Science of Seasoning Cast Iron Cookware

[smuscarella]

Introduction:

Hello Everyone. I'm working to develop an airtight, scientific explanation of what happens during the seasoning process of cast iron cookware and I'm still missing a few key details.

 

Overview:

Seasoning = applying thin layers of fat to cookware and then heating (usually in the oven). The objective, over the course of multiple rounds, is to bake on layers that blacken the pan, protect the iron from rust, and provide a non-stick cooking surface.

 

The lore surrounding seasoning is both extraordinary in volume and diverse in opinion. Everyone and their grandmother (literally) has an opinion of how it should be done. And they all provide their anecdotal evidence --"it works for me!" But "works" is a subjective word and it seems there are techniques that are far better than others.

 

Objective:

To provide a comprehensive set of science-backed theories that act as solid guidelines for the individual pursuing his or her own seasoning methodologies.

 

 

Background Material:

1. There are two methods outlined that yield good results, but understanding why and how they work, is still not 100% clear, mostly because they seem to contradict each other.
2. The Sheryl Canter Method which states that flaxseed oil is THE oil to use because it's a drying oil. It has a low smoke point of 225F, but Sheryl recommends baking at 450F or higher reasoning that an oil needs to heat above its smoke point in order to release the free radicals which lead to polymerization. Sheryl also states that flaxseed oil will produce the hardest polymer. This method takes at least 6 rounds.
3. The Jeffrey Rogers Method uses Crisco vegetable shortening that has a smoke point of 440F. Jeffrey seasons at 400F for two hours. Through home experiments he found that 500F for an hour blackened the pan but did not leave it shiny. And 400F for one hour led to a gummy residue left on the pan. This method takes 2-3 rounds. Jeffrey highly discourages using flaxseed oil due to issues with flaking.
4. Additional articles that seem on target, but lacking in scientific citation: Article1 and Article2.

Research:

1. Two reactions (should) occur: polymerization and carbonization.
2. Polymerization works best (only works?) with an oil high in polyunsaturated fat.
3. Both reactions require heat.
4. More heat --> faster reaction.
5. Too little heat = gummy oil residue result
6. Too little time = gummy oil residue result
7. Most home ovens only go to 450-550F
8. In order to prevent a spotty finish, extremely thin layers of oil are needed so oil doesn't pool. (Compare first two photos with second two.)
9. A cast iron piece placed in the self-clean cycle of the oven (900F) will turn everything on its surface to ash and will leave just bare cast iron.

Questions:

1. What is actually happening when I place my oily cast iron in the oven? If it is just polymerization and carbonization, how do those things work? The oil polymerizes and then if I continue to heat it in the oven under the same heat it will begin to carbonize? Or do both things happen at the same time? How can my understanding of this process point me in the right direction for choosing an oil, oven temperature, and duration?
2. How does my choice of oil affect the seasoning process? Polyunsaturated is pretty well covered, but what about smoke point? Other factors?
3. What temperatures should I use? Does it depend on the oil? Does it depend on the smoke point? If I heat at 500F or more for too long will I just burn everything off similar to what happens in the self-cleaning cycle?
4. What is the chemical composition of seasoning? Is it the same whether I use crisco, flaxseed, canola, grapeseed, etc...?
5. How do I get the most durable seasoning?
6. Why would the flaxseed oil seasoning flake off?

 

[Becki182]

This is a really different but interesting experiment to be conducting. unfortunately, im doing animal biology so really im of no help whatsoever but thought id post encouragement for your idea!

[smuscarella]

Thanks for the support Becki!