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From 2000 to 1600 BC highly advanced bronze technology spread throughout the Near East and Europe. Both Minoan Crete and Mycenaean Greece extensively used bronze, particularly for weapons. Beautifully worked bronze pieces dating from around 1600 BC were found in the royal graves uncovered at Mycenae. Wessex and Brittany developed wealthy societies founded on easy access to tin and copper; Scandinavia, with no metal resources, imported bronze in return for furs, skins and amber. Valuable bronze pieces, such as the Trundholm sun chariot, were cast into bogs as offerings to the gods. Luristan, in Iran, developed an intricate and artistic bronze culture and farther east, towards India, open-mold copper casting persisted.
At about the same time that the Bronze Age penetrated northern Europe (1800-1500 BC) an important culture arose in China. From a purely Neolithic tradition, China under the Shang dynasty leapt into the Bronze Age, producing magnificent examples of bronzework, including cast vessels of amazing style and beauty. During this period new techniques were added to the original methods of close-mold casting and the 'lost wax' technique that had been invented in the second millennium BC, making possible the production of large scale items. A byproduct of bronze technology was the stimulus that it gave to other crafts, especially carpentry. The invention of the spoked-wheel chariot, innovations in boat building and furniture making all owe much to the availability of good bronze tools, made possible by the advances in metalworking.
Before the Iron Age
Bronze today denotes a whole series of copper-tin alloys, each of which is made for some special tool, implement or purpose. The word is even used, quite wrongly, for alloys of copper and other metals than tin.
Historically, bronze is a most important metal. The Bronze Age of the archaeologists was the first phase of true metallurgy. Man had known metals well before he practised metallurgy. Certain metals, such as gold, silver, iron and copper, occur as such in nature. These native metals are often found in brooks or on the banks of rivers in the form of nuggets and pebbles, but sometimes very large pieces turn up. Boulders of native copper weighing several tons are known to occur along the banks of the North American lakes, and the Indians had chipped off pieces long before the advent of the white man.
However, prehistoric man (and this holds true for many primitive tribes even to the present day) did not practise metallurgy - that is, he did not know how to melt, cast and work such metals. He regarded these nuggets as coloured stones to be cut, ground and polished like precious stones, and he fashioned them into small amulets and beads which he treasured.
Then prehistoric man discovered an important fact - that the native metal liquefied with heat. He found that a stream of molten metal poured into a depression in sand or a cavity made in a stone would take its shape and retain it after cooling and solidifying. Having hit upon the true nature of metals, he could now melt them and cast them. About the same time he discovered another most important fact. If some of the precious stones which he had treasured for centuries, such as malachite and lapis lazuli, were heated with charcoal, they would yield a metal identical with the most common native metal. To put it in modern scientific terms, he discovered that some of these stones were copper compounds or copper ores, which when reduced with charcoal (i.e. carbon) would yield copper. These two discoveries made him a true metallurgist who began to make use of the basic properties of metals to shape instruments and tools, which were often better than the tools he had always shaped from wood, bone or horn. Man became master of a new technique which allowed him to create new shapes and forms of tools.
These discoveries took place somewhere about 3500 B.C. and probably in Eastern Persia and Afghanistan. Soon the art was brought to the Armenian and Caucasian mountain ranges, whence it spread to Egypt, Asia Minor and Europe. The production of copper from its coloured ores made the early smiths try the same process on other coloured stones, and thus they soon learnt to smelt the ores of lead, silver and antimony.
The art of alloying - that is mixing these metals in different proportions - arose from the two facts that it is difficult to cast copper in intricate moulds, and that pure copper is not very hard. How the new easily castable and much harder copper-tin alloy was first discovered we do not know. Probably it was obtained when tin ore or 'stream tin' was used to refine copper in a final smelting operation. Anyway, bronze became known shortly after the introduction of copper. Since the early smiths selected their ores by colour and form only, without any knowledge of chemical analysis, they made bronzes containing eight to twelve per cent of tin when aiming at an average of ten per cent. This bronze was eminently suitable for tools and weapons. Later on, special bronzes containing more tin were developed for the manufacture of mirrors of polished metal (twenty per cent), and for bells (thirty per cent).
