Ancient Chinese cast iron implement moulds, c 300 BC.
© Science Museum / Science & Society Picture Library
Plaster copies. Cast iron is made by pouring the molten metal into moulds shaped according to the object to be produced. It is very strong, but somewhat brittle. Cast iron was first produced in China in the 4th century BC, and was used to produce weapons, agricultural tools and pots and pans for cooking. The availability of high quality clay was crucial as it enabled effective blast furnaces to be constructed. In addition, the Chinese discovered that using 'black earth', which contains phosphorus, in the furnaces lowered the temperature at which iron melts. The first blast furnaces in Europe did not appear until the 8th century AD, and cast iron did not become readily available in the west before 1380.