The Event:
From the 1850s onwards, Teesside was becoming a major centre for iron and steel production. Production technology was constantly evolving and in 1879 a new process was implemented that had a major impact – The Gilchrist Thomas Process.
The Gilchrist Thomas Process was not invented in Teesside – it was first tested at Blaenavon ironworks in Wales with the help of the manager of that ironworks, Edward Martin, who promised to assist that the inventor Sidney Thomas Gilchrist with taking out a patent.
However, it was not until 1879 when Gilchrist Thomas made the acquaintance of Edward Windsor Richards, the manager of Bolckow Vaughan & Co.’s works, that the process was put to industrial use, the success of the invention was assured, and domestic and foreign patents were taken out.
The Bessemer process – named after its inventor, the Englishman Henry Bessemer, who took out a patent on the process in 1856 – was the first inexpensive industrial process for the mass production of steel from molten pig iron before the development of the open-hearth furnace.
The key principle of the Bessemer process was removal of impurities from the iron by oxidation with air being blown through the molten iron. The oxidation also raises the temperature of the iron mass and keeps it molten.
Before the Bessemer process, Western Europe and the United States relied on the puddling process to reduce the carbon content of white cast iron (refined pig iron), converting it to wrought iron. It was possible to make low-quality puddled steel, but the process was difficult to control and quality varied. High-quality steel was made by the reverse process of adding carbon to carbon-free wrought iron, usually imported from Sweden.
However, there was a problem with the Bessemer Process: the presence of phosphorous impurities could result in low grade steel.
Thomas Gilchrist Thomas, a Londoner but the son of a Welshman, determined to solve the problem.
Whilsy working as a police court clerk, he found time to study chemistry, and attended lectures at the Birkbeck Institute. By the end of 1875 was convinced that he had discovered a method and was able to test his ideas thanks to support from his cousin, Percy Gilchrist, who was chemist at the Blaenavon ironworks.
Sidney Gilchrist Thomas’s invention consisted of using dolomite or sometimes limestone linings for the Bessemer converter rather than clay, and it became known as the ‘basic’ Bessemer rather than the ‘acid’ Bessemer process.
As well as removing the problem of phosphorous impurities, the process had another advantage: the processes formed more slag in the converter, and this could be recovered and used very profitably as a phosphate fertilizer.
The Significance:
The Bessemer process revolutionized steel manufacture by decreasing its cost, from £40 per long ton to £6–7 per long ton, along with greatly increasing the scale and speed of production of this vital raw material. Before it was introduced, steel was far too expensive to make bridges or the framework for buildings and thus wrought iron had been used throughout the Industrial Revolution. After the introduction of the Bessemer process, steel and wrought iron became similarly priced, and some users, primarily railroads, turned to steel. However quality problems meant that uses were still limited – particularly for structural projects. The Gilchrist Thomas Process helped remove some of those issues and helped Teesside become the steel production capital of the world.
The Gilchrist-Thomas Process continued to be used in Continental Europe, where iron ores were of high phosphorus content, as the open-hearth process was not able to remove all phosphorus.
Technology, however, does not stand still.
By 1895 the Bessemer process was being replaced by a new process: the open hearth method. And by the mid-twentieth century most manufacturers had adopted a process called basic oxygen steelmaking.
One of the major causes of the decline of the giant ironmaking company Bolckow Vaughan, the company that had first applied the Gilchrist Thomas Process, was its failure to upgrade its technology.
Suggested Places to Visit:
The Dorman Museum, Middlesbrough