BRONZE (probably from Lat. •s Brundisium, Brundisian copper). An alloy of two or more metals, the chief ingredient always being copper. with tin next in proportion. Often zinc and lead have been used but if zinc is in greater propor tion than tin, the result is not properly a bronze (see ALLOY), while lead is never present in large amounts. Silver has been found in the analysis of ancient bronzes, but this may have come from an imperfect smelting of the tin. The bronze tools found in ancient quarries in Egypt are said to consist of SS parts copper to 12 of tin. a hard alloy; but the supposes] greater hardness which would have enabled stone-cutte•s to work with them may have been produced by hammering, al though it has been suggested that phosphorus was used and has since disappeared. (See the paragraph treating phosphor-bronze. under AL LOY.) The famous mixture of antiquity called Corinthian bronze probably gained the brilliant color for which it was praised from a combina tion of copper and tin, in some such proportion as 90 of copper to 10 of tin, without other admix ture.
Bronze is peculiar in this, that the alloy shrinks and occupies much less space than the aggregate of the separate metals. Probably because of this shrinking, involving some interpenetration of the atoms, it is harder than either eoppe• or tin. and in this respect compares with zinc. Of course it
is vastly harder than lead. It ha. the peculiarity of filling the mold perfectly, because when melted it is very fluid—much more so than copper by it self. Bronze is easy to work with the tool. If used in thin sheets it is one of the best metal', for re pouss(' work, yielding regularly and evenly, and taking from the chasing-tool a beautiful and last ing finish. It takes from exposure to the weather, and especially to the earth in which it may be buried, a singularly beautiful green or greenish blue color and a slightly powdery texture, which constitutes what the ancients called the writ go vobilis, and which is spoken of by the modern stu dent as the I•rugo or patina. It is possible to anticipate the action of such natural causes, and to give to the surface of the bronze an artificial color, as by the use of a 'pickle,' or by exposing it when red-hot to certain vapors. Thus. a jet bl•ck patina is obtained by sulphur-fumes. The Japanese and Chinese produce ornamental bronzes, especially vases. platters, and the like, which are colored in clouded, mottled, and veined combina tions, sometimes of vivid red with different shades of brown and of yellow. Sometimes these care fully prepared decorations of the surface produce an effect similar to that of crystallization.