However, tin ores were not readily available everywhere, and they were certainly much rarer than copper ores. In Egypt, where tin ores were completely absent and had therefore to be imported, bronze became common only by 2000 B.C. The inhabitants of ancient Mesopotamia were more fortunate in obtaining tin from the mountains to the north. Even so, the analysis of early Mesopotamian bronzes shows that before long these deposits could no longer satisfy the large demands; the percentages of tin had therefore to be reduced. For certain purposes 'bronzes' could be compounded by alloying copper with lead or antimony. For art objects, or for statues of the gods, such inferior bronzes were good enough and were substituted throughout the Near East.
For the manufacture of tools and weapons new sources of tin ores had to be found; and the early metallurgists started to look for them in foreign countries. The deposits of the Balkans, of Bohemia, of Brittany and northern Spain and finally those of Cornwall were discovered. As these remote regions were explored, the art of metallurgy was taught to the inhabitants of Central Europe, who soon became equally skilled, and transmitted the lore of the smith to the tribes of the West. By 2000 B.C. tin ores were also being smelted separately, so that instead of a trade in ore, bars of tin were produced and traded from hand to hand. This again allowed the smiths to compound their alloys more closely and to produce alloys of different tin content - a range of bronzes, in fact, for different specialized purposes.
As the craft of the smith became more complicated, specialists of different types arose, the miner extracting the precious ores, and the metallurgist making bars and cakes of crude metal, which were then traded to the great cities and centres of civilization. Each metal had its own form of ingot. Gold and silver were usually cast in rings or small bars; tin came in I-shape ingots, one on each side of a pack-animal. Copper and bronze were cast in round flat cakes in prehistoric western Europe, and in the form of double-axes in some parts of central Europe. In the eastern Mediterranean they took the shape of an ox-hide weighing some thirty kilograms (one talent); and it is well to remember that the Latin for 'money' (pecunid) is derived from 'cattle' (pecus). These bars of crude metal were, indeed, not only the raw material for smiths, but they also served as a primitive kind of money. Hence the currency units of the ancient civilizations were often weights of metals and other commodities as well. The primitive method of casting copper in round cakes prevailed in Japan till the nineteenth century. Water was sprinkled with a straw brush on the molten copper in the furnace. A crust was formed and hooked out, and then plunged into cold water.
In the big cities these bars were then processed by different specialists. Often the state or the city authorities bought ingots and kept them in a storehouse to be handed out to smiths for the manufacture of certain tools and weapons, for which they were paid per unit. Big centres of copper and bronze production like Cyprus could manage the market. We have cuneiform tablets telling us how the king of Cyprus delayed the delivery of large consignments of copper to Egypt, although he had already been paid. In fact, countries and states which possessed rich ores and a metallurgical industry now became a political force. One of the Books of Maccabees rightly reminds us of the conquest of Spain by the Romans because of its iron, tin, silver and copper ores; and Hannibal could never have invaded Italy without the mining industry of Cartagena in Spain. The Phoenicians and Carthaginians grew rich on the trade of metals, even when living in a country poor in ores. Earlier the Cretans, as Egyptian wall paintings show, had traded bronze ingots southward to Egypt.
By 2000 B.C. bronze had displaced the old stone and wooden tools in general, but not completely and not everywhere. For many things, such as ploughshares or arrow-heads, stone remained a more appropriate material. Bronze was always rather an expensive alloy because of its tin content. The ancient smiths used to collect old and broken bronze tools and weapons and melt them down and recast them. By 1000 B.C. bronze was threatened by a new metal, iron, and partly displaced by this cheaper competitor. But the art of the Bronze Age smith in casting and alloying was never lost. Bronze had many virtues. When artillery and firearms were invented it still was the only metal at first from which cannons could be cast. Even to our day it is supreme for many purposes, such as engine bearings. Its value increased with the discovery of new metals which could be added to the copper-tin mix. Bronzes thus came to play a large part in modern coinage and in electrical machinery.