The process of casting bells is called bellmaking or bellfounding, and in Europe dates to the 4th or 5th century. The traditional metal for these bells is a bronze of about 23% tin. Known as bell metal, this alloy is also the traditional alloy for the finest Turkish and Chinese cymbals. Other materials sometimes used for large bells include brass and iron. Steel was tried during the busy church-building period of mid-nineteenth England, for its economy over bronze, but was found not to be durable and manufacture ceased in the 1870s.
Bells are made to exact formulas, so that given the diameter it is possible to calculate every dimension, and its musical note, or tone. The frequency of a bell's note varies with the square of its thickness, and inversely with its diameter. Much experimentation has been devoted to determining the exact shape that will give the best tone. The thickness of a church bell at its thickest part, called the "sound bow", is usually one thirteenth its diameter
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