A Living Portrait of India
The Past has a Tale to Tell!
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 :
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.
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.
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.
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:
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.