Long Read: How India’s Metallurgical Tradition Represents Continuity Between Geographies And Time 

Long Read: How India’s Metallurgical Tradition Represents Continuity Between Geographies And Time An Indus citadel
Snapshot
  • What the Keezhadi excavations mean and don’t.

Alexander’s soldiers had heard of the fantastic steel swords that could cut through fine gauze, which Darius, the Emperor of Persia, had received as a gift from India over couple of millennia ago, and of the fabulous amounts of gold dust he had received in tribute from his Indian satrap.

But nothing prepared them for the wonders they saw in Taxila. They had mistaken the giant statues and vessels as being of gold, only to be told they were brass. And they were horrified when they found that the bronze vessels they dropped by mistake broke instead of getting dented, only to be reassured by the strange people of the Indus that the metalsmiths would cast them back from the fragments again.

Cast? Weren’t they hammered from sheets like everywhere else? The Indians were bemused in return: how could the Greeks even think of using ordinary bronze and copper vessels for holding food? Didn’t they know it would poison them?

Tin Bronzes, And High-Tin Bronzes

Bronze containing up to 16 per cent tin in copper is in the form of a solid solution, a physical mixture — like sugar in water — except that it is solid. If the content of tin were increased further, up to around 23 per cent, the copper (chemical symbol, Cu) and tin (Sn) would form what is known as an intermetallic compound, with the formula, Cu5Sn.

This is known as beta- (β-) bronze. It forms at a high temperature, and can only be retained by quenching, or rapidly cooling (a process called quenching) from the high temperature at which it is cast, to prevent the formation of other, unwanted forms of bronze.

The solid solution form, as you may have guessed, is called alpha- (α-) bronze. The problem with β-bronzes, though, is that they are brittle at room temperature (which explains why they broke upon impact).

The way around this is to heat it back up to between 600-750°C, where it is plastic (i.e. like a putty, although a very hard one) rather than brittle, and shape it by hammering. In other words, β-bronze vessels were cast and wrought.

As it is a compound (where the atoms are held together by strong chemical bonds), the copper does not dissolve into the food placed in a β-bronze vessel, and there is no danger of copper poisoning, even if you use the vessel to hold yogurt. For metalsmiths, the recipe is easy to remember: two parts of tin and seven of copper.

The earliest known instance of β-bronzes may go back to Mohenjodaro in the Indus Valley Civilisation. Fragments of bronze containing 23 per cent or more of tin were found at multiple levels at this site, the oldest of them going back to the late fourth millennium BCE.

Barring stray instances of objects which may have been obtained by trade, the earliest appearance of tin-bronzes outside the Indian subcontinent is only from the mid-third millennium BCE.

The discovery that tin could be alloyed with copper to produce bronze, which had significantly better mechanical properties than copper, ushered in a revolution in the prehistoric world.

It appears that the Indus civilisation was not only the earliest to discover tin-bronze technology for producing stronger and tougher alloys but had also gone much further in exploring different types of bronzes and their uses.

Many plates, cups and vessels ranging from the prehistoric to the historic period found at different sites in Balochistan were also found to have 23 per cent tin or more, the fact that they were all meant for holding food quite clearly being the reason behind their composition. Many β-bronze objects were also found in the Gandharan Grave Culture (early first millennium BCE).

Corroborating the accounts of Alexander’s Greeks, a large number of β-bronze objects were found in the Bhir mound at Taxila, dating from the fourth century BCE to the second century CE. The tradition of making β-bronzes has obviously had an unbroken continuity to the present day in this region, as they are still made there.

The technology spread to other parts of India too, with β-bronzes being reported from the early historic period in Bengal. Many Chola plates from the 10th-11th centuries were also found upon analysis to be β-bronzes.

As may be known to some readers, there are a small — and unfortunately dwindling — number of traditional workshops in places such as Pazhayangadi (also known as Payangadi) in Kerala and Nacharkoil and Swamimalai in Tamil Nadu that even today manufacture these traditional bronze vessels, alongside other artefacts such as temple bells and mūrtis.

