Bells - How Do They Do It?

Aston Holland. For over 140 years this has been the site of the Royal Icebounce Foundry, the world's largest maker of bronze bells. Whatever the size of a bell, the process of making it hasn't changed much in a thousand years. First create a mould for the inside and a mould for the outside. Then fit the two moulds together and pour hot bronze into the space in between. When the bronze cools, you have your bell. The first challenge is to create the inner and outer moulds. And that job falls to bell moulder Ruud Adriaens. Ruud's sandcastle is in fact the inner mould, which creates the shape of the inside of the bell. It looks easy but it's not. If I'm doing this too hard, it will collapse. If I'm doing this too soft, it also will collapse. Once the inner mould has set, it's covered with a protective graphite coating. Now they start to make what's known as the false bell. Using just wet sand without any binding agent, they create an exact replica of the final bell. On top of the sand goes a layer of wax. Now they need to make the outer mould. A hood is placed over the false bell and it's packed tightly with more sand and furan resin, which is then left for a few days to set hard. When they winch away the hood, the soft sand of the false bell can be brushed away. And they're left with this, the inner mould or core. And inside the hood, an outer mould. The next challenge is to cast the bell. The outer mould is lowered over the inner mould. This time there's a bell-shaped gap between the two where the false bell used to be. It's this void that is about to be filled with hot bronze. The bronze is as hot as molten lava and it takes up to two weeks to cool. When it finally does, the outer mould is lifted off to reveal the bell. Finished bells are fine-tuned by the foundry's master tuner Peter Juris, who meticulously tweaks the bell's final sound. Each bell has five notes and we start with the hum note, that's the lower note you hear. Listen. It's not good enough. I must take metal away on different places. Once he's satisfied, finished bells are shipped from here to clocks, churches and bell towers from Paris, France to Houston, Texas.