Abraham Darby used Coke instead of coal to fire blast furnaces, making the production of iron from pig iron (a weak iron), much more economical. Coke burns significantly hotter than coal which, combined with his new design to concentrate the heat, his factory was significantly more efficient than prior methods. He created the Bristol Brass Company to commercialize his method.
Interestingly, Darby initially struggled due to a relatively low demand for iron. However, Thomas Newcomen’s invention of the Newcomen steam engine vastly increased the demand for iron. Along with Newcomen then Watt’s steam engines later, Darby’s furnace is a significant contributor to the first Industrial Revolution.
Working at his plants was terrible. Child labor was common. Workers were often injured or died from burns. Carbon monoxide poisoning was also a common cause of death. It was filthy, hot, dangerous work; few workers lived to 40.
Darby himself died at 38 with his affairs a mess. Creditors took the business. However, his brother eventually regained control and his sons would go on to take over the business.
Over time, Henry Cort improved the efficiency of Darby’s process, using rolling and puddling to more efficiently purify the iron. Before Cort, workers would have to hammer the hot metal with a hammer which was both inefficient, dangerous, and hot work. Cort’s method involved rolling the molten metals which was also dangerous but about 15 times faster. Since less time was required, costs were lower and fewer workers were injured.
Finally, in 1828, James Neilson modified the Darby furnace recycling exhaust heat to preheat incoming air. This required substantially less coke, lowering costs.
The lower-cost iron opened creative uses for the metals. Early uses included tableware. Eventually, iron became vital for steam engines. Finally, the iron was being used to construct bridges. Of course, iron remained useful for making weapons just as it had since ancient times.