Clippings by torontoontario

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RE: cooking with cast iron (Follow-Up #2)

posted by: danab_z9_la on 03.07.2007 at 05:17 pm in Cookware Forum


I really enjoyed reading your article on the care and use of cast iron cookware. You have collected and shared some really good information. However, I'd like to point out that the claim to "never use soap" to clean cast iron is based on old folklore and has no scientific basis that I am aware of.

In the "old days" it was very common for folk to make their own soap. Soap simply is the potassium or sodium salt of a fatty is the end product of a reaction between Potassium or Sodium hydroxide with an animal or plant fat. Lard and Olive oil were used quite extensively for soap making.

Early folk boiled wood ash extract to get Potassium Hydroxide for making a soft soap. By the early 1900's lye (or Sodium Hydroxide) became readily available in cans and was the raw material of choice for making soap. One of the advantages folk realized in using lye was it produced a hard soap and they didn't have to boil all of that wood ash extract.

Folk used cast iron vessels in which to boil the wood ashes or lye, with animal fat to produce soap. One of the observations they made in the soap making process was that it removed the seasoning of the cast iron kettle. This is where the folklore to "NEVER USE SOAP" began. The error here is that it is not the soap that removes the patina or seasoning on the kettle; rather, in reality it is the Potassium or Sodium hydroxide alkalie that removes the pot seasoning.

Patina development on cast iron is a two part process. The first part involves developing a thin layer of polymerized oil on the cast iron. This is accomplished by applying a thin coat of oil to the cast iron surface and heating it in an oven until it dries to the surface. When done properly this layer of polymerized oil CANNOT be removed by either soap or dishwashing liquid. The only way to removed this layer is by vigourous mechanical scrubbing (i.e. brillo pad), by caustics (lye, draino, or oven cleaner), or by burning it off at temperatures greater than 500 deg F (on BBQ pit or in Self Cleaning oven).

The second part to true Patina development on cast iron involves the actual lay down of carbon on the cast iron surface. This happens at temperatures slightly above the smoke point of the seasoning oil. You MUST heat cast iron above the smoke point to get actual carbon black into the patina matrix. If you do not heat to the smoke point you will only have polymerized oil in the coating........this is a protective coating but it is not as slick a surface as a mixture of both carbon and poly molecules.

Keep in mind that grease splatter inside of an oven undergoes the same chemical reactions as what goes on in the cast iron seasoning process. If soaps or detergents really were able to remove seasoning from a pot, then cooks could actually clean the inside their ovens with Ivory soap or Dawn liquid soap/detergent. We all know that doesn't work and is why oven cleaner and self cleaning oven cycles were invented!

I'll comment on the following in the near future:

1) Oils used for seasoning.
2) Old cast iron is superior to today's stuff.
3) Proper cleaning procedures

Thanks for making your article available for comment.



clipped on: 04.04.2007 at 11:38 pm    last updated on: 04.04.2007 at 11:38 pm

RE: cooking with cast iron (Follow-Up #21)

posted by: torontoontario on 04.04.2007 at 08:51 pm in Cookware Forum


Thanks for your responses.

I'm wondering that if the heat of the BBQ is a good thing, would the extremely high heat of the self clean oven be a better thing?


clipped on: 04.04.2007 at 11:36 pm    last updated on: 04.04.2007 at 11:37 pm