History of metallurgy in the Indian subcontinent
History of metallurgy in the Indian subcontinent began during the 2nd millennium BCE and continued well into the British Raj. Metals and related concepts were mentioned in various early Vedic age texts. The Rigveda already uses the Sanskrit term Ayas (metal). The Indian cultural and commercial contacts with the Near East and the Greco-Roman world enabled an exchange of metallurgic sciences. With the advent of the Mughals, India's Mughal Empire (established: April 21, 1526—ended: September 21, 1857) further improved the established tradition of metallurgy and metal working in India.
The imperial policies of the British Raj led to stagnation of metallurgy in India as the British regulated mining and metallurgy—used in India previously by its rulers to build armies and resist England during various wars.
Recent excavations in Middle Ganga Valley done by archaeologist Rakesh Tewari show iron working in India may have begun as early as 1800 BCE. Archaeological sites in India, such as Malhar, Dadupur, Raja Nala Ka Tila and Lahuradewa in the state of Uttar Pradesh show iron implements in the period between 1800 BCE - 1200 BCE. Sahi (1979: 366) concluded that by the early 13th century BCE, iron smelting was definitely practiced on a bigger scale in India, suggesting that the date the technology's inception may well be placed as early as the 16th century BCE.
The Black and Red Ware culture was another early Iron Age archaeological culture of the northern Indian subcontinent. It is dated to roughly the 12th – 9th centuries BCE, and associated with the post-Rigvedic Vedic civilization. It reached from the upper Gangetic plain in Uttar Pradesh to the eastern Vindhya range and West Bengal.
Perhaps as early as 300 BCE, although certainly by 200 CE, high quality steel was being produced in southern India by what Europeans would later call the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in crucibles and heated until the iron melted and absorbed the carbon. The resulting high-carbon steel, called fūlāḏ فولاذ in Arabic and wootz by later Europeans, was exported throughout much of Asia and Europe.
"Something has been said about the chemical excellence of cast iron in ancient India, and about the high industrial development of the Gupta times, when India was looked to, even by Imperial Rome, as the most skilled of the nations in such chemical industries as dyeing, tanning, soap-making, glass and cement... By the sixth century the Hindus were far ahead of Europe in industrial chemistry; they were masters of calcinations, distillation, sublimation, steaming, fixation, the production of light without heat, the mixing of anesthetic and soporific powders, and the preparation of metallic salts, compounds and alloys. The tempering of steel was brought in ancient India to a perfection unknown in Europe till our own times; King Porus is said to have selected, as a specially valuable gift from Alexander, not gold or silver, but thirty pounds of steel. The Moslems took much of this Hindu chemical science and industry to the Near East and Europe; the secret of manufacturing "Damascus" blades, for example, was taken by the Arabs from the Persians, and by the Persians from India."
Hindu, Buddhist, Jain and other texts 
The references to Ayas in the Rig Veda probably refer to bronze or copper rather than to iron. However, D. K. Chakrabarti (1992) argued: "It should be clear that any controversy regarding the meaning of ayas in the Rgveda or the problem of the Rgvedic familiarity or unfamiliarity with iron is pointless. There is no positive evidence either way. It can mean both copper-bronze and iron and, strictly on the basis of the contexts, there is no reason to choose between the two."
The Arthasastra lays down the role of the Director of Metals, the Director of Forest Produce and the Director of Mining. It is the duty of the Director of Metals to establish factories for different metals. The Director of Mines is responsible for the inspection of mines. The Arthasastra also refers to counterfeit coins.
Other texts 
There are many references to Ayas in the early Indian texts.
The Atharva Veda and the Satapatha Brahmana refer to krsna ayas ("black metal"), which could be iron (but possibly also iron ore and iron items not made of smelted iron). There is also some controversy if the term syamayas ("black metal) refers to iron or not. In later texts the term refers to iron. In earlier texts, it could possibly also refer to darker-than-copper bronze, an alloy of copper and tin. Copper can also become black by heating it. Oxidation with the use of sulphides can produce the same effect.
