|The casting of coins during the Han|
In the article A Han Dynasty Coin Mold, H.F. Bowker describes a Wu Zhu coin mould that belongs to Coole's collection. He describes it as we see in fig. 1 as baked tile moulds stacked on top of each other, encased in a porous clay sheath. The sheath is applied to keep the tiles in place. Vegetable matter, which is mixed into the clay, burns and leaves pores in the clay that are necessary to let gasses escape during the casting. Bowker suggests the possibility that the mould assemblies were not baked, but only sun-dried. However, Barnard (p. 34) has an illustration showing a coin mould baking kiln from the Wang Mang period (see fig. 5) and Tang writes that the moulds were baked. Tang also writes that the mother moulds were made larger than the size of the final coin, because the moulds shrinked after the heating (p. 75).
The mould from the Coole collection probably only still exists because it cracked during baking and was discarded.
Fig. 1-4 are Wu Zhu cluster moulds.
Fig. 5 is a coin mould baking kiln from the Wang Mang period.
Fig. 6 is a Wu Zhu tree shape mould.
Fig. 7 is a Ban Liang tree shaped mother mould.
Fig. 8 is a rubbing of a Wu Zhu mother mould.
Fig. 9 is a rubbing of a Wu Zhu tree shaped mould.
Fig. 10 is a Wang Mang spade mother mould.
Fig. 11 shows two stone moulds for direct casting of Da Quan Wu Shi and
knife coin of the Wang Mang period.
Fig. 12 is a drawing of what the coins would look like if they were intact when the mould was opened.