Sidney Gilchrist THOMAS

Inventor and humanist

steel memory

Olivier C. A. BISANTI

  • Genuine version :
  • translation : Karen BURNS

  • first publication :
    april 04, 2001

    Amongst the technical inventions which contributed to the construction of the contemporary world, some produced changes that were so important that they constituted a demarcation line with the past, marking a border between "before" and "after".
    Such was the advent of the basic converter process. While making possible the hitherto non-exploitable ore transformation, this process changed the relative power of the nations in a world where the steel industry conditioned economic and military power. This mineral richness, suddenly became a source of power and a stake that weighed on European history between 1870 and 1980.
    Yet this invention was only the work of an amateur. His passion for metallurgy led Sidney THOMAS, obscure clerk in a London court of justice, to a decisive breakthrough in the steel industry. His premature end, his humanism and amateurism combined to make his life a singularly romantic episode in the history of industry.


    London 1850

    Sidney Gilchrist THOMAS was born on April 16th 1850 in London, capital of the British empire at the peak of its colonial power and industrial revolution. He had an elder brother; a younger brother and a sister. The whole family liked to read, and the three brothers benefited from their stays in the country to study botany and birds. The elder brother started studies in medicine. In spite of his youth, Sidney, who was a good schoolboy, was tempted by the same orientation. But his father, who would have preferred to see him orientated more towards pure sciences, disappeared brutally when he was only 17 years old.

    Portrait of Sidney THOMAS >

    The disappearance of a parent is always a tragedy and prejudicial, but this event must be taken into consideration in the context of the contemporary Victorian England of Dickens. The financial standing of the home, made up now of a woman alone with four dependent children, is immediately compromised. Sidney gives up any medical ambitions and finds an obscure job as a clerk in a court of justice in London. But he doesn't give up his interest for sciences, and is enrolled in evening courses for metallurgy.

    A metallurgical revolution

    (*) Before, steel was obtained by 'puddling', i.e. by hammering "pasty iron magnifying glasses" obtained by starting the refining with the cast iron flame in a foundry air furnace. The low temperature of 'puddling' (1300°C at the most) did not allow the reduction of the phosphoric acid by the carbon, and permitted a "natural" and completely accidental dephosphorization....

    At that time, the production of steel was mainly ensured by the Bessemer converter, which appeared in 1858, and which revolutionised the steel industry(*). Very effective on pig iron and cast iron haematites, this process alas gave only 'fragile' steels when it converted the pig iron and cast iron phosphorous issued from the majority of British ores. Bessemer easily eliminated silicon and carbon from cast iron, but the phosphorus, even oxidized by the flow of air crossing the bath, was reduced at high temperature by residual carbon, and remained in the metal.

    Bessemer converter :Filling, Blowing, Cleaning, Pouring (Positions taken by the converter during a heat >

    (*) Acids and bases were reciprocally neutralised by giving out salts and water. For phosphoric acid this was a favourable reaction. This neutralisation unfortunately destroyed the acidic silica walls, of the Bessemer converters. Silica was chosen by Bessemer because of its resistance to heat (fusion of silica: 1800°C, for a bath temperature of around 1600°C) and its simplicity of implementation (garnishings could be made with simple rammed sand).

    It would be necessary to be able to fix this phosphoric acid P2O5 on a base (*) such as lime (after thorough elimination of the carbon, i.e. at the end of the refining), but any basic substance added to the slag tackled the acidic silica garnishing of the Bessemer retort. They tried to line a retort with lime, but this coating had no bonding strength and did not hold. At this point of time Sidney THOMAS was interested in magnesia, which was also basic, which would resist the lime poured in the slag, and which could be agglomerated with tar as bricks. These bricks, once cooked, could line the retort; an additional advantage and a better heat resistant (the bath usually reached temperatures of about 1750°C).

    (*)It is only at the end of the Fifties that one realizes that because of the disappearance of carbon in the bath increases the temperature of liquidus more quickly than the ambient temperature. Part of metal is solidified. It is the energy contribution related to this change of state which allows to pass the end of decarburization and to reach the phase of dephosphorization under conditions optimal: indeed, it is led better to "low" temperature!.

