its own. It just won't be as non-stick until it is seasoned. (Most new skillets come seasoned these days.)

But if you just want to season it, just about anything will any oil will season your skillet. It is the carbon you are after. Oils have different smoke and flame points so there is no one temperature. Bring any oil (vegetable, olive, peanut, corn, etc.) right to the smoke point. (Watch it. You do not want it to flash.) Just heat it as you would cook and it will be fine. That breaks down the oil and it combines with the skillet. Let it cool down before cleaning.

Don't worry if your skillet doesn't get all one color of black, especially at first. It will over time. The bottom line, just keep using it and it will get better and better.

A few other things....

Go ahead and clean it with dish soap. Some people confuse seasoning with a greasy surface. Not at all.

After cleaning, just wipe it down with a towel. You don't have to get every drop. Any remaining wetness will evaporate before any rust forms but don't just air dry it.

Some people like to heat it back up on the range to dry it. You can but just for a minute. If you let the skillet dry out completely and over heat, it will break down the surface and you'll be back at square one again. (I never heat dry the skillet.)

Don't worry about utensils. Scrape away with your metal spatula. It won't hurt it.

A good skillet is a sight to behold. I cook over easy eggs on them and they never stick! Skillets last forever. I think we have a couple that are at least 30 years old.

Good luck.

And also ... why wouldn't chemists hang out here. We all have real lives outside of our computers. It would actually be kinda interesting to know what Lit people do with the rest of their lives. (LOL - even as typing that, I realise it says way more about what I do with MY life than I really meant.)

From a chemistry point of view, the seasoning is not as much of a polymer as it is film of amorphous carbon. As the oil begins to thermally decompose, some of it will polymerize and some will form ringed compounds, but this is useless trivia as a practical matter. Regardless of the type of oil, it will start out as mostly medium length chains of carbon with hydrogen attached. Regardless of any partial polymerization that may initially occur, the hydrogen and some of the carbon oxidizes, leaving amorphous carbon. Any oil or fat will do this. Getting a good season (in a single process) that coats and sticks to the surface is more of a art. As a previous poster mention, it will eventually season itself with regular use.

ReadyOne said:

Seasoning a cast iron skillet creates a polymer coating by heating various oils past their smoke point.

I've found that Lit is the most diverse community around, full of people who know lots of good things outside the bedroom! So, hoping an expert chemist will notice my plea...

(The internet abounds with recipes. What I can't find is information about what's happening on the molecular level. So please, don't tell me you favorite method unless you have lab data to go with it.)

It seems the best oil to use is flaxseed (food grade linseed oil) allegedly because all the omegas aid the cross-linking that builds the polymer.

My specific questions are, from a chemical engineering process view:

1. how hot does the oil coating need to get?
2. How long does it need to stay hot?
3. How fast can it be cooled?
   

Thank you community!

Click to expand...

Well, my cast iron pans live in the oven and I use them often. Lodge has a website that will tell you how to season a new pan, but I believe that most of them nowadays are already seasoned.
If I have to reseason mine, I put a light coat of oil all over it, put it in the oven, put a sheet pan under it (one larger than the skillet) put the oven on 350° and leave it in there for at least 45 minutes. Then I turn off the oven & let it cool down for at least an hour. Take the pans out, wipe the cast iron down good & put it back in the stove. Now, I've got one that's huge, like 14" and if that one has to be done, I put it in the fire when I'm burning limbs & stuff. Some folks will say "oh, never put your cast iron in fire or hot coals...it will ruin it". That's just plain dumb to me. How is it going to ruin it? Fire is how they make it in the first place. I'm not gonna put it in 5000° heat and melt it down...and I'm not gonna leave it in there for more than about 15 or 20 minutes anyway. Sorry for rambling!!!

When it comes to the kitchen, I will take grandma's word over a scientist 9 days a week. The only thing she would use is lard. I think bacon grease would work as well, because it is basically seasoned lard. Why animal fat over vegetable oil? It tends to hold up better under the high heat that you use to season and use cast iron.

I would use the grill instead of the oven because the process stinks. Coat the pan well, including the outside, handle, pretty much the whole thing. Use your hands instead of a brush. Don't be afraid to get them messy. Do the process twice.

Here's my empirical results

After my literature search, I though I could easily develop a recipe that worked fastest at lowest heat. The literature omits a few important details, possibly because it was more focused on the resultant coating than its production.

