Bellfounding
Encyclopedia
Bellfounding is the casting of bells
in a foundry
for use in churches, clocks, and public buildings. A practitioner of the craft is called a bellmaker or bellfounder. The process in Europe dates to the 4th or 5th century. In early times, when a town produced a bell it was a momentous occasion in which the whole community would participate. Archaeological excavations of churchyard
s in Britain have revealed furnace
s, which suggests that bells were often cast on site in pits dug in the building grounds. In some instances bells were cast directly in the church. Before the nineteenth century, bellfounders tended to be itinerant, traveling from church to church to cast bells on site. It wasn't until the creation of railroads, that more centralized foundries were established. There are however examples of foundries producing bells prior to this, such as the Whitechapel Bell Foundry
.
Bells intending to be rung are usually made by casting bell metal
(a high-copper
bronze
alloy) of a size appropriate for the pitch
the bell is intended to produce. Fine tuning
of metal bells is achieved on a lathe
where a precise amount of material is removed from the inside of the bell in order to produce a true tone with correct harmonics
. Bells are used often to play a chime
sequence and so must be well tuned in order to produce a correct scale of musical notes.
. Portable bells came to Britain with the spread of Celtic Christianity
, and most of these still remaining share an association with Scotland, Wales and Ireland. Bells
are traditionally cast in foundries for use in churches, clocks, and public buildings. A practitioner of the craft is called a bellfounder or bellmaker.
and throughout the early mediæval
period and in centuries following, it was carried out predominantly by monks. Large bells in England are mentioned by Bede
as early as 670 A.D, and by the seventh or eighth century the use of bells had become incorporated into church services. Nearly 200 years later, in the tenth century is the first record of a complete peal of bells
. The chronologies of the abbot Ingulf suggest that Thurcytel
, the first Abbot of Crowland
, presented the Abbey with a bell named Guthlac, after which his successor, Egelric the Elder cast an additional six bells—two large, two of medium size and two small— to complete a peal of seven. The same period saw other ecclesiastics involved in the founding of bells. St. Dunstan, “The Chief of Monks”, was an expert worker in metals and known bell caster. Two bells were cast under his direction at Abingdon which also held two others cast by St. Ethelwold
. Methods of moulding by lost-wax casting were described by the thirteenth century Benedictine monk Walter de Odyngton
of Evesham Abbey.
Bellfounding as a regular trade followed later, which saw independent craftsmen set up small, permanent foundries in towns. Although these attracted a steady trade from the surrounding countryside, Mediæval founders did not confined themselves solely to bellmaking as their only source of livelihood. Instead, they often combined it with related trades, such as metal ware, utensil manufacturing and gunmaking. Some founders were itinerant, traveling from church to church to cast bells on site; but the majority had settled works in large towns. Among other places London, Gloucester, Salisbury, Bury St Edmunds, Norwich, and Colchester were seats of eminent foundries.
These early bells had tonal discrepancies; a result of their weight and alloy composition as well as uniform thickness and profile—where the height was disproportionate to the diameter. The next century brought advances in all aspects of bellfounding where a better understanding of principles of bell design contributed to the introduction of a superior shape. The angles at the crown and soundbow were gradually flattened out and the waist became shorter, flaring toward the mouth. Although tuning methods were still uncertain and empirical, sets of bells in diatonic sequence were installed at important parish churches and monasteries.
Archaeological excavations of churchyard
s in Britain have revealed furnace
s, which suggests that bells were often cast on site in pits dug in the building grounds. Great Tom of Lincoln Cathedral
was cast in the Minster yard in 1610, and the great bell of Canterbury
in the Cathedral yard in 1762. When the casting was complete, a tower was built over the casting pit, and the bell raised directly up into the tower. In some instances, such as in Kirkby Malzeard
and Haddenham
the bells were actually cast in the church.
