You can’t wash cast iron cookware with soap
March 30, 2011
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This myth seems to make sense—after all, you use fat to season cast iron and soap removes fat, case closed, right? It’s not that simple.
The seasoning layer on the surface of the pan is formed when the pan is heated while in contact with some fat or oil. This may happen during normal cooking or during a special seasoning process that many people use with a new pan. The result is a chemical reaction in which that fat polymerizes, meaning that multiple individual fat molecules join together to form larger molecules. It is these larger polymer molecules that bind to the metal of the pan and form the seasoning. And, guess what, the polymer is not dissolved by soap. So, it’s perfectly OK to use a mild soap on your cast iron if you are so inclined. Never use harsh detergent, put the pan in the dishwasher, or scrub with an abrasive, however, as these will take off the coating. You also should not cook acidic foods, such as tomato sauce, in a cast iron pan.
Of course, many people get their cast iron perfectly clean without soap, so there’s no reason to use it. The idea that soap will ruin the pan is, however, a myth.
Much new cast iron comes already seasoned. If not, it is likely coated with wax or shellac to prevent rusting, and you must remove this coating before seasoning. A good scouring with detergent will do the trick. Dry thoroughly, coat the entire surface, inside and out, with oil, and put in a 325 degree oven for about an hour. Let cool and wipe off excess oil and you are ready to cook. The best oil to use for seasoning is flaxseed oil. Lacking that, use lard or hard vegetable shortening like Crisco. Regular vegetable oils such as corn and peanut will work but are not as effective.