Direct lost-wax casting (roundel)
A casting method that produces a single bronze cast from a single wax model. On a wooden board (A), the design was sketched (B) and a temporary core of clay (C) was applied to areas to be depicted in high relief. A separating layer of cloth (D) was then laid over the entire surface. The cloth was coated with wax (E), which was sculpted into the finished design. The front was then invested in clay or plaster (F), inverted to remove the temporary core (G), and the back invested (H). After the model was prepared, the remaining steps to produce the bronze were similar to those described for indirect lost-wax casting.

Direct lost-wax casting (bust)
A casting method that produces a single bronze cast from a single wax model. A generalized core of clay or plaster (A) was prepared for the head and reinforced with iron wire (B). Wax (C) was applied and sculpted into the finished face and hair. The head was then placed on a temporary core of clay (D) for the chest, possibly prepared over a wooden form (E). The drapery and shoulders were modeled in wax (F), which slightly overlapped the wax edge of the head (G). Square iron pins (H) were inserted into the head to support the heavy core. Fine iron wires may have also been inserted into the chest (I) as core supports. The exterior was invested in clay or plaster (J), inverted to remove the temporary core in the chest (K), and the interior invested (L). After the model was prepared, the remaining steps to produce the bronze were similar to those described for indirect lost-wax casting.

Indirect Lost-wax Casting
A casting method that produces multiple bronzes from a single model. A wax model was prepared in the form of the desired bronze figure (A). A plaster piece mold would be prepared around the model, then disassembled and the model removed (B). The mold was reassembled, tightly bound, and used to cast a wax copy in several parts. For solid parts, the mold was filled with hot wax (C). For hollow parts, the wax was swirled inside the mold and the excess poured out (D). The remaining wax shell was filled with a mixture of plaster and sand, forming a core, and the wax with its core was then removed from the mold (E). The wax parts were joined and finished, and fine iron wires were inserted to secure the core (F). Channels were added to the wax model to allow the molten bronze to be poured in and gases to escape (G). This assembly was then encased in a plaster mixture (H). The plaster mold was heated and dried. The wax was melted out, leaving a void in the shape of the model, and the plaster core suspended inside by the iron wires (I). Molten bronze was poured in, surrounding the core and filling every part of the mold (J). The channels and core pins were removed from the cast and the surface was cleaned, chased, and polished (K).

Hercules, model created by 1496, cast possibly by 1496, bronze with gilding and silvering, The Frick Collection, New York, Gift of Miss Helen Clay Frick

Mold
A hollow form used to cast wax or bronze. Clay or plaster is applied to a positive model of the desired figure, creating a negative impression of the surface. A mold can be made of the entire model or created in sections (piece-mold).

Oil-gilding
A technique by which thin sheets of gold foil are adhered to the metal using a drying oil or resin. After application, the gold is carefully burnished to create a compact, highly reflective surface.

Antoninus Pius (detail), probably 1524, bronze with gilding and silvering, The Metropolitan Museum of Art, New York, Gift of Edward Fowles, 1965

Silvering
A technique for applying a thin layer of silver to the surface of a bronze. Certain silvering techniques parallel those described for fire-gilding and oil-gilding. Silver can also be plated onto the surface of a bronze by using chemical solutions.

Venus Felix (detail), model possibly by 1496, cast c. 1510, bronze with gilding and silvering, Kunsthistorisches Museum, Vienna, Kunstkammer