Bronze is an alloy of copper and tin. Other metals used for coin alloys in China could be lead and zinc.
The Chinese were masters of bronze casting techniques already in the Shang dynasty. They were able to cast high-quality weapons, tools, utensils and above all the large bronze tripods and sacrificial vessels. Coins were cast in moulds made of clay, stone, bronze or iron. These four materials were used by all later periods to make moulds, but the techniques were improved.

The Zhou dynasty. Many different types of coins were cast directly in moulds made of carved clay, stone or bronze. So-called mother moulds were used in the later part of this period.  

The Han dynasty. Only the mother mould technique was used. The Han did only cast round coins, but Wang Mang cast knife and spade coins.

The Tang dynasty. The mother coin technique and sand moulds were invented. The "lost wax" method was used for a period.

The Ming and the Qing dynasties. Coins were cast with a large proportion of zinc and were actually brass coins. According to Yang (p. 37) coins of the Ming dynasty contained ca. 50% copper, 41,5% zinc, 6,5% lead and 2% tin.