Today, we see metal fired in the arts. The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
The stone age drew to a
close around 3500 BC as we took up metals. We began
the new age by picking up the odd gold nugget, the
stray lump of meteoric iron, and the glittering
piece of alluvial silver. We began by hammering
ornaments from those natural metals.
Natural deposits of metal are sparse. Yet the
malleability of metal opened huge possibilities for
artisans. It didn't take long to find we could
expand the supply of metals by smelting ores. We
smelted the first copper by accident when potters
made glassy glazes from copper-based pigments.
For smelting, we needed both ore and forests of
wood for fuel. Both were plentiful in the northern
part of present-day Iran and in Russia above it. So
we began serious copper smelting outside the
ancient cradles of civilization.
But smelting meant hotter fires than any we'd ever
made. Fire had also been brought under control by
the late stone age pottery industries. Now we had
to add forced draft to the old pottery kilns. We
had to stoke fires hot enough to liquefy gold and
copper -- hot enough to refine them into pure
components.
You see, surface gold is usually an alloy. It has
silver mixed in it. Egyptian artisans first used
each natural alloy of gold and silver as a
different material. They used the different colors
of gold alloys to create exquisite objects of art.
Most copper ores are also impure. They're usually
mixed with natural tin. We made the hard,
copper-tin alloy that we call bronze accidentally,
before we learned how to control composition. Only
in Egypt, where copper ore was fairly pure, did a
copper age give way to a bronze age. That happened
when Egyptian craftsmen started alloying their
copper to make it stronger.
It was 1500 BC before we could finally refine the
natural alloys into elements. We finally mined tin
separately and purposely alloyed it with copper to
make the best bronze.
Iron melts at 3000° F. It was 1200 BC before we
figured out how to reach temperatures like that.
When we did, iron became the metal of choice in the
Western Mediterranean world.
1200 BC was also when the Old Testament books began
to take shape, and you can read our new fascination
with metal in them. Those books are shot through
with gold, silver, iron, copper, lead and bronze.
The new metals touched our imaginations. By 1000 BC
metal ingots, called talents, were the new medium
of exchange in the Mediterranean basin. Up to now
each stage in the use of metal had been driven by
the arts. Now metal was poised to return the favor
and to reshape civilization itself.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
