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Introduction to the archaeometallurgy of iron
Donald B. Wagner

Direct iron smelting in South Asia

Bloomery smelting was practised in most parts of India and surrounding lands until the early 19th century. The various traditional iron industries were observed and described by many English colonial officers, and as usual we see a great variation in the techniques used.

A bibliography of references on traditional Indian iron smelting is here.

For the moment I shall limit discussion to a technique practised in the Khasi Hills in what is now Meghalaya State in northeastern India. It was described by W. Cracroft (1832) and by Joseph Dalton Hooker (1855, vol. 2: 304–307). Both descriptions are discussed by John Percy (1864: 262–265). These authors give the sketches reproduced below. Other, very brief, descriptions are by Yule (1832) and Walters (1832).

The ore here is ironsand, sluiced from river sand. Ironsand was much used in China, and I have written briefly about it here. (Chinese translation here.)

The ‘furnace’ is a shallow hearth. The smelting reactions take place at ground level, and what in Cracroft’s sketch appears to be a furnace shaft is in fact merely a chimney, carrying waste gases away from the operator and towards the hole in the roof. It may also strengthen the blast by the ‘chimney effect’.

The blast appears to enter the hearth at the bottom. In Cracroft’s sketch, the operator works the bellows by swinging his body left and right, meanwhile continuously feeding the hearth with a mixture of damp charcoal and ironsand from the trough, no. 9 in the sketch. ‘When a mass of [smelted] iron is formed on the hearth, it is taken out with tongs, and beaten with a heavy wooden mallet on a large stone by way of anvil. The iron in this state is sent down to the plains for sale or barter.’

The two descriptions that we have of this process are very brief, and it is difficult to say very much about how it works. One thing is clear: it required long experience and great skill on the part of the operator. He had to watch the fire closely and continuously adjust the blast and the feeding of the hearth very precisely in order to build up particles of iron reduced from the ironsand to a bloom without the iron being oxidized again. Ironsand is a very rich ore, often with less than 10% gangue, so the process may not have produced much slag, which is usually necessary to protect the iron from being oxidized.

Sketch of a bloomery ironworks in the Khasi Hills, Meghalaya State, India (Cracroft 1832, pl. 6).

1. The chimney of the furnace supported by stone pillars, so as not to touch the hearth. 2. One pair of bellows open. 3. One pair of bellows shut. 4. Frame on which the man rests. 5. A primitive ladder for mounting the bellows. 6. The wooden mallet. 7. The tongs. 8. The spoon. 9. The trough supported by a wooden fork.

Sketch of a similar ironworks in the Khasi Hills (Hooker 1855, vol. 2: 306; Percy 1864: 264).

Another sketch (Walters 1832)

References

Cracroft, W. 1832. ‘Smelting of iron in the Kasya Hills’. Journal of the Asiatic Society of Bengal 1: 150–151 + pl. 6. archive.org/details/journalasiatics01benggoog

Hooker, Joseph Dalton. 1855. Himalayan journals: Notes of a naturalist in Bengal, the Sikkim and Nepal Himalayas, the Khasia Mountains, &c. 2 vols. London: John Murray. ‘New edition, carefully revised and condensed.’ archive.org/details/himalayanjourna00hookgoog

Percy, John. 1864. Metallurgy . . . [Vol. 2:] Iron; steel. London: John Murray. archive.org/details/metallurgyartex02percgoog

Walters, H. 1832. ‘Journey across the Pandua Hills, near Silhet, in Bengal’. Asiatic researches 17: 499–512. Sketch of iron-smelting furnace, plate XVI, between pp. 502–503. Brief mention, p. 505. biodiversitylibrary.org/page/42253341

Yule, H. 1832. ‘Notes on the Iron of the Kasia Hills, for the Museum of Economic Geology’. Journal of the Asiatic Society of Bengal 11: 853–857. archive.org/details/journalofasiatic112asia/page/852/mode/2up

Last edited by DBW 28 February 2023