Steel Heroes - Gilchrist Thomas

Sidney Gilchrist Thomas


  • 1850 – 1885
  • Bessemer Medal 1883
  • Gold Medal of the Society of Arts




Percy Carlyle Gilchrist

  • 1851 – 1935​
  • Vice President of the ISI
  • Fellow of the Royal Society 1891
  • Chevalier of the Legion of Honour


Sidney Gilchrist Thomas, conceived the idea of using a basic lining in a Bessemer converter to reduce Phosphorous. He experimented with a small scale converter, but could not get the right conditions at small scale.

In 1875, he contacted Mr Percy Carlyle Gilchrist (his cousin) who was a chemist at the Blaenavon Works, and in 1875 experiments proved his idea worked. In March 1878 he announced his discovery at an ISI meeting, and took out a patent in May 1878.  

Mr E Windsor Richards (President of the CIE in 1880) of Bolckow & Vaughan in Middlesbrough saw the process at Blaenavon, and erected two 30 cwt converters to refine the process. The cousins presented a joint paper to the ISI in May 1879, and what became known as the Thomas-Gilchrist Process was used widely and increased steel production. 

In 1881 the Dephosphorizing and Basic Patents Co. Ltd was formed with Gilchrist, Thomas and others. On Thomas’s death in 1885, Gilchrist became managing director and continued working to develop the process, also acting as a consulting metallurgical engineer. 

Gilchrist was elected Fellow of the Royal Society in 1891 and made a Chevalier of the Legion of Honour in France.  In 1916, Gilchrist was made an honorary vice president of the ISI.


Abstract for grant of patent in 1880

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