Bellfounding

Bellfounding is the casting and tuning of large bronze bells in a foundry for use such as in churches, clock towers and public buildings, either to signify the time or an event, or as a musical carillon or chime.

In Britain, archaeological excavations have revealed traces of furnaces, showing that bells were often cast on site in pits in a church or its grounds.

Modern foundries produce harmonically tuned bells using principles established in the late 19th century; some of these are also highly decorative.

[3] Portable bells came to Britain with the spread of Celtic Christianity, and most of those still remaining share an association with Scotland, Wales and Ireland.

[6] Methods of moulding by lost-wax casting were described by the thirteenth-century Benedictine monk Walter de Odyngton of Evesham Abbey.

Independent craftsmen set up permanent foundries in towns, such as London, Gloucester, Salisbury, Bury St Edmunds, Norwich, and Colchester.

Although tuning methods were still uncertain and empirical, sets of bells in diatonic scales were installed at important parish churches and monasteries.

[7] Whilst most bell founders were men, some women were also part of the art, such as Johanna Hill who took over her husband's business, and then left it to her daughter.

[8][9] Archaeological excavations of churchyards in Britain have revealed furnaces, which suggests that bells were often cast on site in pits dug in the building grounds.

The Hemony Brothers are regarded as the first of the modern western bell-founders who used a scientific approach to casting the optimum shape and tuning bells to harmonic principles.

[14] This allows for a better resonance and causes the bell to "vibrate like a spring when struck", a necessary quality as the clapper may strike at speeds of up to 600 miles per hour[dubious – discuss].

The forces holding the tin and copper together cause vibrations rather than cracks when the bell is struck which creates a resonant tone.

[14] This metal combination also results in a tough, long-wearing material that is resistant to oxidation and subject only to an initial surface weathering.

[11][15] This low melting point proved to be the nemesis of Russia's third attempt at casting the Tsar Bell from 1733 to 1735.

[11] The bell was never rung, and a huge slab cracked off (11.5 tons) during a fire in the Kremlin in 1737 before it could ever be raised from its casting pit.

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.

[19] They have also been made of glass, but although bells of this type produced a successful tone, this substance being very brittle was unable to withstand the continued use of the clapper.

This however is probably erroneous as there are no authentic analyses of bell metal, ancient or modern, which show that gold or silver has ever been used as a component part of the alloy.

An exact model of the inner face of the bell is built on a base-plate using porous materials such as coke, stone, or brick.

It is then covered first with sand or loam (sometimes mixed with straw and horse manure) and clay to form a smooth profile.

The false bell is painted over with three coats of fireproof clay and then enclosed by a steel mantle overcasing.

The mould is then set over a coke fire to melt the remaining wax and evaporate any water that has accumulated.

The complete mould is sometimes in a casting pit which stabilises it and enables slower cooling, or above ground in open air, depending on the foundry's traditions.

[22] As the metal enters the mould, holes in the top of the mantle ensure that gases are able to escape, otherwise there would be a risk the bell would be porous and susceptible to cracking.

An initial assessment is made to arrive at an average pitch for the scale, as this is dependent on casting tolerances.