Editing Bell (section)

== Bellfounding ==
{{Main|Bellfounding}}

The process of casting bells is called [[bellfounding]], and in Europe dates to the 4th or 5th century.{{sfn|Milham|1944|pp=313–318}} The traditional metal for these bells is a [[bronze]] of about 23% [[tin]].{{sfn|Cubberly|1989|pp=15–38}} Known as ''[[bell metal]]'', this alloy is also the [[cymbal alloys|traditional alloy]] for the finest Turkish and Chinese [[cymbal]]s. Other materials sometimes used for large bells include [[brass]] and [[iron]]. Steel was tried during the busy church-building period of mid-19th-century England, because it was more economical than bronze, but was found not to be durable and manufacture ceased in the 1870s.{{sfn|Jennings|1988|p=8}}

===Casting===
Small bells were originally made with the [[lost wax process]] but large bells are cast mouth downwards by filling the air space in a two-part mould with molten metal. Such a mould has an outer section clamped to a base-plate on which an inner core has been constructed.{{sfn|Jennings|1988|pp=3, 10}}

The core is built on the base-plate using porous materials such as [[Coke (fuel)|coke]] or brick and then covered in [[loam]] well mixed with straw and horse manure. This is given a profile corresponding to the inside shape of the finished bell and dried with gentle heat. [[Graphite]] and [[Calcium carbonate#Industrial applications|whiting]] are applied to form the final, smooth surface.

The outside of the mould is made within a perforated cast-iron case, larger than the finished bell, containing the loam mixture which is shaped, dried and smoothed in the same way as the core. The case is inverted (mouth down), lowered over the core and clamped to the base plate. The clamped mould is supported, usually by being buried in a ''casting pit'' to bear the weight of metal and to allow even cooling.{{sfn|Jennings|1988|p=11}}

Historically, before rail or road transport of large bells was possible, a "bell pit" was often dug in the grounds of the building where the bell was to be installed. Molten bell metal is poured into the mould through a box lined with [[Sand casting#Molding box and materials|foundry sand]]. The founder would bring his casting tools to the site, and a furnace would be built next to the pit.

===Bell tuning===
[[File:Erfurt Bell.png|thumb|The principal harmonics of the [[Maria Gloriosa|Erfurt bell]] (1497){{sfn|Starmer|1902|p=32}} typical of a harmonically-tuned bell:{{efn|name=Hemony}} strike note is E, with hum note an octave below, minor third, fifth, nominal above, and major third and perfect fifth in the second octave]]

{{wide image|Jonathan Harvey - Winchester Cathedral bell spectrum.png|800px|Spectrum of the tenor bell of [[Winchester Cathedral]] as analyzed by [[Jonathan Harvey (composer)|Jonathan Harvey]] using [[Fast Fourier transform|FFT]]{{efn|name=Roads}} "The bell produces a secondary pitch (f') which lies outside that 'inharmonic series though it is clearly audible when the bell is struck, 'to curiously thrilling and disturbing effect.'"{{sfn | Downes | 2009 | p=22}} {{audio|Jonathan Harvey - Winchester Cathedral bell spectrum.mid|Play approximation}} The strike tone is [[middle C]], the hum tone an octave below.}}

Large bells are generally around 80% copper and 20% tin ([[bell metal]]), which has been found empirically to give the most pleasant tone. However, the tone of a bell is mostly due to its shape. A bell is regarded as having a good tone when it is "in tune with itself".{{sfn|Fuller-Maitland|1910|p=615}} In western bell founding, this is known as "harmonic tuning" of a bell, which results in the bell's strongest harmonics being in harmony with each other and the strike note. This produces the brightest and purest sound, which is the attractive sound of a good bell. Much effort has been expended over the centuries to find the shape which will produce the harmonically tuned bell.

The accompanying musical staves show the series of harmonics which are generated when a bell is struck. The [[Erfurt bell]] is notable that it although it is an old bell, it is harmonically tuned, but was not typical of its time. [[Pieter and François Hemony]] in the 17th century reliably cast many bells for carillons of unequalled quality of tuning for the time, but after their death, their guarded trade secrets were lost, and not until the 19th century were bells of comparable tuning quality cast. It was only in modern times that repeatable harmonic tuning using a known scientific basis was achieved. The main partials (or harmonics) of a well-tuned bell are:

* hum note (an octave below the named note)
* strike tone (also called tap note or named note)
* tierce (a minor third above named note)
* quint (a fifth above named note)
* nominal (an octave above named note)

Further, less-audible, harmonics include the major third and a perfect fifth in the second octave above the named note.

This quest by various founders over centuries of bell founding has resulted in the development of an optimum profile for casting each size of a bell to give true harmonic tuning. Although bells are cast to accurate patterns, variations in casting mean that a final tuning is necessary as the shape of the bell is critical in producing the desired strike note and associated harmonics. Tuning is undertaken by clamping the bell on a large rotating table and using a cutting tool to remove metal. This is an iterative process in which metal is removed from certain parts of the bell to change certain harmonics. This process was made possible historically by the use of tuning forks to find sympathetic resonance on specific parts of a bell for the harmonic being tuned, but today electronic [[Electronic tuner#Strobe tuner|strobe tuners]] are normally used. To tune the strike note, the nominal or the strike note are tuned; the effect is usually the same because the nominal is one of the main partials that determines the tone of the strike note.{{sfn | Fletcher | Rossing | 2008 | p=685|ps=: Cites Schoofs et al., 1987 for major-third bell.}} The thickness of a church bell at its thickest part, called the "sound bow", is usually one thirteenth its diameter. If the bell is mounted as cast, it is called a "maiden bell".{{sfn | Beach | Rines | 1907 | p=602}}{{sfn |Encyclopedia Americana| 1918 | p=477}}

====Major third bell====
The traditional harmonically tuned bell has a minor third as a main harmonic. On the theory that western music in major keys may sound better on bells with a major third as a harmonic, production of bells with major thirds was attempted in the 1980s. Scientists at the Technical University in Eindhoven, using computer modelling, produced bell profiles which were cast by the Eijsbouts Bellfoundry in the Netherlands.{{sfn | Beach | Rines | 1907 | p=602}} They were described as resembling old Coke bottles{{sfn|Douglas|2002}} in that they had a bulge around the middle;<ref name=maj3 /> In 1999 a design without the bulge was announced.{{sfn | Rossing | 2000 | p=139}} However, the major bell concept has found little favour; most bells cast today are almost universally minor third bells.