Nobody Casts Bells Like This Anymore!

For over two centuries, the bells hanging in Germany's church towers were cast by hand using sand, fire and 4,000 kilograms of bronze. In today's Aged Skills History episode, we travel to Saarburg, where the Mabellon foundry completes a five-bell commission the same way since 1770. A craft so precise, so unforgiving, that a single mistake cannot be undone. The critical work week has begun. The moulds need to be taken apart and readied for the pour. With the crown already lifted off, the crane raises the cope clear. The grease layer does its job. The heavy cope pulls away from the false bell without any trouble. Chalked onto the cope is the number four in a diamond shape. The numbers on the moulds set the casting order. This will be the fourth bell poured. The diamond marks the front face of the bell, where the inscription appears. The crowns are set aside. The false bell has done its job. Hans Hein breaks away the loam mould. The graphite coating on the core lets it come off cleanly. The loam cannot be reused. Working side by side, the team thoroughly cleans both the cope and the core using hand brushes and a compressed air nozzle to remove every trace of dust. The inside of the core is then braced with iron cross-stays. These are packed with alternating layers of earth and sand. Inside this core filling, at the exact point where the clapper will hang, a suspension ring is put in place. It will be permanently cast into the crown of the bell's interior. The clapper suspension has to be positioned very accurately, so the clapper strikes the bell's strike ring right on target, producing a clean, resonant tone. Josef Merz brushes graphite over the inside face of the cope, paying close attention to the letter impressions that will form the inscription. The core gets the same graphite coating, a precaution to stop the molten metal from fusing to the mould surfaces. The first day of the casting week ends with the flaming of all the copes and the firing of all the cores for the Merzig set. The graphite layers need to dry out quickly, and the moulds should not go into the casting pit completely cold. With all the moulds prepared, assembly and burial can begin. Of the five bell set, the two largest moulds were built directly in the casting pit, where they stay. The team measures carefully to fit the remaining moulds into the available space. Large moulds are moved as little as possible to avoid damage. The three smaller bell moulds were built on the foundry floor and will be assembled inside the pit. Under the watchful eye of the master bell founder, Josef Merz and Hans Hein lower the core, whose construction was covered in the first part of this documentary, into the gravel pit. The core must sit perfectly level. Wooden wedges are driven in to get it exactly horizontal. The cope is then lowered onto the core, guided by the alignment holes marked on both parts before they were separated. The crown, along with its vent pipe assembly, must be seated with the same precision. The pouring hole and vent pipes are already plugged against dust. Josef Weyrich and his colleagues seal the joint between crown and cope with fresh loam. Once all the moulds are in position, the pit is filled back in with topsoil taken from a nearby stockpile. The fill goes in at 20 cm layers, and the number of completed layers is counted in chalk on the pit wall. As master founder Hermann explains, only pure topsoil is used. Under the intense heat of the pour, it sets as hard as concrete, stopping the casting pressure from pushing the ground upward. Layer by layer, the workers level the soil with a spade and pack it down with an electric tamper, burying all five bells takes three full days. After two and a half days, only the vent pipes still stick up above the surface. With the bells buried, the casting channels are laid. From the furnace, a casting bridge mounted at the tap hole of the metal chamber reaches out over the pit. On top of the filled pit, the team builds a brick channel system to carry the molten metal from the furnace to the moulds. Chalk lines drawn earlier mark the roots of the main runner and the individual branch channels. Since the bell founder can only fill one mould at a time, each branch channel is closed with an iron plate and opened one by one as the pour moves along. The channel walls need to be solid enough to handle the pressure of the molten metal and deep enough to hold a good head of material. The finished brickwork is lined with loam and then coated with graphite to keep the metal from burning into the channel walls. With the channels complete, the furnace is loaded. The Merzig set calls for a total of around 4,100 kilograms of material, known as bell metal. Its composition is set by the Limburg guidelines for the acoustic assessment of bells. All tone bells must be cast from genuine bell bronze, 78% copper and 22% tin, with no more than 2% of any foreign material allowed. Worker Kessler loads the