The Birth of Metallurgy and its Impact

September 22, 2012 12:29 pm

Introduction

The time is around 9000 B.C.E.  A Stone Age hunter picks his way through a riverbed looking for flint suitable for tools and weapons.  His eye is caught by the sight of a rock that glimmers “far, as from the moon” as the Greek poet Homer would put it over 8000 years later.  It certainly is not flint, but it is interesting, so he takes it home to see what he can do with it.  The rock bends, but does not break or chip under the blows of his hammer stone.  Our hunter can shape it into some little trinket such as a pin that will probably make quite a stir with his friends and family and be a valuable item in trade.  In such a modest way was metallurgy born.
Today it would be hard to imagine our civilization without metals.  After all, just about every manufactured object we have either has metal in it or was made by metal machines and transported on ships, trains, or trucks made of metal.  Without metals, we would literally be living back in the Stone Age.  The development of metallurgy was a long, and sometimes devious process that involved five basic steps.

  1. Identifying and discovering its usefulness .  There is little in nature to suggest the existence of metals or their usefulness.  Our Stone Age hunter managed to find a small copper ingot.  Unfortunately, metals rarely occur in such a pure state.  Instead, we find them mixed with other minerals in rocks called ore.  Ores usually do not present the appearance of anything resembling metal, so the question arises as to how people discovered them.  As with so many discoveries, it was probably by accident.  One likely scenario is that potters would put some minerals containing copper on the pottery to give it a glaze when fired.  The kiln’s heat would separate the copper from the rest of the glaze, leaving little beads of copper lying around.  Further experiments would lead to the realization that other rocks were also ores containing copper.
  2. Locating metals in quantity.   Our potters, wanting larger amounts of the copper ore, find there is little to be found lying on the surface.  As a result, they start digging near the surface deposits and find more copper ore in the ground or the sides of hills.  Eventually, they will find that copper mixes with different minerals to produce a variety of ores rarely resembling each other.
  3. Mining the ores.   Now that they know where the ores are, they have to mine them.  This is one of the more unpleasant aspects of ancient metallurgy.  In fact, work in the mines will become the most brutal and demoralizing job in the ancient world, being reserved for slaves and condemned criminals.  It is unfortunate that the glories of ancient civilizations and the modern civilizations later built upon them would have to depend so much on the intense suffering of slaves whose life expectancy in many of the mines was no more than six months to a year.
  4. Smelting the metal.   Smelting means heating an ore to a high enough temperature that the metal will separate from the rest of the ore, known as slag.  As stated above, the first incidence of smelting was probably by accident in a pottery kiln.  Over the years, metal smiths would come up with various innovations that created hotter fires and the ability to smelt stronger metals such as bronze and iron.  Bellows were invented for blowing air into the fire.  The kiln was enclosed to trap heat.  And charcoal, partially burnt wood that burns at a higher temperature than regular wood, was developed as a fuel.
  5. Shaping the metal into something useful.   There were two basic methods for doing this.  One method was to pour the molten metal into molds.  The other was to pound the metal into the desired shape, such as a sword.