Bronzes containing an even higher proportion of tin — 32.6 per cent to be precise — are also special in a very different way. At this composition, copper and tin form the intermetallic compound, Cu31Sn8, which is also called the δ-phase.

This bronze can be polished to an exceptional degree of reflectance, and can be used as a mirror. Bronze mirrors are not unique to India. They have been used in Egypt, China, Mesopotamia and Rome.

But they invariably use high amounts of lead to make them easier to cast, which also leads to a duller appearance and some loss in reflectance. They were also much thicker than Indian mirrors.

To overcome the problem of brittleness, Indian bronze mirrors were cast as very thin discs, which were then stuck to a wooden block and polished. The finished mirror was traditionally left on the wooden block, with a handle provided at the back, as this image of a damsel from the Chennakesava Temple in Belur, Karnataka illustrates.

High-tin bronze mirrors too were historically made in many parts of India. The Harappans, who, thanks to the scarcity of tin on the Indian subcontinent, never left metal objects in graves and scrupulously recycled virtually all their metal objects and jewellery, made an exception for mirrors.

However, the Harappan mirrors are so heavily corroded that analysis is not possible. Nevertheless, the fact that the mirrors appeared to be very thin, in the style of later ones, suggests that Indian bronze mirror-making goes all the way back to the Indus civilisation.

Indian bronze mirrors were found in the graves of Scythians, Sarmatians and other nomadic tribes of Central Asia and the Urals dating back to the sixth century BCE, suggesting that the Indus civilisation had a rather large and enduring cultural footprint.

Many such mirrors were found in Taxila too, with the innovation that they were provided with long ivory or wooden handles, giving them the appearance of rattles.

Today, this technology survives in very few places in India, such as Aranmula in Kerala. Till recently, high-tin bronze mirrors like the famed Aranmula Kannadi were used exclusively in the traditional Ṣoḍaśopacāra Pūjā, and are preferred over glass mirrors by many even today for ritual purposes.

What is interesting is how — and how early — the copper and bronze technology of the Harappans reached Peninsular and South India. The received wisdom is that the Harappans — or at least some of them — moved to the south after the “collapse” of their civilisation, and the immigrating Aryans from the Steppe turfed them out. The truth, as we shall find out, is more complex.

When The Peninsular Chalcolithic Sprang A Surprise

In 1954, when B.K. Thapar excavated the site of Maski in Karnataka, he had provisionally dated the Chalcolithic levels at this site to 1000-400 BCE.

However, a couple of years later, at Piklihal in Raichur district, F.R. Allchin found a copper chisel very similar to those in Indus Valley sites. Some ceramic “offering stands” found here too seemed unique for the region, with the exception of one such stand from Maski, and strikingly similar to Indus ones.

When the radiocarbon dates for Maski were eventually reported, they confirmed Allchin’s hunch — the dates were in the range 3000-1200 BCE, much earlier than those originally proposed by Thapar.

Then came the discovery that the signature Indus crops, barley and wheat, were also briefly grown in Karnataka in 1900-1800 BCE, which is practically the closing years of the urban phase of the Indus civilisation, although the unsuitable warmer climate in the south put a stop to this very quickly. Around this time, the Harappans also introduced cotton to the Deccan.

The North And The South

Clearly, deep ties existed between the Indus region and South India from at least the third millennium BCE, if not much earlier. It is possible that the Indus people may have been obtaining some of their gold from Karnataka.

Karnataka also has deposits of copper, including in Raichur district. The precondition for exploiting copper deposits is that they should be identified, and the ore smelted. The Indus people had ample reserves of copper ore in Balochistan, Rajasthan and Gujarat and were familiar with copper technology.

They may have been responsible for the advent of the Chalcolithic age in Peninsular India — they would have known how to identify copper orebodies, from characteristics such as a visible encrustation of green malachite produced by the oxidation of the copper ore on the surface, and they would have had the know-how to dress and roast the ore, and smelt copper from it.

