What is the difference between wrought iron and cast iron?
Wrought iron is traditionally smelted at a relatively low temperature in the solid state to produce a spongy mass of metal called a bloom from which the impurities were driven off as liquid slag by hammering, hence the term “wrought” ie “worked” iron. Wrought iron is very pure, with a carbon content of less than 1%, which makes it resistant to corrosion, strong in tension and malleable. By comparison, cast iron, is smelted at much higher temperatures in the liquid state, and so becomes saturated with carbon from the furnace fuel, up to about 5%. It is then poured out (ie cast) into a mould to produce blocks traditionally known as pigs hence the name “pig iron”. The high carbon content makes cast iron very rigid in compression, but weak and brittle in tension, even when red hot, so it cannot be forged or rolled. Wrought iron is a much safer material for holding the weight of a countertop than is cast iron.