The ages of metals

There were three basic ages of metals in the ancient world, named after the dominant metal used for tools and weapons in that day and age:  the Copper Age (c.4000 – 3000 B.C.E.), the Bronze Age (c.3000 – 1000 B. C.), and the Iron Age (c. 1000 B.C.E. to the present).  They followed this sequence from the easiest metal to smelt and shape (copper) to the hardest to smelt and shape (iron).
The Copper Age saw fairly limited use of copper in the Near East, because copper is a soft metal and not useful for many tools and was also quite expensive for the average person.  Therefore, most people continued using stone tools.
The Bronze Age, during which such civilizations as Mesopotamia, Egypt, and Minoan Crete reach their zenith, saw metals come into their own in the Near East. Bronze is an alloy (mixture) of copper and another metal, usually tin, that is much stronger than either of its components.  The first bronze used was a natural alloy of copper and arsenic.  Unfortunately, arsenic fumes are deadly, and blacksmiths found it quite unpleasant to work with this variety of bronze.  But it did give them the idea of mixing copper with other metals to develop a bronze of copper mixed with a small amount of tin, usually only 1-4% of the total mixture.  However, even that much tin was scarce and had to be sought out in Europe and central Asia.  This was important because trade routes spread ideas as well as goods.  Therefore, we see civilization spreading to Europe and central Asia by way of the tin routes. One drawback of Bronze was its expense, which made it available to a limited number of people.  As a result, Bronze Age civilizations were highly aristocratic societies of narrow classes of nobles and priests ruling over masses of peasants still using stone tools.
Around 1200 B.C.E., a massive upheaval of nomadic peoples swept through the civilized Near East, toppling or severely weakening the older cultures in that area.  The Hittites in Asia Minor (modern Turkey) and Mycenaean Greeks of Trojan War fame disappeared from history at this time.  In fact, the Trojan War was probably part of this upheaval.  As far as our story is concerned, this wave of invasions seems to have disrupted the trade routes that supplied the Near East with its bronze.  This put a rather abrupt end to the Bronze Age.
By this time, people were quite hooked on the idea of metals, and started looking for a substitute for bronze.  That substitute was iron.  However, iron presented a severe drawback.  It has a smelting temperature much higher than ancient furnaces could obtain.  All these furnaces could produce was a spongy mass called bloomery iron.  This had a tensile strength little better than copper.  Fortunately, smiths kept working with bloomery iron and learned how to use it.  Hammering out the impurities led to an improved bloomery iron that was much better than copper, but a poor substitute for bronze.  Heating it next to charcoal made the carbon in the charcoal combine with the iron.  This created a crude form of carburized steel with a tensile strength twice that of bronze.  Even without being able to smelt iron, ancient metal smiths had found a way to make it useful.
Iron has been called the democratic metal because it is so plentiful and so many more people could afford it compared to those who could afford bronze.  It could well be that iron is the metal that pulled most people out of the Stone Age.  It was not until the masses could arm themselves with iron that democracy could evolve in such places as the Greek city-states.  Although we today use many other materials such as plastics, steel made from iron is still the metal that we make our machines from.  Even today, we live very much in the Iron Age.
Metals have been very important to civilization throughout history by creating tools that could do old jobs better than ever and new jobs never done before.  For example, iron tipped plows in medieval Europe would lead to more land under cultivation, more population, and the rise of towns and civilization in Europe.  Metals allowed for more extensive clearing and exploitation of forests since an iron axe can fell trees much faster than a stone axe can.  The better housing and food supplies made possible by metals led to a higher standard of living for people who could be better fed and housed because of metal tools.
Metals also created new sources of wealth in their own right.  The value that people placed on gold, silver, and even bronze led to a common medium of exchange that everyone agreed was valuable.  This made trade much easier.  For example, a leather tanner wanting grain might not be able to find any farmers that wanted to trade their grain for leather.  But if the tanner could sell his leather to a third party for silver, any farmer would be willing to trade grain for the tanner’s silver because everyone recognized silver as something worth having.  As a result, all three parties got what they wanted without having to take the trouble of finding someone with exactly what they needed and willing to trade exactly what they wanted.  Precious metals made trade easier, expanded trade, and usually benefited all parties involved.  As a result, just about everyone’s standard of living went up.
One final stage was the invention of coinage around 700 B.C.E.  The advantage of coinage was that a government guaranteed the weight and purity of its metals.  As a result, people did not have to worry about being cheated with fixed scales or ingots of gold or silver debased with other less valuable metals.  The higher level of trust coinage generated further expanded trade.
Metals did create problems also.  The new wealth that metals created also led to more wars and conflicts over that wealth.  The need for charcoal as fuel led to deforestation, erosion, and possibly climactic changes in such areas as Asia Minor and the Indus River valley.  One theory suggests that the Indus River civilization declined because deforestation caused a hotter, drier climate and crop failures.  For the first time, human use and misuse of power was backfiring against us.  Metals have indeed proven to be a mixed blessing, but one we would not want to live without.
With the end of this unit around the year 1000 B.C.E., we see the human race has attained most of the skills that will help it survive for several thousand years.  Not until the Industrial Revolution in the late 1700’s will we see many new technological innovations changing people’s lives.  Until that time, most innovations will be refinements of the skills first developed in the centuries when civilization first emerged.

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