Bellfounding is a process that in Europe dates to the 4th or 5th century. In early times, when a town produced a bell it was a momentous occasion in which the whole community would participate.
of bronze
. Much experimentation with composition has existed throughout history; the bells of Henry II had nearly twice as much copper
as tin
, while much earlier Assyrian bronze bells had ten times the amount of copper to tin. The recognized best composition for bell metal though is a ratio of approximately 80 percent copper and 20 percent tin. Bell metal of these ratios has been used for more than 3,000 years, and is known for its resonance
and "attractive sound." Both tin and copper are relatively soft metals that will deform on striking by alloying the two elements a harder and more rigid metal is created but also one with more elasticity than the use of one of the metals alone. This allows for a better bell resonance and causes the bell to "vibrate like a spring when struck", a necessary quality as the clapper may strike the bell at speeds of up to 600 miles per hour. The forces holding the tin and copper together cause vibrations rather than cracks when the bell is struck which creates a resonant tone. This metal combination also results in a tough, long-wearing material that is resistant to oxidation and subject only to an initial surface weathering
. Verdigris
forms a protective patina
on the surface of the bell which coats it against further oxidation.
The hardest and strongest bronze contains large amounts of tin and little lead though an alloy with more than 25% tin will have a low melting point and become brittle and susceptible to cracking. This low melting point proved to be the nemesis of Russia's third attempt at casting the Tsar Bell from 1733–1735. 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. Burning timber fell into the casting pit and the decision was whether to let it burn and risk melting the bell, or to pour water on it and risk causing it cracking from cooling it too quickly. The latter risk was chosen and, as feared, because of the low melting point of the bronze and uneven cooling, the bell was damaged. The present bell is sometimes referred to as Kolokol III (Bell III), because it is the third recasting; remnants from the old bell were melted down and the metal re-used to cast the new bell. This practice was fairly commonplace, as the metal materials were very costly. Bell metal was considered so valuable that the first bronze coins for England were made in France out of melted down old bells.
or 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. They have also been made of glass, and though bells of this type produced a successful tone, this substance being very brittle was unable to withstand the continued use of the clapper.
By popular tradition the bell metal contained gold
and silver
, as component parts of the alloy, as it is recorded that rich and devout people threw coins into the furnace when bells were cast in the churchyard. The practice was believed to improve the tone of the bell. This however is likely erroneous and must be discredited 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. If used to any great extent, the addition would injure the tone not improve it. Small quantities of other metals found in old bell metal are likely impurities in the metals used to form the alloy.
Decorative bells can be made of such materials as horn, wood, and clay.
, clamped to a base-plate. Though the process does have some variations the major differences are in the quality control standards.
, stone
or brick
. It is then covered first with sand
or loam
sometimes 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.
The false bell is then covered with molten
wax and figures and inscriptions, also made of wax, applied on top by hand. The false bell is painted over with three coats of fireproof clay and then enclosed by a steel
mantle
overcasing. The empty space between the false bell and the mantle is filled in with cement and left to harden before the mantle is lifted off. The false bell is chipped away from the inner core to leave just the wax and cement. Any leftover scraps of the false bell are removed with a blow torch. The mold is then set over a coke fire to melt the remaining wax and to evaporate any water that has accumulated.
A model of the inner bell is then constructed of stone and coated with fireproof cement. It is then smoothed to remove any irregularities.
s of the bell case. The core plate is unclamped and the core broken out. The bell is then carefully extracted from the case. At this stage, any remaining loam still adhered to the bell is brushed away and flash (excess metal), which may have formed below the bell rim— owing to mould contraction in the presence of hot metal— is fettled off. This completes the casting process.
, with the frequency
of a bell's note varying with the square of its thickness, and inversely with its diameter. The thickness of a church bell at its thickest part (the "sound bow") is usually one thirteenth its diameter. If the bell is mounted as cast, without additional tuning after founding, it is called a "maiden bell". Russian bells are treated in this way and cast for a certain tone. "Tuned bells", which were common practice in Britain and Europe, are worked after casting to produce a precise note.
