Sciencemadness Discussion Board

Seasoning Cast iron - What happens in the process?

RogueRose - 29-1-2017 at 21:43

I've seen a number of processes that can be used to season cast iron cooking pans, skillets, and other cookware. The general process seems to be coating the cooking surface with an oil or fat and then heating to a high heat, allowing to cool, and repeating. At the end the oil/fat is removed by wiping out or rinsing in hot water and wiping out (no soap used).

What I have read about what the result of this process is supposed to produce is a polymerized surface on the cast iron from the fats. I'm not sure what that exactly does but I think it makes it a resistant, plastic like surface on the surface.

What I'd like to know is what oil or fat would be best to do this process. From soap making, I know that all the fats have different length fat chains and there is a wide range of smoke points, so I would assume that the polymerization points/temps would probably differ as well. Some fats may be better suited to this process and that is what I am trying to find out.

Also, I need to know what temps are best for doing this and if there is an upper limit to the process. It seems that a 500F oven may not be enough for some fats so I'm thinking of using a wood fire/stove for this.

Might there be an oil that gives better protection when heating to high temps for cooking?

I hope this question fits in enough with chemistry as I see it fully as how the oils react in heat. I don't need to be told the best oils/fats to use (open to suggestions though) but how to find them, what characteristics to look for, would help a lot.

Twospoons - 29-1-2017 at 23:08

The method I was shown by my nephew (a chef) involves warming the pan, putting in a little oil, then giving it a good scrub with salt (using a paper towel). I suspect there is a combination polishing effect with the salt, and bonding of a thin polymerized layer of oil. From memory, the polymerization is catalyzed by some metals (the basis of hardening in oil paints), I dare say iron is one of those catalysts, and the scrubbing with salt would probably introduce small amounts of very fine iron oxide into the oil layer.

However it works, the result is exceptionally good - almost completely non-stick!

S.C. Wack - 30-1-2017 at 14:29

Quote: Originally posted by RogueRose  
What I'd like to know is what oil or fat would be best to do this process.


Flax or hemp. A drying oil.

BromicAcid - 30-1-2017 at 14:36

Definitely a niche use of chemistry, and not something I would want to have to research from scratch. I read the following article sometime back and it provided an acceptable level of chemical reasoning:

http://sherylcanter.com/wordpress/2010/01/a-science-based-te...

RogueRose - 30-1-2017 at 18:07

Quote: Originally posted by Twospoons  
The method I was shown by my nephew (a chef) involves warming the pan, putting in a little oil, then giving it a good scrub with salt (using a paper towel). I suspect there is a combination polishing effect with the salt, and bonding of a thin polymerized layer of oil. From memory, the polymerization is catalyzed by some metals (the basis of hardening in oil paints), I dare say iron is one of those catalysts, and the scrubbing with salt would probably introduce small amounts of very fine iron oxide into the oil layer.

However it works, the result is exceptionally good - almost completely non-stick!


Was this done each time the pan was used or was this something that is done and then it is good for some time?

I know when I look at the cooking area like the splash guard around a grill at a restaurant there is this brown/orange tacky goo that is a result of the oils heating very hot and then adhearing to the metal, basically permenantly. This will happen on any cooking surface especially on deep fryers and frying skillets. This stuff comes off with a strong base and a good scrub pad, but usually not with soap (unless a metal scrub pad removes material from the pan/pot/etc).

Maybe I should have added the above in the first post, explaining what I thought what might be the polymer layer from oil. Does this make sense? Is that layer the polymer that is what people call "seasoning"?

I think the hemp oil sounds like a good idea to try as it has a high smoke point from what I remember.

Bromic: Thanks for that link. It looks like there might be some good info on there that could be helpful.

Morgan - 30-1-2017 at 18:55

This guy uses 2 low temperature seasonings and 2 high and in another video he mentions flax seed oil. And he has quite a few cast iron clips.
https://www.youtube.com/watch?v=Jre9ARTP978
https://www.youtube.com/watch?v=Os6iqDxQGAs

A very silvery cast iron pan
https://www.youtube.com/watch?v=fZmNyOCzpC8

Twospoons - 30-1-2017 at 19:44

Quote: Originally posted by RogueRose  


Was this done each time the pan was used or was this something that is done and then it is good for some time?


Provided I only use hot water to clean the pan (no soap) it seems to last reasonably well - as in half a dozen uses.
Probably a solid bake after oiling would yield a better result. I use olive oil, as thats what I use for cooking, but reading around it looks like flaxseed oil would be better. I think I might try it next time the pan gets a bit sticky.

macckone - 30-1-2017 at 22:39

Flaxseed oil is best. It polymerizes to a coating that doesn't chip or flake and is even resistant to soap. Multiple coatings over time works best.

Fulmen - 31-1-2017 at 01:40

Walnut, sunflower and safflower oils are also considered drying oils.

zed - 3-2-2017 at 17:47

Ummm. Well, the surface of the Iron itself, seems to be kinda porous. And, bound together by polymeric material the seasoning may be, but in my experience, the magic element IS an Element. Elemental Carbon.

Morgan - 3-2-2017 at 18:14

I think no matter what the pan, it's helpful not scratch the surface and to keep the surface smooth, as much as you might like to use a Brillo pad to scour a hard to clean mess.