It is in this way that the Harappan bronze technology, including knowledge of high-tin bronzes, arrived on the Peninsula and in the South. Vessels of β-bronze from the very early first millennium BCE are known from megalithic sites in Vidarbha, the Nilgiri Cairns and the site of Adichanallur in Thoothukudi district of Tamil Nadu.

In the late nineteenth century, Breeks had reported that many tribal communities of the Nilgiris like the Todas had fine high-tin bronze vessels for ritual use in their possession, that were handed down generations, and supplemented by fresh purchases from markets in the Malabar.

As early as 1941, Paramasivan had analysed the microstructure of the bronze bowl from Adichanallur, and found it to be of β-bronze, although it was not clear at the time how this technology had come to be there.

But if you are inclined to think this flow of knowledge was one-way, think again: The South played a major role in the development of iron and steel technology, where the Indus region was at a natural disadvantage in not having conspicuous reserves of iron ore.

For very long, it has been assumed that India’s Iron Age was begun by Aryan immigrants from outside the subcontinent, who progressed to the use of iron after settling down in the north after around 1300 BCE.

However, we now know that iron smelting was widespread not just in the Ganga plain but also many places in the South by the earliest second millennium BCE.

But the smelting of iron itself would not have been very helpful, as the iron would have been not much harder than the copper the Indians were already familiar with.

It was not until the carburization of iron was mastered that it was possible to make hard iron that could be put to widespread use and supersede bronze for some applications at least.

Ancient blacksmiths would carburize thin sheets of iron, and join them together at the edges by hammering. This practice of piling carburized sheets of iron to make large objects is known as lamination, and represented a huge technological breakthrough.

The earliest evidence of lamination in the world is from around 1200 BCE from the megalithic site of Tadakanhalli in Karnataka. By this time, the blacksmiths of Tadakanhalli were masters at making large objects like spears, axes and knives by lamination, implying that they had been experimenting with the technique for many centuries by then.

This technique quickly spread all over the subcontinent, with many examples of objects produced by lamination from the Ganga plain by the early first millennium BCE.

Till the discovery of tempering and quenching, and the production of steels, the technique of lamination was the mainstay for making iron objects.

Unity From Four Thousand Years Ago?

The extensive interaction between the Indus region, the Ganga plain and the South highlights a striking fact: the remarkable sense of unity between the various regions of the subcontinent from over 4,000 years ago.

The Indus people were involved in extensive trade for millennia with adjacent Iran, Central Asia and Mesopotamia, but for exchange of knowledge and technology they preferred to look to other regions of the subcontinent.

To give just one example, the know-how for making high-tin bronzes does not appear to have been shared with these regions: analysis of bronze objects from these cultures shows that they were limited to simple α-bronzes.

Similarly, the Indus people, who may have been the first to make brass by alloying copper with zinc, and the later cultures of the subcontinent which perfected this technology, preferred not to disclose the knowledge of this highly useful alloy to others.

Even our neighbours, the ancient Persians, were astounded by this exotic alloy, which looked like gold but was suitable for mundane use. Till William Champion reverse-engineered the traditional Indian process for the production of metallic zinc in the eighteenth century, Europe was largely dependent on costly zinc ingots imported from India for making brasses.

This was even as brass was being used extensively all over the subcontinent for making everything from inexpensive household pots and pans to gigantic statues and even Buddhist Viharas, despite zinc deposits in India being overwhelmingly confined to present-day Rajasthan.

It is hard to miss this strong cultural unity that has pervaded the subcontinent for millennia.

As an aside, the tight-lipped approach of the Indians to foreigners was not without a sense of humour. Darius of Persia had wanted to know from the Indians where they had obtained such a large amount of gold.

He was told that it had been dug up by ants in the desert on the other side of the Indus (Native or placer gold is often in the form of small nuggets or even dust). The Greeks, who heard this from the Persians, had promptly embarked on an exploration of the western Thar as soon as they were able to, and were mighty disappointed when they found nothing but sand there.

