Iron and Steel - Dharampal’s comments on Indian steel

Excerpts from Dharampalji's book Indian Science and Technology in the 18th Century (1971)

The substance which seems to have evoked most scientific and technical interest in the Britain of the 1790s was the sample of wootz steel sent by Dr. Scott to Sir J. Banks, the President of the British Royal Society. The same went through examination and analysis by several experts (Mushet, Pearson, 1795). It was found in general to match the best steel then available in Britain, and according to one user, "promises to be of importance to the manufactures of Britain (Heyne, 1814). He found it "excellently adapted for the purpose of fine cutlery, and particularly for all edge instruments used for surgical purposes". After its being sent as a sample in 1794 and its examination and analysis in late 1794 and early 1795, it began to be much in demand; and some 18 years later the afore quoted user of
steel stated, "I have at this time a liberal supply of Wootz, and I intend to use it for many purposes. If a better steel is offered to me, I will gladly attend to it; but the steel of India is decidedly the best I Have yet met with" (Heyne, 1814).

Whatever may have been the understanding in the other European countries regarding details of the processes employed in the manufacture of Indian steel, the British, at the time wootz was examined and analysed by them, concluded "that it is made directly from the ore; and consequently that it has never been in the state of wrought iron" (Pearson, 1795). Its qualities were thus ascribed to the quality of the ore from which it came and these equalities were considered to have little to do with the techniques and processes employed by the Indian manufacturers. In fact it was felt that the various cakes of wootz were of uneven texture and the cause of such imperfection and defects was thoughts to lie in the crudeness of the techniques employed.

It was only some three decades later that this view was revised. An earlier version in fact, even when confronted with contrary evidence as was made available by other observers in the Indian techniques and processes, was an intellectual impossibility. "That iron could be converted into cast steel by fusing it in a closed vessel in contact with carbon" was yet to be discovered, and it was only in 1825 that a British manufacturer "took out a patent for converting iron into steel by exposing it to the action of carburreted hydrogen gas in a closed vessel, at a very high temperature, by which means the process of conversion is completed in a few hours, while by the old method, it was the work of from 14 to 20 days" (Heath, cited in Mushet).

According to J. M. Heath, founder of the Indian Iron and Steel Company, and later prominently associated with the development of steel making in Sheffield, the Indian process appear to combine both of the above early 19th century British discoveries. He observed: "Now it appears to me that the Indian process combines the principles of both the above desired methods. On elevating the temperature of the crucible containing pure iron, and dry wood, and green leafs, an abundant evolution of carburreted hydrogen gas would take place from the vegetable matter, and as its escape would be prevented by the luting at the mouth of the crucible, it would be retained in contact with the iron, which, at a high temperature, appears (from the above-mentioned patent process) to have a much greater affinity for gaseous then for concrete carbon; this would greatly shorten the operation and probably yet a much lower temperature then were the iron in contact with charcoal powder." (Cited in Mushet)

And he added: "In no other way can I account for the fact that iron is converted into cast steel by the natives of India, in 2 hours and a half, with an application of heat, that, in this country, would be considered quite inadequate to produce such an effect; while at Sheffield it requires at least four 4 hours to melt blistered steel in wind-furnaces of the best construction, although the crucibles in which the steel is melted are at a white heat when the material is put into them, and in the Indian process, the crucibles are put into the furnace quite cold".

The above quoted British authority however did not imply that the Indian practice was based on a knowledge "of the theory of his operations" by the Indian manufacturer. He felt it to be impossible "that the process was discovered by any scientific induction, for the theory of it can only be explained by the lights of modern chemistry".

By K. Kesava Rao
Department of Chemical Engineering
Indian Institute of Science
Bengaluru 560012, India
kesava@iisc.ac.in

...To be continued ...

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