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How were bronze vessels made during the Shang and Chou dynasties?
Many years of archaeological efforts and a series of investigative
trials and experiments in casting have uncovered some of
the steps by which they were produced. The process can be
generally divided into two primary phases: "smelting"
and "casting".
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Smelting
is the process of extracting a metal from its ore and then
refining it to a higher purity. In the case of bronze, it
is an alloy (mixture) of the metals copper, tin, and lead.
Once this process is complete, the raw materials (metals)
are transported to political centers and large settled communities
with the requisite technology to undertake the process of
casting. |
Copper ingots excavated from an ancient smelting site at
T'ung-lü Mountain, Ta-yeh, Hupeh
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Stills from the animation for casting techniques
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This part of the exhibit offers a reconstruction of what
raw materials may have looked like in the smelting process
of the pre-Ch'in era, based on archaeological evidence derived
from an ancient mine and smelting operations at T'ung-lü
("Bronze Green") Mountain, located in the district
of Ta-yeh ("Great Refining"), Hupeh. At the same
time, it presents a virtual representation of a possible
casting process derived from the efforts of many researchers
on early technology. Furthermore, the artifacts themselves
reveal hints of the casting procedures used, but these are
usually well hidden. Fortunately, with the advent of modern
x-ray photography, vestiges of the original casting process
can now be thoroughly revealed.
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X-rays of various bronze objects
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Information
on Mining Areas |
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Natural Treasures Buried Below "Copper Grass"
Elsholtzia
is a kind of special plant that grows well in soil with
a high copper content. Since copper is an important element
for its growth, the places where this grass-like plant thrives
are almost always located not far from a rich natural source
of copper ore. Hence, it was given the name "copper
grass". |
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Ores
Used for Smelting
Two
types of ore were used for smelting copper: copper oxide
and copper sulfide. Copper oxide was used relatively early
in the history of copper smelting, because it is found
in veins nearer to the surface, is marked by brighter
colors that make it more distinguishable, and is easier
to process.
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Never-ending
Treasures of Ancient Mine Shafts
Modern
geological surveys show that the majority of copper deposits
in China are concentrated in four main areas. Located in
the middle and lower reaches of the Yangtze River, Mt. Chung-t'iao,
the Szechwan-Yunnan area, and Kansu Province, these account
for two-thirds of the total amount of copper produced. During
the surveys of these areas, geologists also have discovered
evidence of ancient mine shafts in almost all the quarries. |
Distribution map of ancient mining areas
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Advanced
Facilities in Ancient Mines
Though
the mines are ancient, the safety of their facilities do
not pale in comparison to those of today. Despite the vast
expanses of time between then and now, ancient mining technology
is still being used today! |
Mine and ore separation troughgh
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Born
of Flames: The Smelting Process
Refining
the ore to extract the raw metals for use in casting (in
this case, bronze) is the prime objective of a mining area.
The melting point of pure copper is 1083°C. In order to
acquire raw materials of the highest purity, a mining area
must have many high-temperature smelting furnaces. |
Diagram of a reconstructed furnace
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The
Workshop for Casting Bronze
The Advanced Art of Bronze Casting
The bronze
casting techniques developed in ancient China reached heights
that rival or even surpass those of modern methods. First
came the piece-mold process, followed by the lost-wax method.
The creation of the mold was one of the most important stages
in the casting process, because the craftsman could determine
the size and shape of the final piece. In other words, it
became the "model" for the end product. The evolution of
the piece-mold method began with the casting of the whole
piece followed later by separate casting and the combination
of individual pieces. The lost-wax method allowed for the
creation of exquisite openwork in the details of bronze
pieces. |
Simulation of the bronze casting process
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