Bell Foundries

Bells of substantial size are typically made in foundries, with bellfounding traditions dating back almost 4,000 years. In East Asia, technology progressed rapidly from clay pottery bells to cast metal bells and gongs centuries before Europeans. Metalcasting is the process of pouring molten (liquid) metal into a specially-crafted mold. When the melt cools and hardens, it retains the form of the mold to produce almost any shape imaginable with the strength and durability of solid metal. 

In the Middle Ages, bellmakers would often travel from village to village, bringing with them their know-how and skill to cast bells in molds near a cathedral or church. Building onsite furnaces in pits at the base of these structures solved a very practical issue: the monolithic weight and challenge of moving bells. Thousand-pound bells could be lifted from the pit directly into the tower, saving poor mules the burden of carting them across rough terrain. 

When connections and transportation between cities improved, bellmakers set up shop in dedicated facilities called foundries, allowing them to better control the extreme temperatures needed to melt metal and create long-lasting bells. In times of war, these foundries might have been relied upon to make cannon and weaponry, but while those needs have diminished, bellfounding remains.

View inside a bell foundry.

Foundries cast bells for all manner of installations: churches, schools, municipal buildings, clock towers, ships, trains, and even farms – roughly 300 different foundries are known to have operated on American soil. Bell foundries often regularly supply bell fittings and replacement parts, while further consulting on tower installations, inspections, ongoing maintenance, and historic bell restoration projects.

Where a bell was cast (the foundry) says a lot about how it was made. From the casting process to the composition of bronze, and from bell tuning to decoration, the imprint of the bellmaker is felt at every turn. Even the very shape of a bell can distinguish its provenance. Bellfounding is both an art and a science that relies on the history and tradition of its craft, while continuing to evolve and redefine its place in our society.

What is bronze?

Bells are often cast in bronze, an alloy (combination) of copper and tin. While the proportions have been experimented with for thousands of years, the generally-recognized best composition is 80% copper to 20% tin for a bronze of expansive resonance and appealing sound. This 4:1 ratio, called bell metal, comes together in a crystal lattice arrangement of atoms that creates a uniquely harmonious damping capacity (the bronze’s ability to absorb energy) and sound velocity, which is what makes the toll of a bell (and related instruments like cymbals) ripple across a neighborhood.

Different founders have different bell metal recipes to cast their own high-quality bells. Generally, increasing the amount of tin in the alloy increases the decay time of the bell strike, or the length of time a person on the ground can hear the bell ring. Percentages of tin content can vary from 20% to 26%. It is interesting to note that both copper and tin on their own are relatively soft metals that would deform quite easily on striking. However, when combined in an alloy, a bell with greater strength and elasticity can be created. This is crucial for increasing vibrations (resonance) and reducing cracks when the bell is forcefully struck. Over time, the alloy will slowly develop a rich and protective patina called verdigris that makes the bell more resistant to weathering and harmful oxidation.

How bells are made

The craft of casting bells is both a science and an art, requiring exact calculations and precision engineering combined with delicate finesse and design. To make a bell of lasting quality, bell foundries today follow similar methods to bellmakers a thousand years ago. Each has unique variations and stylistic differences, but the process to make a bell follows these general steps:

Design the bell

A bellmaker must first determine the size and shape requisite to achieve the desired resonance, further calculating the volume of molten bronze needed for the project.

Make a pattern

Two wooden templates called strickle boards are cut to shape, aligning with the curvature and dimensions of the outer and inner bell, to create consistent proportions and depth all around.

Style the bell

A model or false bell is crafted from stone or brick and swept with sand or loam by the strickle boards, with detailing features, figures, and inscriptions further defined in wax.

Construct the mold

After coating the false bell in fireproof clay and dried, the sand and wax are removed, leaving behind a mold of the final bell. A mold of the inside of the bell, called the core, is created similarly.

Cast the bell

The outer and inner molds are clamped together, creating a gap uniform in shape and thickness, and the assemblage is buried in a casting pit. The gap is then filled with molten bronze. 

Allow the bell to cool

Depending on the bell’s size, it may take several days or weeks for the molten bronze to cool evenly. If cooling happens too quickly, the bell is more susceptible to fracture or crack.

Tune

A circular lathe spins the bell and finely shaves metal from the inside until its ring corresponds to a desired pitch or tone.

Fit the clapper

A clapper of proportionate size and weight is cast and then fitted inside the bell. This is fastened with a metal link through pre-drilled holes in the top of the bell.

Install the bell

The bell is now ready to install in a bell tower or other location. This is often preceded by a blessing, consecration, or dedication ceremony.

All that’s left is to let it ring!

Recycling bells

Throughout history and continuing today, foundries will melt down and reuse remnants or pieces from old bells in new castings for more economic bell making, as both copper and tin can be rather costly. This practice is also a way of continuing the legacy of bells that have come before. For instance, if a bell is broken or damaged, it can be “preserved” by being integrated into the new bell.

Bell foundries are also pioneering ways to reduce their carbon footprint. By collecting and melting down scrap metal, experimenting with lighter castings, limiting energy consumption, and embracing new technology like 3D printing, foundries are both preserving the ancient bellmaking traditions while securing their place in the future.