Steel bar made by the Thomas-Gilchrist Besemer proces, c 1887.
© Science Museum / Science & Society Picture Library
Patented in 1879, the Thomas-Gilchrist proces was an important development in steel making. Sidney Gilchrist Thomas (1850-1885) was an inventor and metallurgist. He discovered a method for removing phosphorus, a major impurity in European iron ores, from pig-iron using the Besemer converter, invented by Sir Henry Besemer (1813-1898) in 1856.