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Cast iron cookware is slow to heat, but once at temperature provides even heating. Cast iron can also withstand very high temperatures, making cast iron pans ideal for searing. Being a reactive material, cast iron can have chemical reactions with high acid foods such as wine or tomatoes. In addition, some foods (such as spinach) cooked on bare cast iron will turn black.
Cast iron is a porous material that rusts easily. As a result, it typically requires seasoning before use. Seasoning creates a thin layer of fat and carbon over the iron that coats and protects the surface, and prevents sticking.
Bare cast-iron vessels have been used for cooking for hundreds of years. Cast iron's ability to withstand and maintain very high cooking temperatures makes it a common choice for searing or frying, and its excellent heat diffusion and retention makes it a good option for long-cooking stews or braised dishes.
Because cast iron skillets can develop an extremely "non-stick" surface, they are also a good choice for egg dishes, particularly scrambled eggs. Other uses of cast iron pans include making cornbread and pineapple upside-down cake.
Types of bare cast iron cookware include dutch ovens, frying pans, deep fryers, tetsubin, woks, potjies, flattop grills and griddles.
Cast iron cookware leaches small amounts of iron into the food. Anemics, and those with iron deficiencies, may benefit from this effect, though those with excess iron issues (for example, people with hemochromatosis) may suffer negative effects.
Seasoning is a process used to protect bare cast iron and carbon steel cookware from rusting, provide a non-stick surface for cooking, and prevent food from interacting with the iron of the pan. This is a process similar to bluing (steel), forming an oxidizing chemical reaction with iron on the surface selectively forming magnetite (Fe3O4), the black oxide of iron (as opposed to rust, the red oxide of iron (Fe2O3)). Black oxide provides minimal protection against corrosion, however, unless also treated with a water-displacing oil to reduce wetting and galvanic action.
Seasoning is a three-step process, involving cleaning the cookware to expose the bare metal, applying a layer of animal fat or vegetable oil, and heating the cookware to bond the fat to the metal.Seasoning also occurs as a natural by-product of using the cookware to cook foods that deposit oils or fats on the pan.
New cast iron that is not pre-seasoned is often sold with a protective coating (wax or shellac). This coating must be removed (typically by scouring) to expose the bare cast iron surface before the pan is seasoned. For already-used pans that are to be re-seasoned, the cleaning process can be more complex, involving rust removal and deep cleaning (with strong soap or lye, or by burning in a campfire or self-cleaning oven)to remove existing seasoning and build-up.
Fats and oils typically used for seasoning include lard, hydrogenated cooking oils such as Crisco, and palm or coconut oil (in general, oils that are high in saturated fats, and therefore less likely to become rancid).
Heating the cookware (such as in a hot oven or on a stovetop) facilitates the oxidation of the iron; the fats and/or oils protect the metal from contact with the air during the reaction, which would cause rust to form. Some cast iron users advocate heating the pan slightly before applying the fat or oil to ensure that the pan is completely dry and to open "the pores" of the pan.
Newly seasoned cast iron will have a dark brown coating. If the seasoning process is repeated, or after prolonged use, this coating will turn glossy and black, and the non-stick properties of the pan will further improve.
Because ordinary cookware cleaning techniques like scouring or washing in a dishwasher will remove or damage the seasoning on a bare cast iron pan, these pans should not be cleaned like most other cookware. Some cast iron aficionados advocate never cleaning cast iron pans at all, simply wiping them out after use, or washing them with hot water and a stiff brush. Others note that grease left on a pan will eventually become rancid, and advocate washing with mild soap and water, and then re-applying a thin layer of fat or oil. A third approach, advocated by television chef Alton Brown, is to gently clean with coarse salt and a paper towel.
Well-established brands of bare cast iron cookware in the United States include Griswold and Wagner (now both owned and manufactured by the American Culinary Corporation, in the USA), Lodge (made in USA, though their enamel-coated line is made in China), and John Wright (some items made in China). Emeril Lagasse also has a line of pre-seasoned cast iron made by All-Clad, as does Rachael Ray.
There are many other producers of traditional cast iron in France, Italy, Denmark, Sweden and the UK, manufacturing enameled and unenameled cookware. In Asia, particularly India, Korea, Japan, and China, there is a long history of cooking with cast iron.
