Cort Improves Iron Processing

Date 1783-1784

Henry Cort developed an economical and quick method for making bar iron (wrought iron) that allowed Britain to go from being an importer to an exporter of this important material needed for industrialization and the military.

Locale Fareham, England

Key Figures

• Henry Cort (1741?-1800), English iron manufacturer
• Abraham Darby (c. 1678-1717), English iron manufacturer
• Adam Jellicoe (d. 1789), dishonest father-in-law of Cort’s partner

Summary of Event

Iron was an important industrial and strategic material in the eighteenth century for Britain. Existing technology and available resources restricted Britain to the commercial production of pig iron (cast iron) using charcoal fuel early in the century. The resulting cast iron with its high carbon content was too brittle for many uses, and the forests needed to provide the charcoal were depleting rapidly. Bar iron used to make the purer and malleable wrought iron had to be imported form Sweden and Russia. Henry Cort’s development of the “puddling” process associated with a grooved rolling mill provided a solution to these problems.

Henry Cort was born around 1741 in Lancaster, England, where his father worked in construction and as a brick maker. Cort spent ten years as a young adult working in London as a purchasing agent for the Royal Navy. In this job, Cort would have become very knowledgeable about the problems with British iron. The Royal Navy had rejected the British-produced wrought iron of the day as of too poor quality for use. Cort left this job in 1775 to take over the Fontley (Funtley) ironworks near Fareham on Portsmouth Harbour that had been inherited by his wife from her uncle, William Attwick. Samuel Jellicoe joined him as a partner.

Cort’s aim was to develop a commercial method of producing good-quality wrought iron from British pig iron and coal. Cort put a great deal of effort and money into experiments to determine the best way to achieve this goal. Cort’s efforts were the next step in a process that had been ongoing during the 1700’s. Abraham Darby of Shropshire had made the vital discovery of how to smelt iron with a coal in 1709. The process was improved over time at the Darby family ironworks at Coalbrookdale, but the next step of using coal successfully to refine pig iron to wrought iron was yet to be taken.

In 1766, Thomas and George Cranage of Coalbrookdale incorporated the use of a reverberatory (air) furnace to try to refine pig iron into wrought iron in order to prevent contaminants from the coal fuel from getting into the iron. Another important step was the invention of the steam engine first patented by James Watt in 1769. The steam engine would allow the whole process to use mechanical power. Nor was Henry Cort the only person working on the problem. A patent recorded in 1783 for Peter Onions of Merthyr Tydvil, Wales, describes a “puddling” process similar to Cort’s. There is no evidence that the two had any contact, and Onions’s work was not generally known by the iron industry.

Cort patented the grooved rolling mill process in 1783 and the “puddling” furnace in 1784. “Puddling” is the method that Cort developed to convert pig iron into wrought iron. The pig iron from a blast furnace is heated in a coal-fired reverberatory furnace. The flames and smoke of the furnace can be directed away from the iron to avoid adding more carbon to the iron. The molten iron is stirred with an iron rod to expose as much of the iron as possible to the air. The carbon is oxidized and separated from the malleable iron mass. The iron mass is then removed from the furnace and is hammered and rolled at the proper constant temperature to force out the slag (waste material) mixed within the iron and to give the iron product the desired shape and properties. Cort’s addition of a grooved rolling mill significantly reduced the need for hammering and provided a big saving in time and effort.

The resulting wrought iron from the Cort process is of good quality. The process is wasteful of iron in that as much as 20 percent of the iron can be lost, but the process is also able to produce significant amounts of wrought iron quickly. The blast furnaces of Britain were capable of producing large amounts of pig iron, and the ability to keep up was more important for the iron refiners than the concern about wasting iron.

After some initial skepticism, the Cort process was rapidly accepted by the major ironworks of Britain and became the dominant iron-refining technology in Britain. The Royal Navy soon approved its product for use. There was more debate about how much credit Cort should be given for the technology. However, prominent individuals like James Watt and Lord Sheffield (John Baker Holroyd) praised his accomplishment. The importance of Cort’s technical achievement is not really based on new discoveries. Most of the methods used in his patents were already known. The true achievement was in how the methods were improved and united into one simple, continuous process from iron ore to bar iron that could be used commercially.

Despite the importance of Cort’s technical achievements, he was not able to benefit from them financially. Cort had borrowed money from his partner’s father, Adam Jellicoe, who was the deputy paymaster of seamen’s wages. The loans were secured with Cort’s patents. When Adam Jellicoe died in 1789, it was discovered that he had embezzled public funds. Since some of the money had gone to Cort for his work, Cort was held immediately liable for the debt by the court and lost his patent rights and property in lieu of payment. Cort was financially ruined. Protests on behalf of Cort led to a small government pension in 1794. Cort died in 1800 and was buried in Hampstead, England.

Significance

Before Cort’s improvements in iron processing, Britain’s ability to produce domestic iron products was limited. The domestic ironworks had to be located in remote, forested areas to make use of the available charcoal. Iron production was limited to cast iron. The brittleness of cast iron makes it unsuitable for many important uses, and large quantities of bar iron to make wrought iron had to be imported from Sweden and Russia at high cost. Cort’s iron processing improvements allowed the economical and large-scale production of wrought iron in Britain while using domestic coal and iron resources. In 1780 before the introduction of Cort’s processing improvements, the annual production of iron in Britain was 90,000 tons. By 1820, with eighty-two hundred Cort furnaces in operation, the annual iron production was 400,000 tons.

The quick spread of Cort’s iron processing improvements was vital for Britain’s early industrial development and strategic position. The improvements freed the iron industry from its dependence for fuel on the rapidly depleting forests of Britain. Building ironworks near coal mining districts instead reduced the overall transportation costs of the industry. Britain no longer had to depend on imports of bar iron from Sweden and Russia. Trying to import bar iron during the approaching Napoleonic Wars would have represented a significant strategic liability for Britain. The availability of large amounts of affordable wrought iron was an important factor in the success of important sectors like the railroad system and the navy, as well as the British Industrial Revolution in general.

Bibliography

Deane, Phyllis. The First Industrial Revolution. London: Cambridge University Press, 1965. Examines the economic development of Britain during 1750-1850. Chapter 7 is on the iron industry and includes a discussion on the impact of Cort’s improvements.

Mantoux, Paul. The Industrial Revolution in the Eighteenth Century: An Outline of the Beginnings of the Modern Factory System in England. Chicago: University of Chicago Press, 1983. An economic history of the rise of manufacturing in England. Chapter 3 examines the coal and steel industry. Section 3 of this chapter is about Cort’s technology.

Mokyr, Joel, ed. The British Industrial Revolution: An Economic Perspective. 2d ed. Boulder, Colo.: Westview Press, 1999. A series of essays on the economic history of the British Industrial Revolution.

More, Charles. Understanding the Industrial Revolution. New York: Routledge, 2000. A good economic overview of the Industrial Revolution. Cort is discussed in Chapter 5 on inventors and entrepreneurs.

Smiles, Samuel. Industrial Biography: Iron Workers and Tool Makers. Reprint. McLean, Va.: IndyPublish .com, 2002. An electronic-book reprint of the classic 1863 work. Henry Cort and his inventions are topics of chapter 7.