As a material for sculpture, bronze was first used in ancient Greece and Rome. African and Chinese people also used bronze to make various artworks. During the Middle Ages, artists used less bronze in casting whole sculptures. Instead, they were more likely to hammer thin pieces of bronze on top of wood. The sculpture "St. Peter", believed to be the work of Arnolfo di Cambio, is one of the largest and earliest recent cast bronze pieces. Starting again in the first part of the fifteenth century, artists once used bronze for casting. Artists like Ghiberti were expert at casting their work from bronze.
Today artists make bronzes from sand molds or from the "cire perdue" method. In sand molding bronze pieces, the artist takes the following steps: he makes a mold from the plaster model, inserts a core and then finishes the piece by pouring molten bronze into the cast.
The "cire perdue" method is less expensive to use because the model is a bit smaller than the mold that encloses it. The sculptor pours wax into the space between the two, and there are vent pipes at various points. When finished, the artist shapes the outer wax in the precise manner of the finished bronze piece; at that point the artist pours the molten bronze into the vent on the top; this melts the wax. The amount of wax that melts out determines the amount of bronze that the artist needs to use.
The "patina" of the bronze refers to the greenish tint and surface that happens when bronze ages and by the reaction of various chemicals; The patinas of bronze pieces done by the Ancient Greeks are an excellent example of how patina looks. Today, however, patina can be artificial; Epstein favored using this method.