Metallurgy

India was the world-leader in Metallurgy for more than 5,000 years. Gold jewelery is available from 3,000 BCE. Brass and bronze pieces are dated back to 1,300 BCE. Extraction of zinc from ore by distillation was used in India as early as 400 BCE while European William Campion patented the process some 2,000 years later. Copper statues can be dated back to 500 CE. There is an iron pillar in Delhi dating back to 400 CE that shows no sign of rust or decay.

The earliest know book on metallurgy was known to be written by Nagarjuna in 10th century. The book Rasaratnanakara addresses various metallurgical topics such as:
Preparation of liquids (rasas) such as MercuryExtraction of metals like Gold, Silver, Tin, and Copper from their ores and their purificationThe processes of liquefaction, distillation, sublimation, and roastingIndia was invaded by Mohammedans during the time of Nagarjuna. It is possible that Nagarjuna's texts fell into the hands of the invaders, who could have transmitted these Indian Metallurgical sciences to the outside world.

Metallurgy in India has a long and varied history. Bronze and copper were known during the period of the Indus Valley Civilization. The recovery of metal articles (including a bronze dancing girl) and the discovery of crucible with slag attached are clear indicators of the knowledge of casting (pouring molten-hot metal into moulds of the desired shape and size) and forging (hammering hot metal into required shapes). Further, this points to the fact that these early peoples could produce and handle temperatures as high as 1084° C (melting point of copper), as also 1065° C (gold), 960° C (silver), 327° C (lead), and 232° C (tin). Working with iron with its melting point at 1533° C was inarguably a later achievement.

Mohenjodaro, Harappa and Lothal are the three major sites of this civilization. At Lothal in the state of Gujarat, two types of kilns have been excavated, One, a circular kiln that measures 1 metre in diameter, that was most probably used for smelting copper ingots; the second, a rectangular kiln measuring 75 by 60 cms. with a depth of 30 cms. This is believed to have been used for casting tools.

The many metal discoveries at Lothal include figure, amulets, pins in the shape of a bird-head, miniature figures, and tools such as a curved or circular saw, a needle with an eye at the piercing end, and a bronze drill with twisted grooves. This last is by far the most important find of ancient tools because this single item led to an unparalleled precision at the time, and is widely regarded as the precursor to modern machine tools.

The above-mentioned tools are exceptional in the entire Indus Valley civilization, and neither do they bear resemblance to Harappan tools. Indeed, Lothal was already a prosperous town prior to the arrival of the Harappans sometime around 2450 BC and till 1600 BC.

One thousand and fifty BC is usually accepted as the year the Iron Age began in most of India. Iron is mentioned by the Atharvaveda, referred to specifically as ayas. Previous to this, the Vedas used the term ayas as a generic one for metals : the Brahmanas and the Upanishads referred to Lohitayas (i.e. red metal or copper) and Krishnayas (i.e. black metal). One thousand BC is the accepted date for the appearance of extracted iron.

Iron and its technology gave momentum to the process of urbanization, and the lives of the peoples changed in reflection. 

Iron was closely associated with : 

o Painted Grey Ware Culture -- the iron objects of this association date back to 1025 +/- 110 BC. Excavations have revealed arrowheads (including leaf-shaped ones), daggers, hoes, adzes, spearheads with tongs, fish hooks, and plain tongs. A vital site - Atranjhikera - has yielded implements at practically every level of excavation! Other sites are Hastinapur, Alamgirpur, Kausambi and Ujjain. 

o Black-and-Red-Ware-Culture -- objects discovered at Eran in the state of Madhya Pradesh date back to 1250 BC and 700 BC, according to C14 dating. Another site, Nagda, has 59 objects, all belonging to the period 750-500 BC. These include a double-edged dagger, the round socket of a broken axe, arrowheads with a biconical cross-section, a celt with a wide cutting edge, spoon, nails, clamps, and knife blades. 

o Megalithic Culture -- While the rest of the country proceeded from the Neolithic to the Copper and then to the Iron Age, South india moved directly from the Neolithic to the Iron Age. At Hallur, the Iron Age is believed to have begun in 1105 BC, while the rest of the South coincided with the North i.e. approximately between 1050 and 950 BC. Spread throughout this region, implements and tools are marked by their similarity. Flat iron axes, sickles, spades, daggers, swords, knives, chisels, tripods, horse-bits, frying pans, ladles and even bangles - all point to a usage for both domestic and warfare purposes. Taxila stands apart due to the clear Graeco-Roman influence, for example, ladles with vertical handles, folding chairs, candelbras, plate armour for men and horses, cheekbars. Of special interest are the arrowheads that are distinctly Mediterranean in style, and made their appearance in both distant regions in AD 1!

