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BELLS (Historical background & Casting Process)



Historical Backgroud

The first bells date from ca. 2000 BC in China. Thereafter they appeared in Egypt, Greece, and in the Roman Empire. Bells were known in Europe beginning in the fourth century AD Following the legalization of Christianity (Edict of Milan, 313 AD), the ecclesiastical use of bells gradually began to spread. As bells became larger, their use evolved as a device for sending signals over greater distances and became an ideal means for summoning religious adherents to worship. Under the reign of Charles the Great (late 8th/early 9th century) the use of bells in bell towers even became mandatory.

L ater, at the end of the 13th century, bells were connected to mechanical clocks and took on the function of marking time. A substantial demand for bells quickly developed. With the rise of town centers, civic uses were added to the traditional religious functions of bells while the number of bells per tower increased. In fact, bells became an important means of communication that provided daily rhythm for citizens of the Middle Ages and evolved into the musical heartbeat of our West-European society: the city bell sounds the hour; the fire bell warns the people of fire and other danger; another bell announces the opening and closing of the town gates; the work bell called the active population to work; the civic bell confirms the regulations of the city authorities.

 

Franse bewerking uit de 15de eeuw van "Horologium Sapientiae"
French drawing (15th century) of the "Horologium Sapientiae" of Heinrich Seuse (12th century). © Lannoo.

Hence, bells originally were purely functional; they were used as such well into the 19th century. The musical adaptation of tower bells only began in the second half of the 15th century. A real breakthrough for the carillon as a musical instrument was only possible once bell founders had completely mastered the technique of tuning bells.


Casting and tuning process

Originally, bells in Western Europe were made by monks and later by bell founders. Now, the bell founding process is more industrial. Nonetheless, the birth of a bell is a unique event each time.

A bell is cast in three stages: the core, the "false bell," and the mantle.
The core is made of brick, covered with neutral sand, and molded with a lathe. The lathe is a template, a wooden plank or a metal plate that turns on an axis and shapes the mold to the profile of the inner surface of the bell.

 

De gemetselde kern     De kern, voltooid en gevormd door de mal
The core, in bricks The core, shaped by a template

Once the core is finished (dried or baked), the "false bell" is molded around the core. It is called a false bell because it forms an exact copy of the bell that will be cast, temporarily taking the place of the future bell. The shape of this bell, made of sand, is also shaped with the help of a lathe. A layer of melted wax is spread over the surface of the false bell, upon which the ornamentation and inscriptions are fixed.

De valse klok
The false bell

 

Once the false bell is finished, the mantle is finally put in place: a thin layer of moist, fireproof clay is spread over the decorated false bell. After completely drying, several more layers are added until the clay is about 10 cm thick. The mantle is reinforced by a few metal rings.

Bovenop de valse klok is de mantel geplaatst
The mantle

The entire assembly is heated to melt away the wax layer of the false bell. Once cooled, the mantle is lifted up. The sand remnants of the false bell are uncovered. In the meantime, the ornamentation and inscriptions have been imprinted on the inside of the mantle. They form, as it were, the negative of a photo.

Binnenzijde van de mantel
The inner side of the mantle

The false bell has served its purpose and is removed. The mantle is once again placed over the core. In the place of the false bell there is now an empty space between the core and mantle that later will be filled with bronze. It is put in the casting pit with other bell molds. This pit is completely filled and firmly packed with sand. Meanwhile, bronze, in an alloy of 80% copper and 20% tin, is gradually melted in an oven and heated to a temperature of ca. 1100 Celsius. Once it reaches the correct temperature, the liquid bronze is poured into the space between the core and mantle, via brick channels or directly into the mold using a casting bucket. After gradually cooling, which can take as much as a week, the burnt molds are removed and the bronze bell is revealed.

Het gietproces
The casting process

After any imperfections from the casting are removed and the bell is polished, the tuning process begins. The size and profile of the bell determine its pitch: the heavier the bell, the lower the pitch; the lighter the bell, the higher the pitch. After the casting, however, the intonation is far from precise, so new bells always require tuning.

To comprehend this, an understanding of the composition of the sound of a bell is necessary. When a bell is rung, besides the fundamental pitch, a number of overtones are heard.
This is true of all other instruments, but the structure of the overtone series of a bell is completely different: the most important are the hum tone, the fundamental, the minor third, the fifth, and the octave. Because the bell is a sounding body, a complex pattern of vibrations over the entire surface, the overtones can be localized on the bell.

In previous centuries, the pitch of the overtones was corrected by ear with the help of a musical instrument or tuning fork. Electronic devices have been used for this purpose during the last 15 years. When particular overtones are determined to be wrong, the tuner makes corrections by removing metal from specific places on the inside of the bell. This is called the internal tuning of a bell. Bells must also be tuned with regard to each other.

 

Het stemmen van de klok
Tuning the bell

The most important bell founders in Flanders were: the De Leenknecht Van Harelbeke family (14th century), the Waghevens and the vanden Gheins of Mechelen (16th & 17th centuries), Melchior De Haze (17th century), Willem Witlockx, Alexius Jullien, Joris du Mery, and the vanden Gheyn family of Louvain (18th century), the Van Aerschodt family (19th & 20th centuries), the Michiels family in Doornik (Tournai)(end of 19th, 20th centuries), and finally the Sergeys family (20th century). Currently, bells are no longer being cast in Belgium.

© Pictures: Bellfoundery Eijsbouts, Netherlands

 

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