They concluded, without realising the irony, that the Indians had no knowledge of gold-mining. Native gold dust was historically referred to as pipīlikā (“ant-gold”) including in the Mahabharata (2.54.4), and Indians obtained good quantities of it from the alluvial deposits in the Amu Darya region and Tibet.

The joke and subterfuge were very successful, for as late as 1838, Alexander von Humboldt wrote in his Essay on the Fluctuations in the Supplies of Gold, “The old Indian mythologists make the ruler of the north (Kuwera) the god of riches also; and it is remarkable enough that the residence of this deity (Alakā) must be sought for, not on the Himalaya itself, but on the Kailāsa, beyond the Himalaya, in Thibet. …the great golden sand deserts, visited by the Indians bordering on Kaschmir; and containing ‘ants less than dogs, but larger than foxes.’”

Nevertheless, starting from the historic period, and especially from the sixth century CE onwards, when Indian cultural influences in South-East Asia began, some of this knowledge made its way there and probably as far as Japan.

South Indians, Descendants Of The Harappans?

In the last month, there have been some articles reporting that archaeological excavations at the site of Keezhadi in Tamil Nadu have provided evidence that South Indian cultures were descended from the Harappan, which therefore, proves that the Harappans were Dravidian-speakers.

Such simplistic, even silly, theories adopt an ostrich-like approach to the obvious and voluminous evidence of continuity in the Indus region itself.

As described above, the high-tin bronze technology of the Harappans thrived through the second and first millennia BCE, and continues in the region to this day, even as it spread to other parts of the subcontinent.

Similarly, the early experiments of the Harappans in brass-making underwent refinement, with the metallurgists of the northwest eventually isolating metallic zinc, which enabled the production of brasses of precisely controlled compositions and properties.

At the same time, the Indus region, the Ganga plain, the Vindhyas, the Peninsula and South India, and even the Chalcolithic cultures of Bengal and Odisha were involved in an exchange of innovation and knowledge, which completely transformed the subcontinent, laying the ground for the historic period.

Ignoring facts or twisting them to fit preconceived theories is the preferred method for those with doctrinal axes to grind to trot out their theories. Such half-baked theories also fail to do justice to the distinct role and remarkable contributions of each region.

If the Harappans were pushed south, who were the people who were able to seamlessly continue the bronze and brass technology in the region, which would have required an intimate knowledge of the ores available there and their processing?

If the descendants of the evicted Harappans were the authors of sites like Keezhadi, then who were the people of the South, who were smelting iron by the early second millennium BCE and had mastered carburization by 1200 BCE, a technology the contemporary Indus region itself does not appear to have much knowledge of?

And if a bunch of foreign immigrants who entered the subcontinent after 1300 BCE had started India’s Iron Age in the Punjab-Haryana region, who were the people of Eastern Uttar Pradesh, Bihar and the Vindhya region who had become adept at smelting large amounts of iron by 1,800 BCE?

The metallurgical tradition of the Indian subcontinent is not only the result of unbroken continuity from the earliest developments in the Indus Valley region but also exemplifies a strong, unmistakable thread of unity between the various regions of the subcontinent for at least the last four millennia.

In that sense, the traditional bronze- and brass-making workshops in many parts of the country are the direct inheritors of the legacy of the Indus civilisation.

However, the Ganga Plain, Central, Peninsular and South India also had their own distinct contributions to this tradition, especially in ferrous metallurgy.

I have previously pointed out that the telling of India’s history has been hijacked by the ideologically prejudiced, who, with great sophistication, put forth entirely baseless speculation as respectable scholarship, which then, by force of repetition, acquires the status of established fact.

A prime example of this is the alleged Aryan-Dravidian divide.

Fortunately, however, reconstructing the past is becoming an increasingly interdisciplinary exercise, with scientific analyses coming to the forefront. Although the old order — which has shown neither the capacity nor inclination for acquiring the necessary interdisciplinary skills — continues to have a stranglehold on India’s historical narrative, hopefully the scientific evidence from multiple disciplines will soon call their bluff.

Anil Kumar is a materials scientist.

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