In the early days of bellfounding, bells were tuned using an imprecise method whereby the inside of the bell, or the edge of the lip, was chipped away. With the improvement of machinery, this was done using a lathe. The bell is cast with slightly thicker sides before being inverted, and gripped by vises, to keep it perfectly firm. The bell is then ground as it rotates on a circular lathe
to acquire the precise tone. The bell tuner must be highly skilled as it takes years of experience to know how much metal to remove. By this means, bells can be very accurately tuned.
In casting, bells are best left sharp, for flattening injures the tone much less than sharpening. A bell may readily be flattened one-eighth of a tone, or even more, but it cannot be sharpened so much; indeed, any sharpening is to be deprecated, and if at all possible should be avoided. The bell tone is tested frequently during the tuning process usually with tuning forks or an electronic stroboscopic tuning device commonly called a Strobe tuner which registers the vibrations as the bell is struck. If the tone is too low, the lathe operator grinds more metal off the lower edge of the bell. If the tone is too high, the bell is thinned with a file. The bell's strongest harmonic
s are tuned to be at octave
intervals
below the nominal note, but other notes also need to be brought into their proper relationship.
Bell (instrument)
A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually a hollow, cup-shaped object, which resonates upon being struck...
in a foundry
Foundry
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools. The most common metals processed are aluminum and cast iron...
for use in churches, clocks, and public buildings. A practitioner of the craft is called a bellmaker or bellfounder. The process in Europe dates to the 4th or 5th century. In early times, when a town produced a bell it was a momentous occasion in which the whole community would participate. Archaeological excavations of churchyard
Churchyard
A churchyard is a patch of land adjoining or surrounding a church which is usually owned by the relevant church or local parish itself. In the Scots language or Northern English language this can also be known as a kirkyard or kirkyaird....
s in Britain have revealed furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...
s, which suggests that bells were often cast on site in pits dug in the building grounds. In some instances bells were cast directly in the church. Before the nineteenth century, bellfounders tended to be itinerant, traveling from church to church to cast bells on site. It wasn't until the creation of railroads, that more centralized foundries were established. There are however examples of foundries producing bells prior to this, such as the Whitechapel Bell Foundry
Whitechapel Bell Foundry
The Whitechapel Bell Foundry is a bell foundry in Whitechapel in the London Borough of Tower Hamlets, in the East End of London. The foundry is listed by the Guinness Book of Records as the oldest manufacturing company in Great Britain...
.
Bells intending to be rung are usually made by casting bell metal
Bell metal
Bell metal is a hard alloy used for making bells. It is a form of bronze, usually approximately 4:1 ratio of copper to tin...
(a high-copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...
alloy) of a size appropriate for the pitch
Pitch (music)
Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...
the bell is intended to produce. Fine tuning
Musical tuning
In music, there are two common meanings for tuning:* Tuning practice, the act of tuning an instrument or voice.* Tuning systems, the various systems of pitches used to tune an instrument, and their theoretical bases.-Tuning practice:...
of metal bells is achieved on a lathe
Lathe
A lathe is a machine tool which rotates the workpiece on its axis to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.Lathes are used in woodturning,...
where a precise amount of material is removed from the inside of the bell in order to produce a true tone with correct harmonics
Harmonic series (music)
Pitched musical instruments are often based on an approximate harmonic oscillator such as a string or a column of air, which oscillates at numerous frequencies simultaneously. At these resonant frequencies, waves travel in both directions along the string or air column, reinforcing and canceling...
. Bells are used often to play a chime
Chime (bell instrument)
A carillon-like instrument with fewer than 23 bells is called a chime.American chimes usually have one to one and a half diatonic octaves. Many chimes play an automated piece of music. Prior to 1900, chime bells typically lacked dynamic variation and the inner tuning required to permit the use of...
sequence and so must be well tuned in order to produce a correct scale of musical notes.
