Page 21 - Curriculum Visions Dynamic Book

Bell-making bronze
There is a wide range of specialised bronzes, each one having its own distinctive properties. Up to 12% tin is normally used in making a bronze, but up to 20% is used for bell-making bronze, which is little used for engineering. The brittleness of bell-making bronze makes the bells liable to crack. However, this disadvantage is outweighed by the particularly sonorous tones made by the metal.
 The famous Liberty Bell is kept in Philadelphia, Pennsylvania, USA. Bell metals like that used for the Liberty Bell contain
about 20–25% tin and are very hard, giving them the appropriate resonance. However, this also makes them very brittle.
The crack in the Liberty Bell is so bad that it cannot be rung.
porous: a material containing many small holes or cracks. Quite often the pores are connected, and liquids, such as water or oil, can move through them.
 An English bronze bell foundry at work in
the 18th century. The furnace can be seen in the background. The molten bronze was poured into
a mould and allowed to solidify before being taken out and filed, to shape and tune the bell.
Corrosion resistance
Silicon bronze is used in places where there is a great danger of corrosion, such as in a chemical works. This alloy contains up to 3% silicon. Bronzes made of alloys of aluminium and copper have similar properties.
 The Chinese, Romans and Greeks used bronze extensively for casting sculptures, and it is still used for
this purpose today, as shown by the Bucking Bronco statue from Denver, Colorado, USA, above. However, bronze is now considered to be too expensive and labour intensive to use in comparison with other alloys and metals available.
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