calculated charge of bronze stock into the melting chamber. Describing the Saarburg furnace, Mr Marbellon explains, for bell casting we still use a flame furnace today. The furnace has two chambers, the combustion chamber on the left and the metal chamber on the right. We fire with Saar coal. The furnace was built for this specific fuel. As coal flame reaches its greatest heat right at the tip of the flame, to round off the overnight preparations, the workers light a small fire inside the channel system so the loam lining and graphite coating can fully cure before the pour the following afternoon. It is Friday morning, 110 days after the moulding work began. Smoke pouring from the foundry chimney confirms the furnace is well alight. The day's schedule is fixed down to the hour. Every hour and a half the men clear the fire grate, throw on fresh logs and add hundredweight loads of coal, until within five hours the metal reaches 1,150 degrees Celsius. In the furnace antechamber, the temperature climbs to around 2,000 degrees Celsius. Bell founders have no patron saint of their own. The Saarburg foundry has taken St Joseph as their own. His statue stands in a niche beside the furnace chimney. Every time a furnace is lit, large or small, two candles are burned in his honour. While we can adjust the metal at every stage of the pour, what happens inside the mould is still completely beyond our control, even today. That is where we need the help of St Joseph, so that the casting goes well. After the fourth charge of wood and coal, the time comes to add the tin and complete the copper tin alloy. The tin can be held back until just before pouring, because its melting point is much lower than that of copper. It is now five minutes to two. This charge will take us through to quarter past three. We will probably only need one more. The pour is always scheduled for a Friday. The reason is simple. Once the hot metal sets in the mould, it cools very slowly. Any vibration from outside during that time could ruin the whole job. Over the weekend, with no machinery running nearby, disturbances are at their lowest. Just before the pour, the metal bath is checked one last time and cleared of all slag and surface deposits. Palm branches blessed on Palm Sunday are then cast into the melt to bring God's blessing to the pour. Members of the parish congregation turn out in large numbers for the casting, led by their priest. The master bell founder taps the furnace. Metal streams into the main runner and is directed, branch by branch, to each of the five moulds in turn. Every worker has an assigned post. One skims slag from the surface, another pulls the iron plate from the next branch channel to release the flow. A third draws the plug from the pouring hole, so the bell bronze can fill the mould. Five days later, the bells of the Merzig set are brought out of the pit. Over the weekend, the castings cooled enough in their moulds for the team to take down the channel system on Monday and begin uncovering the bells one by one. Today, the last of the five comes out of the ground. In a matter of moments, Hans Hein will knock away the cope, built up over months of careful work, to reveal the newly cast bell inside. This moment is called the true birth of the bell. It comes into the light for the very first time, and months of work are about to be judged. Members of the Merzig congregation have come out to witness the birth of their bells. The bells are not yet fully cooled, still warm to the touch. Hans Hein knocks the core free from the bell's interior. The supports that held the sand bed for the clapper mounting are also cleared away. The clapper mounting ring is cast solidly into the crown of the bell's interior. A bell is a musical instrument, but it only speaks when its clapper strikes the rim. The Limburg guidelines require that no new bells leave the foundry for a parish without passing an official acceptance inspection. The bells must wait another three weeks before they are ready for that examination. The inspection is carried out by an assessor appointed by the responsible diocese, or for Protestant congregations, by the regional church authority. He evaluates both pitch and acoustic quality. The results go into the formal acceptance record. Working through a set sequence, the assessor strikes the bell with a purpose-made adjustable tuning fork, measuring the fundamental tone and each of the partial tones in turn. For the benefit of the film, the assessor invites the new set to ring out in full. With the inspection passed, the bells are cleared to leave the foundry for consecration and installation in the bell tower. First, the workers bring them to a high shine. During casting, a very thin layer of tin settles on the outer bell surface, leaving a bright silver sheen. The men work the surface with birch twig brooms, sand and water, drawing out the best possible silver finish without marking the metal. After 150 working days, the work speaks for itself.