History
Bellfounding has had an crucial role throughout the history of ancient civilizations. Eastern bells, known for their tremendous size, were some of the earliest bells, cast many centuries before the European Iron AgeIron Age
The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...
. Portable bells came to Britain with the spread of Celtic Christianity
Celtic Christianity
Celtic Christianity or Insular Christianity refers broadly to certain features of Christianity that were common, or held to be common, across the Celtic-speaking world during the Early Middle Ages...
, and most of these still remaining share an association with Scotland, Wales and Ireland. Bells
Bell (instrument)
A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually a hollow, cup-shaped object, which resonates upon being struck...
are traditionally cast in foundries for use in churches, clocks, and public buildings. A practitioner of the craft is called a bellfounder or bellmaker.
Britain
Bellfounding in Britain, as with other scientific crafts, had its origins with monasticismChristian monasticism
Christian monasticism is a practice which began to develop early in the history of the Christian Church, modeled upon scriptural examples and ideals, including those in the Old Testament, but not mandated as an institution in the scriptures. It has come to be regulated by religious rules Christian...
and throughout the early mediæval
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
period and in centuries following, it was carried out predominantly by monks. Large bells in England are mentioned by Bede
Bede
Bede , also referred to as Saint Bede or the Venerable Bede , was a monk at the Northumbrian monastery of Saint Peter at Monkwearmouth, today part of Sunderland, England, and of its companion monastery, Saint Paul's, in modern Jarrow , both in the Kingdom of Northumbria...
as early as 670 A.D, and by the seventh or eighth century the use of bells had become incorporated into church services. Nearly 200 years later, in the tenth century is the first record of a complete peal of bells
Ring of bells
"Ring of bells" is a term most often applied to a set of bells hung in the English style, typically for change ringing...
. The chronologies of the abbot Ingulf suggest that Thurcytel
Thurcytel
Thurcytel was abbot of Crowland and perhaps also of Bedford Abbey.Thurcytel of Crowland is known from the unreliable history of Crowland Abbey attributed to Pseudo-Ingulf, an account full of anachronisms including the claim that Thurcytel was Lord Chancellor of England...
, the first Abbot of Crowland
Abbot of Crowland
The Abbot of Crowland was the head of Crowland Abbey, an English monastery built up around the shrine of Saint Guthlac by King Æthelbald of Mercia, and refounded as a Benedictine house circa 948. The last abbot was John Wells , who handed the monastery over to royal control and dissolution in...
, presented the Abbey with a bell named Guthlac, after which his successor, Egelric the Elder cast an additional six bells—two large, two of medium size and two small— to complete a peal of seven. The same period saw other ecclesiastics involved in the founding of bells. St. Dunstan, “The Chief of Monks”, was an expert worker in metals and known bell caster. Two bells were cast under his direction at Abingdon which also held two others cast by St. Ethelwold
Æthelwold of Winchester
Æthelwold of Winchester , was Bishop of Winchester from 963 to 984 and one of the leaders of the tenth century monastic reform movement in Anglo-Saxon England....
. Methods of moulding by lost-wax casting were described by the thirteenth century Benedictine monk Walter de Odyngton
Walter Odington
Walter Odington was an 14th century English Benedictine scientific and especially musical theory author. He is also known as Walter of Evesham, by some writers confounded with Walter of Eynsham, who lived about fifty years earlier, died not earlier than 1330.During the first part of his religious...
of Evesham Abbey.
Bellfounding as a regular trade followed later, which saw independent craftsmen set up small, permanent foundries in towns. Although these attracted a steady trade from the surrounding countryside, Mediæval founders did not confined themselves solely to bellmaking as their only source of livelihood. Instead, they often combined it with related trades, such as metal ware, utensil manufacturing and gunmaking. Some founders were itinerant, traveling from church to church to cast bells on site; but the majority had settled works in large towns. Among other places London, Gloucester, Salisbury, Bury St Edmunds, Norwich, and Colchester were seats of eminent foundries.
