BELL′-METAL

Syn. Æs CAMPANA′′RUM , L.; Métal de cloche , Fr.; Glockengut , Glockenspeise , Ger. The alloy, usually bronze, of which bells, ., are made. 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, . [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, . 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. 6. Copper, 80 parts; tin, 10 1 ⁄ 4 parts; zinc, 5 1 ⁄ 2 parts; lead, 4 1 ⁄ 4 parts. English bell-metal, according to Thomson. Inferior to the last; the lead being apt to form isolated drops, to the injury of the uniformity of the alloy. 7. Copper, 68, parts; tin, 32 parts. [140] Brittle; fracture conchoidal and ash-grey. Best proportions for house-bells, hand-bells, .; for which, however, 2 of copper, and 1 of tin, is commonly substituted by the founders. [140] Equal to about 4 Cu + Sn. 8. Copper, 72 parts; tin, 26 1 ⁄ 2 parts; iron, 1 1 ⁄ 2 part. Used by the Paris houses for the bells of small clocks or pendules. 9. Copper, 72 parts; tin, 26 parts; zinc, 2 parts. Used, like the last, for very small bells. 10. Copper, 70 parts; tin, 26 parts; zinc, 2 parts. Used for the bells of repeating watches. 11. Melt together copper, 100 parts; tin, 25 parts. After being cast into the required object, it should be made red hot, and then plunged immediately into cold water in order to impart to it the requisite degree of sonorousne . For cymbals and gongs. 12. Melt together copper, 80 parts; tin, 20 parts. When cold it has to be hammered out with frequent annealing. 13. Copper, 78 parts; tin, 22 parts. This is superior to the former, as it can be rolled out. For tom-toms and gongs. 14. Melt together copper, 72 parts; tin, 26 to 56 parts; iron, 1·44 part. Used in making the bells of pendules or ornamental Paris i an clocks. For clock-bells. Concluding remarks. Castings in bell-metal are all more or le brittle; and, when recent, have a colour varying from a dark ash-grey to greyish-white, which is darkest in the more cupreous varieties, in which it turns somewhat on the yellowish-red or bluish-red. The larger the proportion of copper in the alloy, the deeper and graver the tone of the bells formed of it. The addition of tin, iron, or zinc, causes them to give out their tones sharper. Bismuth and lead are also often added to modify the tone, which each metal affects differently. The addition of antimony and bismuth is frequently made by the founder to give a more crystalline grain to the alloy. All these additions are, however, prejudicial to the sonorousne of bells, and of very doubtful utility. Rapid refrigeration increases the sonorousne of all these alloys. Hence M. D’Arcet recommends the ‘pieces’ to be heated to a cherry-red after they are cast, and after having been suddenly plunged into cold water, to be submitted to well-regulated pre ure by skilful hammering, until they a ume their proper form; after which they are to be again heated and allowed to cool slowly in the air. This is the method adopted by the Chinese with their gongs, ., a casing of sheet-iron being employed by them to support and protect the pieces during the exposure to heat. In a general way, however, bells are formed and completed by simple casting. This is nece arily the case with all very large bells. Where the quality of their tones is the chief object sought after, the greatest care should be taken to use commercially pure copper. The presence of a very little lead or any similar metal greatly le ens the sonorousne of this alloy; whilst that of silver increases it. This last metal has been detected in many old church bells remarkable for the richne of their tones—articles of silver plate having been cast into the crucibles of the founders, as votive offerings, by the pious Christians of former ages. The specific gravity of a large bell is seldom uniform throughout its whole substance; nor can the sp. gr. from any given proportion of its constituent metals be exactly calculated owing to the many interfering circumstances. The nearer this uniformity is approached, or in other words, chemical combination is complete, the more durable and finer toned will be the bell. In general it is found nece ary to take about 1-10th more metal than the weight of the intended bell, or bells, in order to allow for waste and scorification during the operations of fusing and casting. See Bell , Bronze , Copper , .