Sunday, November 2, 2014

IRON SMITHY - craft -1

IRON SMITHY - craft -1
Post 107   by Gautam Shah ➔

Since prehistoric times, nearly every region of the world and every culture had some knowledge about iron. It was perhaps not sufficient enough to explore the very abundant resource material. Bronze was easier to extract and work, but Iron was tougher than bronze. It was less toxic for food and water storage, except for rusting. Pure iron as meteorite nodule is soft but unavailable in sufficient quantity. First lesson of iron-smithy was the realization that smelted Iron (with its impurities, chiefly of Carbon -automatically included during smelting) is a very hard and durable material. First Iron utilities were of Cast Iron varieties.

Iron Bloom

Lack of copper, and the abundance of iron everywhere encouraged developments in iron working. Large furnaces produced vast quantity of iron that was not processed further, but was shaped into various forms (vessels and solids) through casting and moulding. The next Iron smithy craft was forming sharp edged tools for home, agriculture, hunting and warfare. This was done by forging a shape and annealing-hardening treatments. The treatments and reheating showed how to adjust carbon content as well as other impurities. It is believed that by 5th C. BC, bronze was replaced by iron as the material for utensils forming and weapons making.

Iron making must have started in India, earlier then 1800 BC, as Rig-Veda mentions Ayas (metal) or Shyam or Krsna Ayas (black metal). A description like ‘for as a ploughshare that has got hot during the day when thrown into the water splashes, hisses and smokes in volumes’ shows use of quenching processes.

First crucible-based steels were developed in India, around 300 BC. In this process iron was mixed with glass, as the mixture cooled glass would bond with impurities, and float to the surface as scum. The porous walls of the crucibles added the carbon. This steel was exported throughout the Middle East, where it was known as Faulad (Persian). Faulad or wootz steel (in Europe) has a Kannada term(Language of Indian region of Karnataka) for it, ukku.

 Water pattern on Damascus steel swords These images are of 1800 AD production

Faulad was processed further to produce Damascus steel. Swords and other sharp cutting edge tools made from Damascus steel had distinctive patterns of banding and mottling reminiscent of flowing water. In India though for a long time after 600 BC, cast-iron was used for making spikes, knives, daggers, arrowheads, bowls, spoons, saucepans, axes, chisels, tongs, door fittings etc. India had mastered the craft of casting very large sized pillars.

Iron Pillar Delhi India

Chinese were able to melt the Iron and cast it into desired forms. This method was less labourious than individually forging each piece of iron from a bloom. But most remarkable point was that China’s iron smelters achieved a temperature of 1130 °C, hot enough to be considered a blast furnace. The devised very efficient bellows of leather to deliver a continuous stream of air into a furnace. Chinese smiths had also mastered the technique of melting wrought iron and cast iron together to produce a material of intermediate carbon content that is steel. The process was called ‘harmonizing the hard and the soft’. This was to be the basis of casting of Iron statuettes.

Chinese poodle and Blast furnaces

The furnaces and bellows as used in Roman time Europe worked at 1100° -1200° C, so Pure Iron’s melting point temperature of 1540°C was difficult. Iron at this temperature did become soft but not liquid. It was a solid state conversion requiring chemical reduction of the ore. Ore was placed in a pit and mixed with hot charcoal fire. After a sustained temperature of 1100°-1200°C, the slag fell to the bottom leaving the spongy mass of iron called Bloom. The bloom while hot, was pounded, into a denser mass called wrought iron.

In later periods, both the processes, the cementation and the crucible process, were practised. ‘In a cementation process wrought iron was heated with charcoal (to add carbon) without exposure to air, whereas In a crucible process wrought iron bars were melted in crucibles with charcoal.’ For wootz steel was made by a different type of blast furnace. Here a charge of Iron ore and a charcoal material was added in the crucible. It was held at high temperature for long time, for the bloom to absorb enough carbon and reduce the melting point of the iron. Cast buttons or disks were reheated in the direct flame to a temperature just below their melting point. The buttons were then forged together by pounding.

Roman steels provided Hooks, harness rings, tires, chisels, adzes, saws and shovels, but not the damask swords. Roman artefacts include few items of case-hardened sharp edges, but architectural craft uses were rare.

Roman-Greek attitude to Metal making is exemplified by Aristotle. He noticed there were large amount of unattractive metals in the ground such as lead, iron, and Tin. He thought every thing grows (develops) to perfection, and so these metals in stages can grow into Gold. Ancient miners blocked the mines to let Earth grow the metals in her womb. The ancient Greeks believed that Iron rusted because elements like water, fire, air left Iron leaving the Earth-rust behind.

Greek metal smiths worshipped Hephaestus. Greeks placed small dwarf-like statues of Hephaestus near their hearths. He used the fire of the forge as a creative force, and had twenty bellows that worked at his bidding. He designed Hermes' winged helmet and sandals, the Aegis breastplate, Aphrodite's famed girdle, Agamemnon's staff of office, Achilles' armour, Heracles' bronze clappers, Helios' chariot, the shoulder of Pelops, and Eros' bow and arrows. He was a crippled god of fire, metalworking, and craft, with the tools of a smithy hammer, tongs and anvil. His crippled, lamed and ugly appearance is believed due to effect of arsenic poisoning, a common problem with all metal smiths. His sacred animals were donkey, dog and crane. He was husband of adulterous Aphrodite (Greek goddess of love, beauty, pleasure, and procreation and Roman equivalent of Venus).

Hephaestus was Roman equivalent of Vulcanus. Vulcanus (Vulcan) was feared for his destructive potential and associated with the volcanic power of the earth, but Hephaestus was gentle. Another mythical figure of Scandinavia was metal working Thor. His hammer was unbreakable, struck its target without fail, and no matter how hard and how far he threw it, always came back to him.

Forge of the Vulcan


hephaestus-aphrodite-forge


 Roman God of Fire Forge and Anvil
.

No comments:

FIRES in SCHOOLS of ARCHITECTURE

Post 150 -by Gautam Shah  . A recent fire in Glasgow School of Art, designed by Charles Rennie Mackintosh has become hea...