These early bells had tonal discrepancies; a result of their weight and alloy composition as well as uniform thickness and profile—where the height was disproportionate to the diameter. The next century brought advances in all aspects of bellfounding where a better understanding of principles of bell design contributed to the introduction of a superior shape. The angles at the crown and soundbow were gradually flattened out and the waist became shorter, flaring toward the mouth. Although tuning methods were still uncertain and empirical, sets of bells in diatonic sequence were installed at important parish churches and monasteries.
Archaeological excavations of churchyard
Churchyard
A churchyard is a patch of land adjoining or surrounding a church which is usually owned by the relevant church or local parish itself. In the Scots language or Northern English language this can also be known as a kirkyard or kirkyaird....
s in Britain have revealed furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...
s, which suggests that bells were often cast on site in pits dug in the building grounds. Great Tom of Lincoln Cathedral
Lincoln Cathedral
Lincoln Cathedral is a historic Anglican cathedral in Lincoln in England and seat of the Bishop of Lincoln in the Church of England. It was reputedly the tallest building in the world for 249 years . The central spire collapsed in 1549 and was not rebuilt...
was cast in the Minster yard in 1610, and the great bell of Canterbury
Canterbury Cathedral
Canterbury Cathedral in Canterbury, Kent, is one of the oldest and most famous Christian structures in England and forms part of a World Heritage Site....
in the Cathedral yard in 1762. When the casting was complete, a tower was built over the casting pit, and the bell raised directly up into the tower. In some instances, such as in Kirkby Malzeard
Kirkby Malzeard
Kirkby Malzeard is a village and civil parish in the Harrogate district of North Yorkshire, England.In recent years a creamery in the village was acquired by the Wensleydale Creamery, and Wensleydale cheese is now made there.-History:...
and Haddenham
Haddenham, Buckinghamshire
Haddenham is a large village and is also a civil parish within Aylesbury Vale district in Buckinghamshire, England. Its estimated population in 2011 is 8,385 It is about south-west of Aylesbury and north-east of Thame.-History:...
the bells were actually cast in the church.
Bellfounding is a process that in Europe dates to the 4th or 5th century. In early times, when a town produced a bell it was a momentous occasion in which the whole community would participate.
Materials
Bell metal
Functional bells, for the intention of producing sound, are usually made by casting bell metal, an alloyAlloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
of bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...
. Much experimentation with composition has existed throughout history; the bells of Henry II had nearly twice as much copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
as tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
, while much earlier Assyrian bronze bells had ten times the amount of copper to tin. The recognized best composition for bell metal though is a ratio of approximately 80 percent copper and 20 percent tin. Bell metal of these ratios has been used for more than 3,000 years, and is known for its resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
and "attractive sound." Both tin and copper are relatively soft metals that will deform on striking by alloying the two elements a harder and more rigid metal is created but also one with more elasticity than the use of one of the metals alone. This allows for a better bell resonance and causes the bell to "vibrate like a spring when struck", a necessary quality as the clapper may strike the bell at speeds of up to 600 miles per hour. The forces holding the tin and copper together cause vibrations rather than cracks when the bell is struck which creates a resonant tone. This metal combination also results in a tough, long-wearing material that is resistant to oxidation and subject only to an initial surface weathering
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
. Verdigris
Verdigris
Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over a period of time. It is usually a basic copper carbonate, but near the sea...
forms a protective patina
Patina
Patina is a tarnish that forms on the surface of bronze and similar metals ; a sheen on wooden furniture produced by age, wear, and polishing; or any such acquired change of a surface through age and exposure...
on the surface of the bell which coats it against further oxidation.
