The casting of the bronze
drums of Dong Son is a complex process requiring high order of
techniques and artistic skills.
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It was first necessary to produce a hollow clay core to minimise
weight and ease its manipulation.
Separate clay pattern moulds would then be prepared, circular
for the tympanum and rectangular for sections of the mantle.
The surface of the clay received ornamentation in more than one
way. It could be impressed with a patterned old to create the
panels of geometric ornament, or for more individual motifs or
decorative elements, it could be incised with a stylus.
This pattern old would then have been filled with molten wax,
such that the wax filled and duplicated the chosen decor.
It would then have been necessary to transfer the sheets of cooled
wax to the clay core, having first place the bronze spacers strategically
into the wax until they reach the surface of the pattern old.
This procedure resulted, in effect, a wax drum over a clay core.
Investment of the wax in a layer of very fine clay followed before
the assemblage was covered in a coarse clay coat. It was then
necessary to melt out the wax, and preheat the clay old. The critical
point was then reached for the pour, in the case of larger examples,
of nearly 100 kg of molten bronze into the conduits to reproduce
in metal the wax image of the drum.
Asia, Charles Higham, 1996