Since 1599 the Grassmayr Bell Foundry in Innsbruck, Austria has been casting bronze bells ranging from small concert bells to iconic church bells weighing several tons. The Grassmayr family has carried on the bell making craft for 14 generations. This year the foundry set another record with the 25-ton bell nicknamed "Bucharest" (it is destined for the Redemption Cathedral in the capital of Romania) which is now the world’s largest swinging bell.
The 25 ton Bucharest Bell with some of the Grassmayr Foundry staff
The tone of each bell varies depending on the difference in thickness and curvature of the bell’s “rib”. A large bell can have a range of up to 3 octaves! The “skirt” where the tongue hits, is the thickest part of the bell’s body.
The bell making process takes months to complete and begins with the calculation of the rib’s dimensions and a contour template.
An inner mold that will shape the inside of the bell is made with brick and clay.
A clay “shirt” that fills the space the real bell will occupy is then applied to the mold. It contains embossed wax images and inscriptions that will be imprinted on the inside of the outer mold (the casing) and determine the outside look of the bell. The liquid bronze which is 80% copper and 20% tin, will put enormous pressure on the casing so it is encircled with multiple iron rings. The casing is raised, the clay “shirt” is broken away, the inner and outer molds are cleaned, fire-treated, and finally sealed together.
The workers dress in fireproof aprons, masks, and gloves to pour the 2000 F degree liquid bronze into the void between the outer and inner molds. Special air outlets prevent air bubbles from forming. The pouring itself takes less than 10 minutes followed by a waiting period of up to 3 weeks for the metal to fully cool.
Finally, the form is broken. Even when everything looks good on the outside, it's too early to celebrate. If the purity of the sound deviates more than 1/16 of a semitone, the foundry will melt the bell and re-cast it. It is because of this superior precision and pristine craftsmanship that the Grassmayr Bell Foundry receives many orders for making and restoring bells worldwide. Today their bells ring in more than 100 countries.