The hardest and strongest bronze contains large amounts of tin and little lead though an alloy with more than 25% tin will have a low melting point and become brittle and susceptible to cracking. This low melting point proved to be the nemesis of Russia's third attempt at casting the Tsar Bell from 1733–1735. The bell was never rung, and a huge slab cracked off (11.5 tons) during a fire in the Kremlin
Kremlin
A kremlin , same root as in kremen is a major fortified central complex found in historic Russian cities. This word is often used to refer to the best-known one, the Moscow Kremlin, or metonymically to the government that is based there...
in 1737 before it could ever be raised from its casting pit. Burning timber fell into the casting pit and the decision was whether to let it burn and risk melting the bell, or to pour water on it and risk causing it cracking from cooling it too quickly. The latter risk was chosen and, as feared, because of the low melting point of the bronze and uneven cooling, the bell was damaged. The present bell is sometimes referred to as Kolokol III (Bell III), because it is the third recasting; remnants from the old bell were melted down and the metal re-used to cast the new bell. This practice was fairly commonplace, as the metal materials were very costly. Bell metal was considered so valuable that the first bronze coins for England were made in France out of melted down old bells.
Other metals
Other materials occasionally used for bell casting are brassBrass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
or iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
. 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. They have also been made of glass, and though bells of this type produced a successful tone, this substance being very brittle was unable to withstand the continued use of the clapper.
By popular tradition the bell metal contained gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
and silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
, as component parts of the alloy, as it is recorded that rich and devout people threw coins into the furnace when bells were cast in the churchyard. The practice was believed to improve the tone of the bell. This however is likely erroneous and must be discredited 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. If used to any great extent, the addition would injure the tone not improve it. Small quantities of other metals found in old bell metal are likely impurities in the metals used to form the alloy.
Decorative bells can be made of such materials as horn, wood, and clay.
Manufacturing process
The craft of casting bells has remained essentially the same since the 12th century, being cast mouth down, in a two-part mould consisting of the core, and the shell, or copeCope
The cope is a liturgical vestment, a very long mantle or cloak, open in front and fastened at the breast with a band or clasp. It may be of any liturgical colour....
, clamped to a base-plate. Though the process does have some variations the major differences are in the quality control standards.
Measurement and templating
Firstly the bell design is calculated to precise specifications where the bellmaker determines the shape that the bell will need to take in order to resonate with the proper number of vibrations and create the right sound and pitch. The bell pattern is then cut out in two wooden templates called "strickle boards". One of the boards matches the dimensions of the outer bell (called the case or cope); the other matches that of the inner bell (called the core). The boards are used to create the inner and outer molds of the final bell.Constructing the mold
An exact stone model of the outer bell, sometimes called a false bell, is built on a base-plate using porous materials such as cokeCoke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
, stone
STONe
is a Japanese manga written and illustrated by Sin-Ichi Hiromoto. Kodansha released the two bound volumes of the manga on April 23, 2002 and August 23, 2002, respectively.The manga is licensed for an English-languague released in North America be Tokyopop...
or brick
Brick
A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...
. It is then covered first with sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
or loam
Loam
Loam is soil composed of sand, silt, and clay in relatively even concentration . Loam soils generally contain more nutrients and humus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils...
sometimes 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.
The false bell is then covered with molten
Mölten
Mölten is a comune in South Tyrol in the Italian region Trentino-Alto Adige/Südtirol, located about 60 km north of Trento and about 12 km northwest of Bolzano .-Geography:...
wax and figures and inscriptions, also made of wax, applied on top by hand. The false bell is painted over with three coats of fireproof clay and then enclosed by a steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
mantle
Gas mantle
An incandescent gas mantle, gas mantle, or Welsbach mantle is a device for generating bright white light when heated by a flame. The name refers to its original heat source, existing gas lights, which filled the streets of Europe and North America in the late 19th century, mantle referring to the...
overcasing. The empty space between the false bell and the mantle is filled in with cement and left to harden before the mantle is lifted off. The false bell is chipped away from the inner core to leave just the wax and cement. Any leftover scraps of the false bell are removed with a blow torch. The mold is then set over a coke fire to melt the remaining wax and to evaporate any water that has accumulated.
