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 an iron-containing raw material is pounded and sieved before being placed in a mould. This artwork is an opaque watercolour. It dates from circa 1820.