We find the term ‘wrought iron’ used throughout the media and by the public to describe any decorative metalwork such as gates, balustrades, garden furniture that has, or appears to have, ornate scrollwork and hand forged elements.
In fact, wrought iron is the name given to a material that was commonly used by blacksmiths until improved production methods of mild steel (The Bessemer Process of 1856) and lower prices in the 1850’s meant that it was less commonly used. The term ‘wrought’ means ‘worked by hand’ so can be applied to the more commonly used material mild steel, as in ‘wrought steel’. Wrought iron is now only recycled (rather than commercially manufactured) on a small scale and recommended for use when specified in heritage metalwork conservation projects or for high end projects where the look of wrought iron is preferred and there is a requirement for ‘like-for-like’ materials to be used. Due to the lengthy manufacturing process wrought iron is also considerably more expensive than mild steel or pure iron.
Wrought iron is a mixture of pure iron and iron silicate that contains 0.02% to 0.08% carbon. The process for producing wrought iron involved heating pig iron (an iron with a very high carbon content – around 4% to 5%) until all of the carbon and impurities were burnt off. The remaining mass was hammered, milled, reheated and silicon slag added. Wrought iron, cast iron and mild steel are all made from pig iron.
Wrought iron has fibrous characteristics similar to wood – it will split and crack along its grain lines. The beauty of wrought iron, and the main reason it was such a popular material for external metalwork, is that it is rust and corrosion resistant. Wrought ironwork will rust down to the iron silicate and then stop.