A model of the inner bell is then constructed of stone and coated with fireproof cement. It is then smoothed to remove any irregularities.
Casting the bell
After the outer steel mantle has been cleaned, it is again lowered over the outer bell model. The mantle and the outer bell mold are then lowered over the inner mold and the outer and inner sections are clamped together, leaving a space between them. The clamped mold is supported, by being buried in a casting pit which bears the weight of metal and allows even cooling. Ingots of bronze are melted in oil burners and heated until molten at a temperature of approximately 1566°F (870°C). The liquid metal is then skimmed to remove impurities before being transferred to drums. The drums are lifted over the pit and carefully tipped so that the hot metal flows into the space between the two molds. Holes in the top of the mantle insure that gases are able to escape. If gas remained in the metal, the bell would be too porous and be susceptible to cracking. This similar porousness can also develop if the mold is damp, not of the proper temperature, or if the metal is poured before it is hot enough. The bell is allowed to cool for several days. Large bells can take over a week to cool completely. Small bells, those under 500 pounds (227 kg), can be removed from the molding pit the following day.Cooling
After the bell and equipment has cooled completely, the mould, containing the newly cast bell, is raised from the pit by the projecting trunnionTrunnion
A trunnion is a cylindrical protrusion used as a mounting and/or pivoting point. In a cannon, the trunnions are two projections cast just forward of the centre of mass of the cannon and fixed to a two-wheeled movable gun carriage...
s of the bell case. The core plate is unclamped and the core broken out. The bell is then carefully extracted from the case. At this stage, any remaining loam still adhered to the bell is brushed away and flash (excess metal), which may have formed below the bell rim— owing to mould contraction in the presence of hot metal— is fettled off. This completes the casting process.
Tuning
Bells are manufactured with exact formulas, so that using the diameter it is possible to calculate precisely every dimension of the bell, and in turn its musical note, or tone. Much experimentation and testing has been devoted to determining the exact shape that will resonate the best tone. In general, the smaller the bell the higher the pitchPitch (music)
Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...
, with the frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of a bell's note varying with the square of its thickness, and inversely with its diameter. The thickness of a church bell at its thickest part (the "sound bow") is usually one thirteenth its diameter. If the bell is mounted as cast, without additional tuning after founding, it is called a "maiden bell". Russian bells are treated in this way and cast for a certain tone. "Tuned bells", which were common practice in Britain and Europe, are worked after casting to produce a precise note.
In the early days of bellfounding, bells were tuned using an imprecise method whereby the inside of the bell, or the edge of the lip, was chipped away. With the improvement of machinery, this was done using a lathe. The bell is cast with slightly thicker sides before being inverted, and gripped by vises, to keep it perfectly firm. The bell is then ground as it rotates on a circular lathe
Lathe
A lathe is a machine tool which rotates the workpiece on its axis to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.Lathes are used in woodturning,...
to acquire the precise tone. The bell tuner must be highly skilled as it takes years of experience to know how much metal to remove. By this means, bells can be very accurately tuned.
In casting, bells are best left sharp, for flattening injures the tone much less than sharpening. A bell may readily be flattened one-eighth of a tone, or even more, but it cannot be sharpened so much; indeed, any sharpening is to be deprecated, and if at all possible should be avoided. The bell tone is tested frequently during the tuning process usually with tuning forks or an electronic stroboscopic tuning device commonly called a Strobe tuner which registers the vibrations as the bell is struck. If the tone is too low, the lathe operator grinds more metal off the lower edge of the bell. If the tone is too high, the bell is thinned with a file. The bell's strongest harmonic
Harmonic
A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental...
s are tuned to be at octave
Octave
In music, an octave is the interval between one musical pitch and another with half or double its frequency. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems"...
intervals
Interval (music)
In music theory, an interval is a combination of two notes, or the ratio between their frequencies. Two-note combinations are also called dyads...
below the nominal note, but other notes also need to be brought into their proper relationship.