Cast iron is used for cookware because: it has excellent heat retention properties; it can be produced and formed with a relatively low level of technology; and it's cheap and lasts a lifetime. Seasoning is used to protect bare cast iron from rust and to create a non-stick surface.
Bare cast-iron vessels have been used for cooking for hundreds of years. Cast iron cauldrons and cooking pots were treasured as kitchen items for their durability and their ability to retain heat, thus improving the quality of cooking meals. Before the introduction of the kitchen stove in the middle of the 19th century, meals were cooked in the hearth or fireplace, and cooking pots and pans were designed for use in the hearth. This meant that all cooking vessels had to be designed to be suspended on, or in, a fireplace. Cast iron pots were made with handles to allow them to be hung over a fire, or with legs so that they could stand up in the fireplace. In addition to dutch ovens, which were developed with the onset of the Industrial Revolution, a commonly used cast iron cooking pan called a spider had a handle and three legs used to stand up in the coals and ashes of the fire.
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 a "non-stick" surface, they are also a good choice for eggs, frittata, upside down cakes, cornbread, all kinds of stews and braised dishes, and browning in general.
Most bare cast iron pots and pans are cast from a single piece of metal in order to provide even distribution of heat. This quality allows most bare cast iron pans to serve as dual-purpose stovetop fryers and oven baking dishes. Many recipes call for the use of a cast iron skillet or pot, especially so that the dish can be initially seared or fried on the stovetop; the dish is then transferred into the oven, pan and all, to finish baking. Likewise, cast iron skillets can double as baking dishes. Cornbread in particular is seen as a food item that is best prepared in a cast iron skillet: the iron pan is heated beforehand in the oven, the ingredients are combined in the heated pan, and the dish is then placed directly into the oven for fast baking.
Cast iron cookware leaches small amounts of iron into the food. Anemics, and those with iron deficiencies, may benefit from this effect.
Some more info:
- Seasoning is a process by which a layer of animal fat or vegetable oil is applied and cooked onto cast iron or carbon steel cookware. The seasoning layer protects the cookware from rusting, provides a non-stick surface for cooking, and prevents food from interacting with the iron of the pan. Enamel-coated cast iron pans do not need seasoning, as the enamel coating prevents rust in most instances.
- Cleaning Because ordinary cookware cleaning techniques like scouring or washing in a dishwasher can 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 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 scrub with coarse salt and a paper towel or clean rag.
- Brands 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 in China by All-Clad, as does Rachael Ray.