    Percy GILCHRIST, a cousin of THOMAS, chemist, is interested in the project. However, lmes two young people do not have money nor of notoriety, and to find a factory to test the process is not easy. They manage to convince MARTIN, director of the steel-works of Blaenavon for an experimentation. The process functions immediately, even if one is not in a position to analyze exactly what occurs in the retort. As in Bessemer, the reaction is very fast (less than twenty minutes), dephosphorization intervenes during the three last minutes under thermal conditions particularly périlleuses(

    Steel and the ground

    (*) The method for enriching arable land with the finely crushed basic slag was developed in Germany.

    The slag lime, having collected the phosphorus, was in the slag run at the same time as the steel. Sidney THOMAS, who had still kept his concern for others, then completed his work. Phosphorus, extracted from mines and imported at great expense, was far too expensive for many small farmers, but was very much used as manure in agriculture. Sidney THOMAS proposed to provide this phosphorus by using the slags from steel-works exploiting his method (*). The patents for the basic Bessemer steel plant process were taken out in 1877; less than ten years later, in 1887, there was already 2 million tons of basic slag being consumed in agriculture.

    slag grindering at UCPMI's HAGONDANGE steelworks-Click picture to enlarge

    The sandy ground which was too acid, particularly in Germany, was amended by the basic slag, whose lime neutralized the ground acidity and whose phosphorus doped the assimilation of the carbon and nitrogen in the air and plant growth. In a letter to his cousin Percy GILCHRIST, Sidney THOMAS forecasted that the trend of the prices for ores and products would one day make slag the principal product, and steel the by-product. These days came towards the end of the Second World War.

    Sidney Thomas in the world

    In 1881, Sidney THOMAS left for the United States to negotiate his patents there. His association with Andrew CARNEGIE, the "king of American steel", got him into many conferences and presentations. He returned to England and went back and forth to the European continent and in 1882, set out again for South Africa. All these voyages tired him; he suffered particularly from seasickness during the interminable crossings. From South Africa, he passed to India, then to Australia. In all these countries, THOMAS was interested in the living conditions of the populations, and particularly those of the working men. On his return to America, he crossed from San Francisco to Pittsburgh, visiting everything that glowed. He was more and more tired. It was not only the fact of the voyages and the conferences: Sidney THOMAS was sick, as his travelling companion diagnosed, being,...a doctor.

    The last years

    THOMAS steelshop at UCPMI's HAGONDANGE steelworks-Click picture to enlarge

    On his return to London, he was submerged by the load for the administration of his patents and the technical correspondence related with their processes. Increasingly weak, he went to the English countryside, then, finally convinced of the benefits of a dry climate, left for Algeria. It took several weeks of acclimatisation to the extreme heat (he badly chose his season of arrival). In no state to return to England, he was so bored that he had his metallurgical apparatus dispatched. He employed a young Arab to do the tests which he no longer had the force to achieve himself. This young man "carried out his job with the greatest gravity".

    During the phase of acceleration of his disease, Sidney THOMAS, besides metallurgy, continued to deal with social questions. He already worked for 'Man' through agriculture, to which he gave the basic slag, but he didn't forget either his experience in the London law courts of his youth. Marked by the misery of his contemporaries, by the hardness of the worker's conditions, exposed to industrial diseases (in tanneries, manufacture of matches, etc). He was very conscious of the misdeeds of alcoholism and convinced about social idealism. He militated in favour of a system that would avoid the hereditary accumulation of richness, which was only destined to a chosen few. He also wished for an effective prevention against alcoholism, an encouragement for emigration to the United States (which was in full swing with the birth of the great American nation).

    Conscious that no law system can make a man virtuous, he recommended an improvement of public expenditure in regard to housing, education, the improvement of the State management of museums, parks, hospitals and schools. This was to be financed by the increase in the inheritance death taxes. According to him, the improvement of living conditions and the possibility of getting a suitable education, would begin a moral reform, that would be more fruitful than any law.

