China has a long and brilliant history of metallurgy and
casting. Its splendid casting techniques ushered in the resplendent
Bronze Age. Perfect workmanship brought about exquisite pieces of
art.
An accurate mixture of metals for alloy, a division of work
between the extracting furnace and the smelting furnace, the
replacement of the pottery base furnace by the clay furnace, the
appearance of the sand furnace and the furnace of comprehensive
materials, the evolution of the air blower from the air bag to the
bellows, the use of the metal mould method and the lost-wax method,
the ingenious application of the way of combined moulds and
separate casting and the way of separate moulds and combined
casting and the development from the casting of a single surface
shaping furnace to the casting of pit shaping furnaces embodied the
great wisdom of the Chinese nation and the scientific and
technological progress in ancient times. Summing up their
experiences gained over a long period of time, our ancestors
acquired a good grasp of metal smelting and casting techniques. The
book Xun Zi summarizes the essentials of bronze casting
technology as follows: "Correct moulds, fine mixture of copper and
tin, ingenious workmanship and consummate smelting."
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The three-dimensional models, simulated operating demonstration
and operation by visitors at the exhibition room demonstrate the
process of casting bells in ancient times.
The day mould method and the lost-wax method were the main
methods used to cast bells in ancient China.
I. The clay mould method included the procedures of making outer
moulds, making inner moulds, drying the moulds, combining the
moulds, smelting and casting.
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Outer moulds could be made on models or with a scraper. Inner
moulds could he made with a scraper or a molding set. The drying
process was designed to make the moisture content in the mould
evaporate thoroughly so as to increase the strength of the
mould.
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Crucibles and air bags were the main smelting equipment in the
early days. Large smelting furnaces and bellows were used during
the Ming and Qing dynasties.
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II. The lost-wax method included the procedures of making inner
moulds, applying wax and carving, making outer moulds, melting wax
and drying the moulds, smelting and casting.
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1. Build an inner bell mould with clay; 2. Coat the inner mould
with butter mixed with wax; 3. Carve the solidified wax into the
desired shape of the bell; 4. Coat the wax with clay and leave an
outlet for the wax; 5. Heat and melt the wax to make the wax flow
out of the outlet, form a cavity, and continue the heating to dry
the bell mould thoroughly; and 6. Melt metal and do casting.
An ancient bell was cast through those procedures.