The Special Four

1) The Iron Pillar in the Qutb Minar complex at New Delhi is an AD 310 structure, and has survived corrosion-free! It stands at 23 feet & 8 inches, upper diameter - 12.5 inches, lower diameter - 16.5 inches, and weighs 6 tonnes. Analysis of the pillar - iron: 99.720%, carbon: 0.080%, silicon: 0.046%, sulphur: 0.006%, phosphorus: 0.114%, manganese: negligible. The low levels of sulphur and manganese, and the relatively high level of phosphorus, are credited with its rust-free existence.

2) Iron Pillar at Dhar (near Indore) is believed to have been built during Chandragupta Vikramaditya's reign, between AD 375 - 413. Originally 50 feet in height, it has an average cross-setion of104 square inches, and weighs 7 tonnes. Unfortunately, the pillar is now in three parts.

3) Iron beams (29 of them) at the temple at Konark (near Puri) - the largest measures 35 feet by 6 inches, and the second in size, 25 feet by 6 inches. Both have a cross-section of 11 inches by 11 inches. The temple was constructed sometime around AD1240.

4) The 232 beams of the twelfth century Gundicha Bedi Temple at Puri! The longest beam is 17 feet in length, and cross-sections of the beams vary from 6 inches by 4 inches to 5 inches by 5 inches.

In Arthasastra : The Wisdom of the Wise:

Kautilya's magnum opus, the Arthashastra, is regarded by many a scholar as the last word in sense and cunning. Here, we briefly focus on the former aspect! Written in the fourth century BC, the work discusses metals and minerals, the purification of their ores, the extraction and working of metals, as well as their alloys. On one hand, the book suggests the purification of ores by chemical treatment with iron or alkalis (i.e. plant ashes). On the other, it recommends the use of charcoal and chaff (waste products of food preparation) in limekiln and for smelting iron. Clearly, recycling mattered! In addition, there are pointers to the location of mineral deposits. 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.

The Rig Veda refers to ayas, and also states that the Dasyus had Ayas (RV 2.20.8). In RV 4.2.17, "the gods [are] smelting like copper/metal ore the human generations". The references to Ayas in the Rig Veda probably refer to bronze or copper rather than to iron.

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 6.1.3.5 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) and the Uttarabhaga of Silparatna) describe the lost wax technique in detail.

The Silappadikaram says that copper-smiths were in Puhar and in Madura. According to the History of the Han Dynasty by Ban Gu,Kashmir and "Tien-chu" were rich in metals.

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. He wrote the treatises Rasaratnakara, Rashrudaya and Rasendramangalthat 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. He also wrote Uttaratantra as a supplement to Susrutasamhita, dealing with preparation of medicinal drugs, and an Ayurvedic treatise, Arogyamanjari. His other treatises are Kakshaputatantra, Yogasara and Yogasatak. Because of his profound scholarliness and versatile knowledge, he was also appointed as Chancellor of the famous University of Nalanda.

Varahamihira in the sixth century AD indicates the hardening of steel in his Khargalakshanam:: '' The red hot steel should be plunged into a solution of plantain ashes in whey, which is kept standing for twelve hours and then it should be sharpened on the lathe.''

Vrinda discussed the process of killing iron (i.e. obtaining iron oxides). He insists that iron first be ignited in fire and then immersed in the juices of Emblic myrobalan and Trewia nundiflora. Next, it should be exposed to sunlight, and then again macerated in certain other plant juices. Last, it should be placed in a mortar and rubbed.

The twelfth century Brahmanical Tantric text Rasarnava holds forth on the colour of flames, the processes of killing metals, and the test of a pure metal. The last - ''A pure metal is one which when melted in a crucible does not give off sparks nor bubbles, nor spurts, nor emits any sound, nor shows any lines on the surface but is tranquil like a gem.''

Another text Rasaratnasamuchchaya speaks of iron as one of the pure metals, and the three categories thereof: 

(i) Mundam (wrought iron) is of three types - one is the mridu, that is glossy, will melt easily but is difficult to break; the second, kunthum, that does not melt easily; and the kadaram that will easily break under the hammer;

(ii) Tikshnam (cast iron steel) - of six types, ranging from the line-free and rough and breakable type to the sharp-edged type that is difficult to break.

(iii) Kantam is of five types - bhramaka (that can make iron move about), chumnbaka (that which 'kisses' iron), karshaka (that which attracts iron), dravaka (which melts iron easily), romakanta (which expels hair-like filaments upon breaking).

Other metals:

Zinc mining and smelting were known in the fourteenth century, and soldering was a common practice. By the eighteenth century, steel manufacture was a regular industry, particularly in Mysore. Seringapatnam was famous for its steel wires for musical instruments, while iron utensils and furniture were hallmarks of the smiths of Birbhum in the state of Bengal and Munger in the state of Bihar.