The Yajurveda seems to know iron. In the Taittiriya Samhita are references to ayas and at least one reference to smiths. The Satapatha Brahmana 188.8.131.52 refers to the smelting of metallic ore. In the Manu Smriti (6.71), the following analogy is found: "For as the impurities of metallic ores, melted in the blast (of a furnace), are consumed, even so the taints of the organs are destroyed through the suppression of the breath." Metal was also used in agriculture, and the Buddhist text Suttanipata has the following analogy: "for as a ploughshare that has got hot during the day when thrown into the water splashes, hisses and smokes in volumes..."
In the Charaka Samhita an analogy occurs that probably refers to the lost wax technique. The Silpasastras (the Manasara, the Manasollasa (Abhilashitartha-Chintamani[disambiguation needed]) and the Uttarabhaga of Silparatna) describe the lost wax technique in detail.
An influential Indian metallurgist and alchemist was Nagarjuna (born 931). He wrote the treatise Rasaratnakara that deals with preparations of rasa (mercury) compounds. It gives a survey of the status of metallurgy and alchemy in the land. Extraction of metals such as silver, gold, tin and copper from their ores and their purification were also mentioned in the treatise. The Rasa Ratnasamuccaya describes the extraction and use of copper.
Chakrabarti (1976) has identified six early iron-using centres in India: Baluchistan, the Northwest, the Indo-Gangetic divide and the upper Gangetic valley, eastern India, Malwa and Berar in central India and the megalithic south India. The central Indian region seems to be the earliest iron-using centre.
The earliest evidence for smelted iron in India dates to 1300 to 1000 BCE. These early findings also occur in places like the Deccan and the earliest evidence for smelted iron occurs in Central India, not in north-western India. Moreover, the dates for iron in India are not later than in those of Central Asia, and according to some scholars (e.g. Koshelenko 1986) the dates for smelted iron may actually be earlier in India than in Central Asia and Iran. The Iron Age did however not necessary imply a major social transformation, and Gregory Possehl wrote that "the Iron Age is more of a continuation of the past then a break with it".
Archaeological data suggests that India was a "an independent and early centre of iron technology." According to Shaffer, the "nature and context of the iron objects involved [of the BRW culture] are very different from early iron objects found in Southwest Asia." In Central Asia, the development of iron technology was not necessarily connected with Indo-Iranian migrations either.
J.M. Kenoyer (1995) also remarks that there is a "long break in tin acquisition" necessary for the production of "tin bronzes" in the Indus Valley region, suggesting a lack of contact with Baluchistan and northern Afghanistan, or the lack of migrants from the north-west who could have procured tin.
Indus Valley Civilization 
The copper-bronze metallurgy in the Harappan civilization was widespread and had a high variety and quality. The early use of iron may have developed from the practice of copper-smelting. While there is to date no proven evidence for smelted iron in the Indus Valley Civilization, iron ore and iron items have been unearthed in eight Indus Valley sites, some of them dating to before 2600 BCE. There remains the possibility that some of these items were made of smelted iron, and the term "krsna ayas" might possibly also refer to these iron items, even if they are not made of smelted iron.
Lothali copper is unusually pure, lacking the arsenic typically used by coppersmiths across the rest of the Indus valley. Workers mixed tin with copper for the manufacture of celts, arrowheads, fishhooks, chisels, bangles, rings, drills and spearheads, although weapon manufacturing was minor. They also employed advanced metallurgy in following the cire perdue technique of casting, and used more than one-piece moulds for casting birds and animals. They also invented new tools such as curved saws and twisted drills unknown to other civilizations at the time.
Copper and its alloys were also used to create copper-bronze images such as Buddhas or Hindu/Mahayana Buddhist deities. Hiuen Tsang also noted that there were copper-bronze Buddha images in Magadha. In Varanasi, each stage of the image manufacturing process is handled by a specialist.
One of the most important sources of history in the Indian subcontinent are the royal records of grants engraved on copper-plate grants (tamra-shasan or tamra-patra). Because copper does not rust or decay, they can survive indefinitely. Collections of archaeological texts from the copper-plates and rock-inscriptions have been compiled and published by the Archaeological Survey of India during the past century. The earliest known copper-plate known as the Sohgaura copper-plate is a Maurya record that mentions famine relief efforts. It is one of the very few pre-Ashoka Brahmi inscriptions in India.
