Henry Bessemer (1813 – 98)

The ‘Bessemer converter’ was one of the most important technological innovations of the nineteenth century. It enabled the production of large quantities of mild steel, a material that combined the qualities of cast iron and wrought iron and was used everywhere to make the objects of the modern world – railways, ships, machines, bridges and buildings.

Although best known for his work with steel, Bessemer was a professional inventor with 129 patents across many industries. He came from a Huguenot family of printers in the south-east of England. His father, Anthony Bessemer, went to France as a young man to work for the Paris mint but returned to England during the French Revolution and began a type-foundry.

After elementary school, Bessemer educated himself in his father’s workshop, experimenting with lathes and the metal used to cast printing type. He began his career as an inventor aged 17 when his father moved his business to London. Early inventions were in electroplating, type composing, sugar refining, glass making, the manufacture of pencils, and a technique of perforating paper with needles to stamp official documents – still seen in passports. His most profitable early invention, in 1843, was to make bronze powder by machine more cheaply than the hand-made product from Germany. He bought a fine house and offices in London and created a large laboratory.

When Bessemer noticed during the Crimean War that cannon made of cast iron broke easily, he decided to investigate a better material. With little knowledge of the iron industry, he tried an original idea of blowing air through molten iron in an open crucible – his ‘converter’. It produced a violent reaction as carbon and silicon in the iron were oxidised. The result was the new material mild steel. It was ideal for many uses and cost far less to make than wrought iron. 

He published the discovery in August 1856 but he had not understood the chemistry. Other specialists perfected the process, especially Robert Mushet in England, who added ‘spiegeleisen’ to stop over-oxidation, and Göran Göransson in Sweden, who improved the air flow in the converters. In 1858, Bessemer opened his own steelworks in Sheffield. Other companies took licences and production with the process grew rapidly, especially after 1879, when Sidney Gilchrist Thomas at Blaenavon in Wales invented a lining of the converters so common phosphoric iron ores could be used.

Bessemer retired from industry in 1873 and returned to inventing, working on the grinding of lenses and a steamship that reduced seasickness. He was knighted in 1879. Several towns were named after him in America.