The composition of bell-metal varies considerably, as may be seen below:—
1. (Standard.) Copper, 78 parts; tin, 22 parts;[136] fused together and cast in the manner described under Bronze. The most sonorous of all the alloys of copper and tin. It is easily fusible, and has a fine compact grain, and a vitreous-conchoidal and yellowish-red fracture. According to Klaproth, the finest-toned Indian gongs have this composition.
[136] The resulting alloy probably contains 7 Cu + Sn.
2. (Founder’s Standard.) Copper, 77 parts; tin, 21 parts; antimony, 2 parts.[137] Slightly paler and inferior to No. 1.
[137] More antimony, or some other metal, is often added, as subsequently noticed; but always to the injury of the alloy as bell-metal.
3. Copper, 80 parts; tin, 20 parts.[138] Very deep-toned and sonorous. Used in China and India for the larger gongs, tam-tams, &c.
[138] Equal to about 8 Cu + Sn. In some gongs the proportion of tin is so low as 22, or even 20 parts, to 100 parts of copper.
4. Copper, 78 to 80 parts; tin, 22 to 20 parts. Usual composition of Chinese cymbals, tam-tams, &c.
5. Copper 75 (= 3) parts; tin, 25 (= 1) parts.[139] Somewhat brittle. In fracture, semi-vitreous and bluish-red. Used for church and other large bells.
[139] Nearly equal to 6 Cu + Sn.