Gold and silver 
In the 5th century BCE, the Greek historian Herodotus observed that "Indian and the Persian army used arrows tipped with iron." Ancient Romans used armour and cutlery made of Indian iron. Pliny the Elder also mentioned Indian iron. Muhammad al-Idrisi wrote the Hindus excelled in the manufacture of iron, and that it would be impossible to find anything to surpass the edge from Hindwani steel. Quintus Curtius wrote about an Indian present of steel to Alexander. Ferrum indicum appeared in the list of articles subject to duty under Marcus Aurelius and Commodus. Indian Wootz steel was held in high regard in Europe, and Indian iron was often considered to be the best.
Wootz and steel 
The first form of crucible steel was wootz, developed in India some time around 300 BCE. In its production the iron was mixed with glass and then slowly heated and then cooled. As the mixture cooled the glass would bond to impurities in the steel and then float to the surface, leaving the steel considerably more pure. Carbon could enter the iron by diffusing in through the porous walls of the crucibles. Carbon dioxide would not react with the iron, but the small amounts of carbon monoxide could, adding carbon to the mix with some level of control. Wootz was widely exported throughout the Middle East, where it was combined with a local production technique around 1000 CE to produce Damascus steel, famed throughout the world. Wootz derives from the Kannada term for steel ukku. Indian wootz steel was the first high quality steel that was produced.
Henry Yule quoted the 12th century Arab Edrizi who wrote: "The Hindus excel in the manufacture of iron, and in the preparations of those ingredients along with which it is fused to obtain that kind of soft iron which is usually styled Indian steel (Hindiah). They also have workshops wherein are forged the most famous sabres in the world. ...It is not possible to find anything to surpass the edge that you get from Indian steel (al-hadid al-Hindi).
As early as the 17th century, Europeans knew of India's ability to make crucible steel from reports brought back by travelers who had observed the process at several places in southern India. Several attempts were made to import the process, but failed because the exact technique remained a mystery. Studies of wootz were made in an attempt to understand its secrets, including a major effort by the famous scientist, Michael Faraday, son of a blacksmith. Working with a local cutlery manufacturer he wrongly concluded that it was the addition of aluminium oxide and silica from the glass that gave wootz its unique properties.
Earliest evidence of steel making comes to us from Samanalawewa area in Sri Lanka where thousands of sites were found. These early furnaces were powered by Monsoon winds and has been dated to 300 BCE using radiocarbon dating techniques. The crucible steel making industry in Sri Lanka was already in decline around 1900 CE, but the historian and philosopher Ananda Coomaraswamy could still find two old Sri Lankians who could demonstrate the crucible steel making process to him.
After the Indian rebellion of 1857, many Indian wootz steel swords were destroyed by order of the British authorities. Metal working suffered a decline during the British Empire, but steel production was revived in India by Jamsetji Tata.
Zinc was extracted in India as early as in the 4th to 3th century BCE. Zinc production may have begun in India, and ancient northwestern India is the earliest known civilization that produced zinc on an industrial scale. The distillation technique was developed around 1200 CE at Zawar in Rajasthan.
In the 17th century, China exported Zinc to Europe under the name of totamu or tutenag. The term tutenag may derive from the South Indian term Tutthanagaa (zinc). In 1597, Libavius, a metallurgist in England received some quantity of Zinc metal and named it as Indian/Malabar lead. In 1738, William Champion is credited with patenting in Britain a process to extract zinc from calamine in a smelter, a technology that bore a strong resemblance to and was probably inspired by the process used in the Zawar zinc mines in Rajasthan. His first patent was rejected by the patent court on grounds of plagiarising the technology common in India. However, he was granted the patent on his second submission of patent approval. Postlewayt's Universal Dictionary of 1751 still wasn't aware of how Zinc was produced.
The Arthasastra describes the production of zinc. The Rasaratnakara by Nagarjuna describes the production of brass and zinc. There are references of medicinal uses of zinc in the Charaka Samhita (300 BCE). The Rasaratna Samuchaya (800 CE) explains the existence of two types of ores for zinc metal, one of which is ideal for metal extraction while the other is used for medicinal purpose. It also describes two methods of zinc distillation.
