Sculptors have a number of techniques at their disposal. Carving involves removing stone or wood from a larger piece until it takes the desired shape. Casting is the process of creating a desired form by first creating a mold and then filing it with liquid material such as molten metal or plaster and allowing it to harden. Once the material is solid, the mold is removed. Modeling is the process of building up the desired form from a soft material such as clay or wax. Assemblage is the process of creating a sculpture from a variety of materials including paper, wood and textiles.
Sculptures work in a wide range of natural and man-made materials. Modelers work in clay, plaster, wax and papier-mache. Carvings are made in marble and other stones, wood, bone and even plastic and soap. Castings are made from bronze, lead and plaster. Assemblages are made from whatever materials the artist finds useful, including bits of wood, wire, sheet metal and everyday items.
The tools used in sculpture vary by material and type of sculpture. For example, a sculptor working on a carving might employ chisels, hammers, drills, saws, and gouges. Artists working in clay or wax typically create their work with their hands. An artist working on a bronze sculpture might utilize the lost wax process, where he builds a model of the sculpture out of plaster or clay and then coats it with wax, placed it in a mold, and heats the mold until the wax is "lost," or runs out. The artist pours molten metal into the space once filled with wax. After metal hardens, the artist breaks away the mold and removes the plaster model.
The ancient Greek sculptors of 5th and 4th centuries B.C are known for their depictions of idealized human beings made in bronze and marble. The ancient Romans copied idealized Greek sculptures but also created realistic human portraits. During the Middle Ages, mostly anonymous sculptors decorated the great Romanesque and Gothic cathedrals with sculptures depicting figures and scenes from the Bible. During the Renaissance, Florence, Italy became famous for hosting a number of important sculptors including Lorenzo Ghiberti, Donatello and the Della Robbia family. However, the most famous Renaissance sculptor is probably Michelangelo Buonaratti, whose work includes his depiction of the Virgin Mary and crucified Christ called the "Pieta," the Greco-Roman wine-god "Bacchus" and the 14-foot tall statue of the Biblical hero "David." Some famous modern sculptures include Pablo Picasso's "Head of a Bull, Metamorphosis," Joan Miro's "Caress of a Bird" and Henri Gaudier-Brzeka's "Hieratic Head of Ezra Pound."