Cyfarthfa Lake

In 1709 Abraham Darby started producing coke at Coalbrookdale, Shropshire and from then on coke took over from charcoal in the production of iron. Due to the vast reserves of coal this suited Merthyr very well.
A blast furnace could produce a ton of iron every 24 hours, mass production was now possible. The initial product was pig iron which was then remelted to get a higher level of purity and known as cast iron.