duced to a minimum. 6 Greek bronzes which are so expertly chased and engraved must have been changed rather markedly from their cast form. It is possible to tell whether or not a bronze has been chased by examining the surface closely, since an unchased surface has a rather spongy quality even to the naked eye.
PATINA AND DECORATION: The natural color of the new bronze is a rich gold, rather lighter than a freshly minted penny. Modern taste prefers its bronze darker, to such an extent that most people today think of bronze as naturally dark brown. The high copper content of bronze makes it possible to give it a finish or patina in a greater variety of colors than can be achieved in any other metal. Copper compounds give many variations on blue, green, red, black and brown. These colors are gotten by treating the surface with various chemicals. Polychromatic effects may be obtained by treating parts of the sculpture with different chemicals.
Paduan and Florentine bronzes of the Renaissance were often painted with a so-called "lacquer" to give them a dark brown color. In many cases this "lacquer" has worn off, exposing the original golden surface. (Nos. 129, 140)
A favorite way of finishing and decorating bronzes has been gilding. In gilding many surfaces, gold leaf is fixed to the surface with some adhesive medium. Copper is particularly susceptible to fusing with gold, and the special process for gilding copper and bronze objects is called "fire gilding". This process, known in the Middle Ages and described by Cellini, was probably used in earlier times, as well as in the Orient. An amalgam of gold and mercury is made. This may be quite liquid or a stiff paste. Cellini recommends one part of gold to eight parts of quicksilver. The amalgam is then spread on the surface of the bronze and the object heated until the mercury evaporates, leaving the gold fused with the bronze surface which is then burnished.
Inlay is another type of surface enrichment used on bronzes. Silver, copper, electrum and other metals appear inlaid as borders, or emphasizing particular features of a figure. Metal is inlaid in grooves or small areas, with edges undercut in such a way as to bind the metal when it is hammered in. Niello is sometimes used to give a pattern in black against the natural gold background of the bronze. Brilliant colors appear in small areas which are hollowed out and filled with enamels. These polychromatic effects are particularly characteristic of Greek, Egyptian, and Mediaeval work at periods when sculpture was normally painted.
Theophilus, AN ESSAY UPON VARIOUS ARTS, translated R. Hendrie, London, 1847.
Cellini, THE TREATISES OF BENVENUTO CELLINI ON GOLDSMITHING AND SCULPTURE, London, 1898.
Lüer, Hermann, TECHNIK DER BRONZEPLASTIK, Leipzig, 1902.
Richter, G. M. A., GREEK, ETRUSCAN AND ROMAN BRONZES, New York, 1915.