Bell metal

Bell metal is a hard alloy used for making bells and related instruments, such as cymbals. It is a form of bronze, usually in approximately a 4:1 ratio of copper to tin (e.g., 78% copper, 22% tin by mass).

In India, in the state of Assam, it is called kanh while in West Bengal and Odisha, kansa, and is used for cooking and eating utensils. Sarthebari in Barpeta district of Assam holds a unique place in the production of kanh utensils. In Assam, utensils of kanh have many religious uses and the most unusual utensils, bata and banbati, are used to give offerings and puja or to show respect to honored guests and dignitaries. Belaguntha in Ganjam district, Kantilo in Nayagarh, and Balakati near Bhubaneswar are well known for this craft in Odisha.

Most commonly, and as per its colloquial name, bell metal was used for the casting of bells (see Bellfounding). Functional bells, with the intention of producing sound, are usually made by casting bell metal, a high-copper alloy of bronze, with approximately a 4:1 ratio of copper to tin (78% copper, 22% tin). Both tin and copper are relatively soft metals that will deform on striking (though tin to a lesser extent than copper), but alloying the two elements creates a metal which is harder and less ductile and also one with more elasticity than the use of just one of the metals alone. This metal combination produces a tough, long-wearing material that is resistant to oxidation and subject only to an initial surface weathering. Verdigris forms a protective patina on the surface of the bell which coats it against further oxidation. Bell metal of these ratios has been used for more than 3,000 years, and is known for its resonance and "attractive sound." This allows for a better bell resonance and causes the bell to "vibrate like a spring when struck", a necessary quality as the clapper may strike the bell at speeds of up to 600 miles per hour. The forces holding the tin and copper together cause vibrations rather than cracks when the bell is struck which creates a resonant tone. The bronze alloy C91300 is typically cited as bell bronze.

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