Darby Invents Coke-Smelting

Abraham Darby developed a coal-based process for smelting iron ore. This process facilitated a major shift in the West from manufacturing predominantly with commonly available organic materials to manufacturing finished products out of mineral components that were themselves industrially produced. Had this shift in the nature of manufacturing not occurred, the Industrial Revolution would never have come about.

Summary of Event

The iron industry of the eighteenth century was based largely on methods that dated back to ancient times. Iron ore was first processed, or “smelted,” in furnaces heated with charcoal made from wood. The temperature was raised to a high enough level to melt the ore by blowing air on the fire through a bellows. The pig iron thus produced was then mostly reheated to remove any remaining chemical impurities. The resulting bar iron could be worked into useful products such as nails or horseshoes, but it took eight tons of wood to produce two tons of charcoal, which in turn could smelt one ton of pig iron. With the wood supply diminishing in eighteenth century Britain, determining how to smelt with abundant coal rather than wood was increasingly necessary. Abraham Darby discovered how to do it. [kw]Darby Invents Coke-Smelting (1709)
[kw]Smelting, Darby Invents Coke- (1709)
[kw]Coke-Smelting, Darby Invents (1709)
[kw]Invents Coke-Smelting, Darby (1709)
Coke-smelting[Coke smelting]
Iron manufacturing
[g]England;1709: Darby Invents Coke-Smelting[0250]
[c]Inventions;1709: Darby Invents Coke-Smelting[0250]
[c]Manufacturing;1709: Darby Invents Coke-Smelting[0250]
[c]Science and technology;1709: Darby Invents Coke-Smelting[0250]
Darby, Abraham
Darby II, Abraham
Smeaton, John
Darby III, Abraham
Wilkinson, John

Darby was born around 1678, near Dudley in Worcestershire, the son of John Darby and Ann Bayliss, both of them firmly committed Quakers. John Darby may have been a nail maker and locksmith, which activities (as was common in those days) he combined with farming. He apprenticed his son to a maker of malt mills, probably in Bristol.

When Abraham Darby had completed his apprenticeship, he set up in business in Bristol in 1699 as a malt-mill maker. By 1702, however, he had switched to the manufacture of brass castings, in cooperation with several friends. This business was incorporated in 1702 as the Bristol Brass Wire Company. In 1704, Darby journeyed to the Netherlands, reputed at the time to be the most advanced in the manufacture of brass items, and recruited a number of Dutch workmen to return to England with him. With their aid, he experimented with manufacturing in iron rather than brass, making cooking pots using sand molds. While cast-iron pots had been made before, the use of pure sand, without reinforcement with loam or clay, was new, and in 1707 Darby took out a patent on this process. Although it is not now known exactly how he managed to make the “bellied” iron pots for which his firm became famous, modern investigators speculate that he may have reinforced the molds with an outer rim, perhaps one made of wood.

Because pots made of iron were substantially cheaper than those made of brass, Darby rightly surmised that there would be a large market for them. To meet this demand, he needed larger production facilities, and these he found at Coalbrookdale, Coalbrookdale, England on the banks of the Severn River, Severn River, England in Shropshire. Mining was not new to Coalbrookdale, but Darby, who leased the property in 1709, had in mind a substantial expansion of the operation there. Luckily for him, Coalbrookdale combined three ingredients that made this expansion possible: readily available fuel in the form of coal, iron deposits near the surface, and a rapidly flowing stream that could supply water power.

Darby proposed to use the local coal, rather than charcoal made from wood, to smelt his iron ore; while previous efforts to do so with coal had been unsuccessful, Darby succeeded by “coking” the coal prior to using it in the smelting furnace. The resulting iron was not degraded by sulfur, as it would have been had raw coal been used, since smelting required loading the ore directly onto the fire. The innovation of converting to coal, of which substantial deposits existed in Britain, from charcoal made from trees in the rapidly disappearing forests of England set England on a new industrial path.

Darby died in 1717, before his operation had realized its full potential, but his widow and some of his Quaker associates carried on, incorporating the operation as the Coalbrookdale Company. In the period after his death, the company expanded, building a second furnace and adding several reverberatory furnaces, in which the pig iron they produced could be remelted and converted into bar iron, whose chemical properties differed from the pig iron produced directly in the smelting furnace. In this way, the company could supply not just the cooking pots that Darby had envisaged but also the specialty iron needed by the Birmingham and Sheffield manufacturers of many products made of malleable bar iron.

