Making cast iron pans. 19th-century artwork showing workers in China producing cast iron cooking pans. Cast iron is a form of iron that has been prepared by casting in a mould, as opposed to later, more advanced methods of producing iron. Cast iron was used in ancient China for weapons, and farming and cooking implements. This is the stage where the casting moulds for the iron cooking pans are filled with molten iron and then cooled with water. This artwork is an opaque watercolour. It dates from circa 1820.