Cast iron
Cast iron is made from pig iron, which is the product of smelting iron ore in a blast furnace. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are then added to the melt before the final form is produced by casting.
Cast-iron cookware
A proper cast iron seasoning protects the cookware from rusting, provides a non-stick surface for cooking, and reduces food interaction with the iron of the pan. However, exposure to acidic foods such as tomatoes removes the seasoning, and the cookware must be re-seasoned again. Enamel-coated cast-iron pans do not need seasoning, as the enamel coating prevents rust in most instances. It is recommended to maintain the seasoning frequently to keep the food from sticking to the iron.