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Bronze vessel manufacturing technologies

Updated: Mar 22, 2019 Print

Piece-mould casting

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Diagram showing how an early Chinese bronze was formed [Photo/depts.washington.edu]

The primary technique for manufacturing bronze vessels during the Shang and Zhou dynasties (c.16th century-256 BC) was the piece-mould casting technique:

The first step is to create a clay model of the bronze vessel-to-be. The process of making a clay model is exactly the same as making a pottery vessel of certain shape and with certain decorative motifs. Then soft clay is pressed against it so as to acquire the negative impression of the model's shape and the decoration. Before the clay model becomes hardened, a layer of clay needs to be shaved off from it - the thickness of the shaved layer equals that of the wall of the bronze vessel-to-be. The model with a layer shaved off is known as the "core". The clay paste (as it gets half-hardened) is removed in sections, baked in slow heat and then dried in shade. These clay sections are called "piece moulds".

The piece moulds are assembled around the core, with both components fixed firmly in place. Then molten bronze is poured in the space between the core and the joined piece moulds. After the bronze cools, the piece moulds and the core are removed. After clearing and polishing, the bronze vessel is completed.  


Lost-wax casting

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Bronze ware with intricate decorative patterns manufactued by lost-wax casting technology[Photo/IC]

Archaeological research establishes that the lost-wax casting technique of bronze vessels was adopted by Chinese people in the mid or late Spring and Autumn Period (770-476 BC).

Lost-wax casting is also known as melt-model casting (rongmu fa). It involves fashioning a model of the bronze vessel-to-be from wax, which is then coated with wet clay paste (the thickness of the paste determines that of the wall of the desired bronze vessel). The clay paste becomes the clay mould after it dries. Fire-resistant material is applied to a hole that has been pierced in the clay mould beforehand. The wax model melts as the clay mould is heated, and is poured out from the clay mould to hollow it. The mould is strengthened after being fired in the kiln, and is then buried in sand where molten bronze liquid is poured into the hole. After cooling and solidifying, the mould is removed and the bronze vessel is ready for use. 



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