The Cornille Havard foundry changed its manufacturing process in 2003: all bells are now cast upside down. This process has improved their metallurgical quality, musicality, and aesthetics. The bells are made of bronze, an alloy of copper (78%) and tin (22%). The metal is melted at 2,192°F (1,200°C) in a double-vaulted reverberatory furnace built in 1865. This furnace is used to cast bells weighing more than 500 kg. Before pouring, the bell moulds are buried in a pit. On top, a brick conduit allows the bronze to flow into the moulds.