    Sidney THOMAS ended up in Paris, hoping for successful treatment. He was installed in a comfortable apartment, where he continued to assume the load of correspondence he had kept up with the owners of his processes. Various treatments were tried, but nothing worked, his disease progressed; this slow disease, which for years has been making him breathless and lose weight, this affection without a remedy which exhausted and destroyed him, killed relentlessly in this last quarter of the nineteenth century and was called tuberculosis. He died of it in his sleep on February first, 1885, at less than thirty-six years of age.

    Sidney THOMAS's heritage

    Between 1879 and 1882, from the initial patents of 1877, licenses were conceded with various metallurgists in England and on the continent. Now the exploitation of the phosphorous ores was possible during the thirty years that followed (in particularly those of the Lorraine layer and the phosphorous ores in Sweden, Wales, etc). The European production of steel was multiplied by 23 between 1880 and 1913; Non-existent in 1880, the contribution of the basic Bessemer steel was of 62% in 1913.

    The advent of the basic converter process into France, was the true starting of the industrial revolution, would be the object of an article to appear on the basic converter process itself. HENRI SCHNEIDER, in the Creusot, to whom THOMAS had taken the initiative to present his process as soon as the first casts succeeded, was the first to negotiate the process. Because of the specificity of its manufacturing method, the process was only of little interest to SCHNEIDER, so he proposed it to the WENDEL family, who were already in negotiation with THOMAS to negotiate the patent. In November 1879, THOMAS gave the use of the process to the association between WENDEL and SCHNEIDER, so as to exploit it in a newly built factory in Joeuf . The first basic converter heat in Joeuf happened at the beginning of 1883.

    (*) see papers to appear on the LWS process in "one century of oxygen in steelmaking" and "terms of Steel".

    The basic Bessemer converter proved to be a remarkably robust industrial process. It underwent only few modifications (blasting with oxygen-enriched air, or an oxygen-vapour mixture), which opened the way to its contemporary 'inheritors', the LWS and related processes (Q-bop, etc), with pure oxygen blowing in by the bottom through concentric nozzles, cooled by the vapour cracking of water (1968) or hydrocarbons (1970)(*).

    It was satisfactory to note that contrary to philanthropists of the time (for example the English painter J.M. William TURNER, 1775-1851), the spirit of Sidney THOMAS's testament was well defended by his family, and particularly by his sister Lillian, and so was not betrayed. Lillian THOMAS used the fortune from the patent to build living quarters in the industrial districts of London and to save buildings of historical or artistic interest. She founded a "Trust" which maintained a delegate with the court of justice where her brother had begun his career, charged with advising and assisting the more underprivileged in their legal steps. She also founded Tonybee Hall, an institution dedicated to: the fight against alcoholism, teaching and social reform.

    Sidney Gilchrist THOMAS's heritage, built in less than thirty-six years of life, was remarkably fruitful; even though his processes opened up the ways to innovations which make them seem obsolete today, his work changed the face of the metallurgical, industrial and agricultural world. It also showed the way of a modern not theoretical humanism because of its social aspects.


    ALLARD M., "Le procédé THOMAS dans le patrimoine français", La Revue de Métallurgie, volume XLVII, nĝ12, 1950.

    AURIAC (D') A., "Leçons de sidérurgie", DUNOD 1922.

    DESCH C.H., "la vie de S.G. THOMAS", La Revue de Métallurgie, volume XLVII, nĝ12, 1950.

    GALEY J. & Alii, "Mesure et enregistrement de la température du bain au convertisseur THOMAS par visée ... travers le bec", La Revue de Métallurgie, juillet 1959.

    LECOMPTE H., "Cours d'Aciérie", Editions de la Revue de Métallurgie, v. 1961.

    LEROY P., MAUBON A., BASTIEN J., "Soufflage d'oxygène pur par le procédé LWS", La Revue de Métallurgie, juin 1975.

    MOINE J-M., "Les Barons du Fer", (pp.56-60 for THOMAS process in Lorraine), Serpenoise, 1989.


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