Bells

Last week I joined a party of U3A members who visited our local bell foundry see:  http://www.taylorbells.co.uk/.

I discovered that bells and their manufacture are both much more complicated than I'd previously imagined.

A bell has five notes and after being cast bells are tuned to get all five notes in the correct pitch. That is done by removing metal very carefully in selected places from the inside of the bell.

Tuning lowers the tone, so bells are cast to be sharp; if a bell is flat the only remedy is to melt the metal and recast.

Molten metal is heated to 1200 C and then poured into a mould made from a mixture of sand and horse manure. The mould is buried in sand to contain any leaks. Before casting the mould has to be dried in an oven, otherwise water in the mould will evaporate explosively when the hot metal is poured in. One such explosion, in another foundry, once killed fifteen people.  After casting the bell is left in the mould for several days to cool.

The metal used makes a great difference to the tone of the bell. Steel is particularly unsatisfactory and the alloy nearly always used is bronze - about 2/9 tin and the rest copper.