Cast-iron cookware
Because other 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 chefs 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 is to scrub with coarse salt and a paper towel or clean rag.
Ironwork
Cast iron is produced in a furnace stoked with alternate layers of coking iron then poured into molds. After the iron cools off, the sand is cleaned off. The Chinese were the first to use cast iron from the 6th century AD using it as support for pagodas and other buildings.