In 1730, Abraham Darby II, only six at the time of his father’s death, took over operation of the company. He expanded the use of coke in the smelting of iron ore, eventually producing pig iron that had many of the qualities of the bar iron that existing manufacturers of tools and small iron products required. He also expanded the operations of the company by making many of the parts needed for the manufacture of Thomas Newcomen’s steam engine, which was spreading rapidly throughout the country.

Darby’s son installed the first Newcomen steam engine at the Coalbrookdale works in 1743, using it to pump water back upstream, so the water wheel that operated the bellows could be kept in continuous operation. Increasing the capacity of the bellows allowed the smelting furnace to be operated at a higher heat, leading to a more refined iron. The bellows effect was enhanced by the father of civil engineering, John Smeaton, who devised tubes that increased the airflow. The advantages of these techniques became widely known quite quickly, and they spread rapidly throughout the industry, adding to the market for steam engines and for the cast-iron parts for them made at Coalbrookdale. The production of pig iron increased dramatically in Britain in the second half of the eighteenth century. About half of this pig iron was used for castings, the remainder being further refined into bar iron.

The operations at Coalbrookdale expanded under both Abraham Darby II (who died in 1763) and his son and successor, Abraham Darby III. By the mid-1770’s, the furnaces at Coalbrookdale and others owned by the Darbys were generating revenue of some £80,000 per year. The third Abraham Darby was best known, however, for his bridge over the Severn River, the first such bridge made of cast-iron parts and surviving into the twentieth century, though it had to be restricted to a footbridge as bridge traffic grew. It eventually became a museum.

Their Quaker affiliation led the Darbys to become enlightened industrialists, building houses for their workers and refusing to patent some of their innovations so as not to restrict their use. Despite this benevolent administration, however, Coalbrookdale lost the lead in innovation in the late eighteenth century. The casting of cylinders for steam engines was fundamentally altered by the development of reliable boring methods by Isaac Wilkinson and John Wilkinson. They manufactured tightly fitting parts for the steam engines of Matthew Boulton and James Watt, which began to displace Newcomen engines in the last decade of the eighteenth century.


The work of the Darbys set the stage for the transformation of Britain, and subsequently the rest of the “developed” world, the world that put machines to work in place of men. The production of better-quality iron started by the Darbys was absolutely essential to the coming of this Industrial Revolution; it made possible the improvements in the steam engine that enabled later models to produce far more power than the earlier ones, which had mostly been used to power pumps. It made possible as well the development of the machine tool industry, which in turn made possible the production of ever more elaborate machines to do the work that once had been done by humans, or by low-power machines activated by wind and water. Without the achievements of the Darbys, much of the rest of the Industrial Revolution would not have been possible.

Further Reading

  • Ashton, T. S. Iron and Steel in the Industrial Revolution. Manchester, England: Manchester University Press, 1924. An old but still useful account with many details about the Darby operations.
  • Cardwell, Donald. Wheels, Clocks, and Rockets: A History of Technology. New York: W. W. Norton, 2001. Although a survey, contains a short description of the Darbys’ achievements.
  • Fyrth, H. J., and Henry Collins. The Foundry Workers: A Trade Union History. Manchester, England: Amalgamated Union of Foundry Workers, 1959. Although primarily a history of the union, contains some introductory material on the Darby family.
  • Hyde, Charles K. Technological Change and the British Iron Industry. Princeton, N.J.: Princeton University Press, 1977. An absolutely essential work for an understanding of the developing iron industry. Hyde makes it clear that innovations were driven by prices.
  • MacLeod, Christine. Inventing the Industrial Revolution: The English Patent System, 1660-1800. New York: Cambridge University Press, 1988. Although the Darby family used the patent system only once, to patent its technique of casting with sand, the author has some interesting details about the application of the system to the Darby expansion.
  • Raistrick, Arthur. Quakers in Science and Industry. New York: Augustus Kelley, 1968. A reprint of an earlier work, with added information about the Darby family and the influence of their Quaker faith on their actions.
  • Schubert, H. R. “Extraction and Production of Metals.” In A History of Technology, edited by Charles Singer, E. J. Holmyard, A. R. Hall, and Trevor I. Williams. Vol. 3. Oxford, England: Oxford University Press, 1957. Describes Darby’s achievements in the context of technology through the ages.

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