An
Historical Perspective
The
earliest bronze was probably made by accident.
Some copper ore deposits also naturally contain
small amounts of tin. When such ore is refined,
the metal looks like copper but is harder and more
useful for making tools, weapons, and artwork.
Sometime around 3,000 BC, metal-workers in
Mesopotamia found that if they added a small
amount of tin ore to the copper ore during
smelting the resulting metal was harder and thus
more useful than either tin or copper alone. They
had created the alloy bronze. Furthermore, the
addition of the tinstone reduced the temperature
required to melt the metal and, once melted, the
bronze was more fluid and easier to cast. The
first examples of bronze used in any quantity have
been found in the tombs of Sumerian kings who
ruled in the lower Mesopotamian Valley. With
increased trade in the eastern Mediterranean, this
bronze technology made its way into Egypt, and the
Egyptians were using it in a limited way by around
1,500 BC. However, bronze was not in common use in
Egypt until about 1,000 BC
Bronze
was also stronger than iron, another common metal
of the era, and quality steels were not available
until thousands of years later. Nevertheless the
Bronze Age gave way to the Iron Age as the
shipping of tin around the Mediterranean Ocean
ended during the major population migrations
around 1200 - 1100 BC, which dramatically limited
supplies and raised prices.
The
Greeks developed bronze casting enormously. For
sculpture, bronze offered freedom from the
limitations of marble which they explored to the
full. A famous example was an enormous bronze
statue of Apollo. Cast in sections, when assembled
it towered 105 feet above the harbour entrance to
Rhodes, with one foot on each pier head. The
statue weighed some 360 tons and was one of the
seven ancient wonders of the world. The Greek
foundrymen had also established some useful
alloys, recognisable today. As Pliny mentions in
his Natural History "The composition of
bronze for statues, as well as for sheets of
metal, is as follows: the ore is melted and to the
melt is added a third part of copper scrap-that
is, used, second-hand copper. This scrap contains
an intrinsic, seasoned brightness, since it has
been subdued by friction and tamed by use. Tin is
also alloyed with it, in the proportion of one
part of tin to eight of copper.
"Then
there is the bronze referred to as 'suitable for
moulds'; this is very delicate because a tenth
part of lead and a twentieth part of silver-lead
is added; it is the best way to impart the colour
called Grecian...." (Natural History
34.97-98).
Until
cheap steel became available in the mid 19th
century, the limitations of the maximum
temperature of wood or coal fired furnaces meant
that bronze continued to be cast and iron was
wrought. The painstaking beating and folding of
iron sheets created an early version of steel,
used mostly for critical applications such as
sword blades and tools. The legend of the sword in
the stone is reputedly based on the process of
forging a steel blade. The person who possessed
the technology to create a better sword was in
those days more likely to be king.
Index
:: Projects
:: Bronze Types :: History
:: Sand Casting :: Patternwork
:: Fabrication :: Lost
Wax :: Other Things
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