Early History (—200 CE) 
Recent excavations in Middle Ganges Valley conducted by archaeologist Rakesh Tewari show iron working in India may have begun as early as 1800 BCE. Archaeological sites in India, such as Malhar, Dadupur, Raja Nala Ka Tila and Lahuradewa in the state of Uttar Pradesh show iron implements in the period between 1800 BCE-1200 BCE. Sahi (1979: 366) concluded that by the early 13th century BCE, iron smelting was definitely practiced on a bigger scale in India, suggesting that the date the technology's early period may well be placed as early as the 16th century BCE.
Some of the early iron objects found in India are dated to 1400 BCE by employing the method of radio carbon dating. Spikes, knives, daggers, arrow-heads, bowls, spoons, saucepans, axes, chisels, tongs, door fittings etc. ranging from 600 BCE—200 BCE have been discovered from several archaeological sites. In Southern India (present day Mysore) iron appeared as early as 11th century BCE—12th century BCE. These developments were too early for any significant close contact with the northwest of the country.
The earliest available Bronze age swords of copper discovered from the Harappan sites in Pakistan date back to 2300 BCE. Swords have been recovered in archaeological findings throughout the Ganges-Jamuna Doab region of India, consisting of bronze but more commonly copper. Diverse specimens have been discovered in Fatehgarh, where there are several varieties of hilt. These swords have been variously dated to periods between 1700-1400 BCE, but were probably used more extensively during the opening centuries of the 1st millennium BCE.
The beginning of the 1st millennium BCE saw extensive developments in iron metallurgy in India. Technological advancement and mastery of iron metallurgy was achieved during this period of peaceful settlements. The years between 322—185 BCE saw several advancements being made to the technology involved in metallurgy during the politically stable Maurya period (322—185 BCE). Greek historian Herodotus (431—425 BCE) wrote the first western account of the use of iron in India.
Perhaps as early as 300 BCE—although certainly by 200 CE—high quality steel was being produced in southern India by what Europeans would later call the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in a crucible and heated until the iron melted and absorbed the carbon. The first crucible steel was the wootz steel that originated in India before the beginning of the common era. Wootz steel was widely exported and traded throughout ancient Europe, China, the Arab world, and became particularly famous in the Middle East, where it became known as Damascus steel. Archaeological evidence suggests that this manufacturing process was already in existence in South India well before the Christian era.
Zinc mines of Zawar, near Udaipur, Rajasthan, were active during 400 BCE. There are references of medicinal uses of zinc in the Charaka Samhita (300 BCE). The Rasaratna Samuccaya (800 CE) explains the existence of two types of ores for zinc metal, one of which is ideal for metal extraction while the other is used for medicinal purpose. The Periplus Maris Erythraei mentions weapons of Indian iron and steel being exported from India to Greece.
Early Common Era—Early Modern Era 
The world's first iron pillar was the Iron pillar of Delhi—erected at the times of Chandragupta II Vikramaditya (375–413). The swords manufactured in Indian workshops find written mention in the works of Muhammad al-Idrisi (flourished 1154). Indian Blades made of Damascus steel found their way into Persia. European scholars—during the 14th century—studied Indian casting and metallurgy technology.
Indian metallurgy under the Mughal emperor Akbar (reign: 1556-1605) produced excellent small firearms. Gommans (2002) holds that Mughal handguns were stronger and more accurate than their European counterparts.
Other terms 
- Prastarika: metal trader
- Sulbhadhatusastra: science of metals
- panchaloha, sarva loha: the five base metals (tin, lead, iron, copper, silver)
- The origins of Iron-working in India
- Copper Technology in the Central Himalayas Dates Back to 2000BC
- TKS Metallurgy Bibliography
- Zinc production in Ancient India 
- Wootz steel: an advanced material of the ancient world
- Indian heritage in metallurgy
- Zinc and related alloys
- Smelting of Zinc by Distillation Process
- Iron In Kumaun Goes Back To First Millennium BC D.P. Agrawal and Manikant Shah