The following observations/conclusions are my own, purely empirical, and with no controls and little data collection.

1. There are two different polymers, a low temperature one that reminded me somewhat of rubber cement, and a second one produced at high temperature.

2. The high temperature one (650+ F, 345 C) is the desirable one, and the pan can not be force cooled or it will flake. Cracking open the oven door is OK, but removing the pan to rack cool in still air risks flaking.

3. The high temp polymer is actually glue for a carbon coating. You need the heat first to make the polymer, then to create the carbon coating the polymer will bond to the iron.

4. I could not get a good finish using a thick oil coating as part of the coating would stick in the low temp rubber stage. A very long bake period might have forced it to the next stage, but I didn't try.

5. 20 minutes at >650F (345C) seems sufficient. I pushed a couple of tries past 800 F (425 C). The coating formed quicker. In my totally subjective opinion, it was perhaps better than the 650 F coating.

6. Temperatures under 600 F are not great, or need a very long time (hour?) to bake (and none of my bakes went over 40 minutes).

For those who care, it seems you need enough heat to get the peroxide radicals involved in the polymerization. The lower temperatures just get the hydroxyls involved. But low temperature oxidation of Flax/Linseed gives off an awful lot of energy, which is why rags used to apply linseed oil finishes are notorious for spontaneous combustion.

I sometimes wish I were back working at the university where I could get people with fancy equipment (how about an electron microscope?) interested. I'm very surprised this has not be the subject for a master's thesis. Or maybe it has been done, and is lost in the pre-google index age.

LOL!

I don't even know when I learned to cook eggs, over easy using bacon grease in a cast iron skillet. I thought cooking with cast iron was a basic cooking skill.

Almost drove my ex-wife crazy. I flipped the eggs over and heard a GASP behind me and a "How in Hell did you DO that without them sticking?"

She never did learn how to cook with cast iron... my WOK disappeared also!

Not that she ever tried using it...

ReadyOne said:

Seasoning a cast iron skillet creates a polymer coating by heating various oils past their smoke point.

I've found that Lit is the most diverse community around, full of people who know lots of good things outside the bedroom! So, hoping an expert chemist will notice my plea...

(The internet abounds with recipes. What I can't find is information about what's happening on the molecular level. So please, don't tell me you favorite method unless you have lab data to go with it.)

It seems the best oil to use is flaxseed (food grade linseed oil) allegedly because all the omegas aid the cross-linking that builds the polymer.

My specific questions are, from a chemical engineering process view:

1. how hot does the oil coating need to get?
2. How long does it need to stay hot?
3. How fast can it be cooled?

Thank you community!

Click to expand...

I've been told that nowadays when you buy cast iron, it's already seasoned, I don't know, but I'm from the south and although everybody has their own way of doing things...this is how I seasoned mine:

...put your oven on 350F; coat your pan inside & outside (handle too) with a light coating of vegetable oil or Crisco (that'd be shortening)
...put the pan in the oven upside down; put a sheet pan larger than your cast iron pan on the shelf under the pan (this is to catch any oil or shortening that drips off)
...leave it in the oven about 30 to 45 minutes (it's gonna smoke & stink, but that's ok as long as the oven ain't on fire)
...turn the oven off and let the pan cool off with the oven, usually about an hour
...once you take the cast iron out of the oven (and the sheet pan, gotta wash that), use a paper towel and wipe it down. If you find sticky or tacky spots, you used too much oil, but it don't matter.
...put the cast iron back in the oven & when you get ready to use it, it'll be ready.

I've used cast iron all my life and I've hardly EVER had any problems with it. Some folks will say "don't put it in the dishwater, you'll ruin it!" or "don't put it in a fire to 'burn it off', you'll ruin it!" Listen...first of all, putting it in the dishwater ain't gonna ruin it. The only time that's gonna happen is if you don't dry it good and it may start to rust. Putting it in the fire will NOT ruin it! My Daddy used to do that with Mama's pans (which I have two) and it never ruined it. How the hell do you think they make cast iron???? Yes, you can put it in a fire (like when you're outside burning old dead tree limbs & it's hot). Just don't leave it in there till it's orange, cause THAT will ruin it!! Daddy would leave them in about 20 minutes & take them out by the handle with a pitchfork. He'd rinse it off with the hose, Mama would put Crisco on it & put it in the oven.

Sorry for rambling!!