Statue of Isis

This gilded bronze statuette of Isis is a part of the USC archaeology research collection. It is an extraordinary piece in that much of the outer layer of gold is preserved. A close examination reveals a layer of gesso (powdered limestone or gypsum mixed with glue) underneath the gold. It is the gesso which adheres the gold to the bronze.

The bronze has been identified as a tin-bronze. The gesso, principally calcium carbonate, contains chalk and calcite. A staining test has determined the gesso also contains protein. This is consistent with the Egyptian practice of utilizing animal glue to create a protein bond to adhere gold to furniture and other objects. The statuette has been dated to approximately 1000-500 B.C.E.

The standard Egyptian technique of gilding stone and wood in this period was to apply gold leaf atop a layer of gesso. The gesso was then spread thinly over the metal, which oftentimes had been prepared or roughened to promote adhesion. Gilding on small-scale bronze statues was exceptionally rare. Egypt was the only country that had a long standing tradition of gilding small bronze sculpture. However, gilding over bronze was rare even in Egypt.

There is speculation that, since bronze was initially used for weaponry, the existent technology was imported from the Orient or from Syria. Yet with the history of infiltration into Egypt, it is little wonder that the technology was fully exploited and constantly improved upon. One method of bronze working is referred to as “cold working” of bronze or sphyrelaton. The bronze was annealed, which is to say that it was 1) brought to a red heat 2) cooled 3) hammered. This was a method used during the early period.

Another method, the lost wax method, is known to us in two basic forms. The direct method was a process in which the bronze was cast “directly” from the model. The direct process of hollow casting utilized a medium such as clay. The basic shape and core of the casting were covered with a layer of wax in the exact desired form of the statue. The indirect method utilized a mold of the model. In this method, a negative mold was made of the model. This model was not destroyed and could be re-used provided the mold could be opened.

Samos is the accepted birth place for Greek bronze sculpture. Some Egyptian bronzes found in Samos were highly elaborate bronze figures. These figures are thought to represent queens, goddesses, and dolls and actually, have moveable limbs. Although the exact purpose of these figures is unknown, they are amazingly detailed, with inlays of other materials as decoration.

In the classical world, bronze statuettes were gilded with gold foil. In this process, the gold foil was wrapped around the object and held in place by bending foil around the statue, by riveting the foil in place or by cutting grooves into the surface of the metal and then inserting the edges of gold foil into grooves which were then hammered closed.

In the process of leaf gilding, sheets of gold were laid directly on the bronze surface that had been spread with adhesive. The adhesive was probably animal glue made from skin and bones or albumin from eggs, milk or blood. Gold leaf is visible when the small squares overlap. This double thickness resulting from the overlap of leaf resists the wear of time better than other areas.

In the process of fire gilding, a technique widely used on silver in the Roman world, gold powder or gold leaf was dissolved in hot mercury. It was then placed in a thin leather bag and squeezed to remove excess mercury, which passed through the leather. The resulting mixture was then applied to the surface of a thoroughly cleaned, copper alloy object. The surface was rubbed to form a shiny silver colored surface. When the object was gently heated, a firmly bonded layer of gold was left on the object. A variation of this technique was to rub mercury over the copper alloy object and apply the gold leaf on top. The gold would be dissolved by the mercury. Upon gently heating the object, most of the mercury would evaporate.

Bianchi, Robert Steven. “Egyptian Metal Statuary of the Third Intermediate Period (Circa 1070 -656 B.C.), from Its Egyptian Antecedents to Its Samian Examples.” Small Bronze Sculpture From The Ancient World. A three day symposium held at the Getty Museum in March 1989.

Houser, Caroline. Greek Monumental Bronze Sculpture of the Fifth and Fourth Centuries B.C. New York & London: Garland Publishing, Inc., 1987.

Kyrieleis, Helmut. “Samos and Some Aspects of Archaic Greek Bronze Casting.” Small Bronze Sculpture From The Ancient World. A three day symposium held at the Getty Museum in March 1989.

Oddy, W. A., Crowell, M. R., Craddock, P. T., Hook, D. R. “The Gilding of Bronze Sculpture in the Classical World.” Small Bronze Sculpture From The Ancient World. A three day symposium held at the Getty Museum in March 1989.