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Minerals and Metals in Ancient India v1.c26.s2: Zinc Metal and High-Zinc Brass

Minerals and Metals in Ancient India v1.c26.s2

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Zinc Metal and High-Zinc Brass

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The earliest brass containing more than 28 per cent zinc, which could be made only after the isolation of pure zinc metal, came from Taxila. We have noted in our chapter 14 the overriding importance of the vase (BM 215-284) excavated from the Bhir Mound at Taxila and dated to the fourth century BC. This brass sample contains 34.34 per cent zinc, 4.25 Sn, 3.0 Pb, 1.77 Fe and 0.4 Nickel. This is very strong evidence for the availability of metallic zinc in the fourth century BC. (Craddock, 1981: 16-17) Most possibly India was the first to make this metal zinc (rasaka) by the distillation process as practised for the other metal mercury (rasa).

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There are references to zinc and brass in the lost fourth century BC text Philippica of Theopompus, quoted by Strabo in his Geography:

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There is a stone near Andreida (north-west Anatolia) which yields iron when burnt. After being treated in a furnace with a certain earth it yields droplets of false silver. This, added to copper, forms the so-called mixture, which some call oreichalkos. (Jones, 1968)

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The above reference is probably to the process of downward distillation of zinc (‘droplets of false silver’) and its subsequent mixing with copper to make brass oreichalkos (ārakūṭa in Kauṭilya’s Arthaśāstra) described in detail in the post-Christian era Sanskrit texts.

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It is quite possible that the zinc-making technology travelled west from India during sixth-fifth century BC, as it did later again in the eighteenth century AD. The pseudo-Aristotelian work On Marvellous Things Heard mentioned:

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They also say that amongst the Indians the bronze is so bright, clean and free from corrosion that it is indistinguishable from gold, but that amongst the cups of Darius there is a considerable number that could not be distinguished from gold or bronze except by colour. (quoted by Craddock, 1978: 8)

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The Indian emphasis was on the ‘gold-like’ brass and not on the zinc metal. The Greeks however used zinc metal as such in a few cases. In the course of the excavation of the Agora in Athens a roll of sheet zinc was found in a sealed deposit dating from the third or second century BC. (Farnsworth et al., 1949) Analysis showed it to be nearly pure zinc with 1.3 per cent lead, 0.06 Cd, 0.016 Fe, 0.005 Cu with traces of Mn, Mg, Sn, Ag, and Sb. A Hellenistic statuette, also from the Agora, but from a mixed deposit, has also been shown to contain more than 99 per cent zinc. (T. Wheeler quoted by Craddock, 1978: 7) Although Needham and Forbes doubted the above evidences on the ground that ‘the pieces were beyond the contemporary technology’ (Craddock, 1981: 18), it is quite possible that the Greeks had carried the material or the technology which had existed in Taxila as early as fourth century BC and possibly much earlier in Rajasthan.

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India’s monopoly on high zinc (more than 28 per cent) brass has never been questioned. The manufacture of zinc metal by reduction and distillation was a well-guarded Indian secret. The Western countries knew about the cementation route for making low-zinc brass, but after Theopompus referring to ‘droplets of false silver’, the art of making zinc and high-zinc brass was almost unknown in the West till the early part of the eighteenth century when the knowledge again travelled from India, and William Champion of Bristol, England utilised it to manufacture the said materials.

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