II.

Materials and Techniques

Sculpture can be made from almost any organic or inorganic substance. The processes specific to making sculpture date from antiquity and, up to the 20th century, underwent only minor variations. These processes can be classified according to materials—stone, metal, clay, and wood; the methods used are carving, modelling, and casting. In the 20th century the means available to the sculptor were extended by new techniques, such as welding and assemblage, and by new materials such as fibreglass and plastic.

Although sculpture has been popular with private buyers, its permanence and resilience have made it especially suitable as an art of public statement. Sculpture that we see today as independent work in museums was often made for an architectural context, for instance the Classical Greek carvings in the British Museum now sometimes known as the Elgin Marbles, which originally decorated the Athenian temple, the Parthenon (see Acropolis).

A.

Carving

A procedure dating from prehistoric times, carving is a time-consuming and painstaking process in which the artist subtracts, or cuts away, superfluous material until the desired form is reached. The material is usually hard and frequently weighty; generally, the design is compact and is governed by the nature of the material. For example, the narrow dimensions of the marble block used by Michelangelo to carve his David (1501-1504, Accademia, Florence) strongly affected the pose and restricted the figure's outward movement into space.

Various tools are used, depending on the material to be carved and the state to which the work has progressed. In the case of stone, the rough first cutting to achieve the general shape may be performed by an artisan assistant using sharp tools; then the sculptor continues the work of cutting and chiselling. As work progresses, less penetrating tools are used, such as a bow drill and a rasp; finishing touches are carried out with fine rasps; then by rubbing with pumice or sand, and—if a great degree of smoothness is desired—by adding a transparent patina, made with an oil or wax base.

Just as the work of the painter is frequently dependent on preliminary drawings so the process of carving is often preceded by the making of models in wax or plaster. In the 19th century it was common to work from plaster to stone by means of a mechanical device known as a pointing machine. Much of the manual work could be done by studio assistants and it was possible to make enlargements from a smaller model. When this is bypassed, as was prevalent in the 20th century, it is normal to talk of “direct carving”. Because of the unpredictability of wood it was only practical to use the pointing machine for stone carving.

B.

Modelling

Modelling consists of addition to, or building up of, form. The materials used are soft and yielding and can be easily shaped, enabling rapid execution. Thus, a sculptor can capture and record fleeting impressions in much the same way a painter does in a quick sketch. Clay or claylike substances (such as terracotta) have been used for modelling since ancient times. This must be baked or it will be too fragile to survive. Wax, which can be coloured, is another modelling material. Plaster, which can be hard or soft, can be worked by a combination of modelling and carving. Except in the case of very small pieces, a metal or wooden structure known as an armature is used for support.

C.

Casting

With careful handling and storage, as in a museum, plaster and terracotta can survive indefinitely but the rigours of its public role demand that modelled sculpture usually be cast in metal. Two methods of casting are used: the cire perdue, or lost-wax process, and sand-casting. Both methods have been used since antiquity, although the lost-wax process is more widely employed. Sand casting is an intricate process in which fine, cohesive sand, mixed with a small amount of clay, is used to produce a positive model and slightly larger negative mould of the artist's original, between which molten metal is poured and allowed to harden. Since the 1920s it has been normal to control the issue of bronze casts by means of limited editions to preserve quality, maintain rarity value, and protect artist and collector alike from unauthorized copies. Bronze casting has been used to give permanence to other fragile, three-dimensional works such as wood constructions or even carvings.

D.

Construction and Assemblage

Although traditional techniques are still employed, much 20th-century sculpture is created by construction and assemblage (see Cubism and Constructivism below). It is essentially an additive process that has its origins in collage.

E.

Free Standing and Relief

The fully free-standing sculpture usually stands on a plinth or base. It can often be viewed from different angles and it is even argued that this gives it a superiority over painting. The most common form is the single figure and the more figures that are introduced the more sculpture tends to be viewed like a painting, that is to say from a single angle. Therefore, in the case of more complex scenes, which involve a number of figures or in which figures need to be related to a background, it is usual to employ relief. This is designed to be viewed like a painting from a single angle and can employ painterly devices to give the illusion of depth. In some sculptural monuments a free-standing figure is placed on a base, which itself contains reliefs that comment on the person commemorated.

F.

Colour

Sculpture is above all the art of three-dimensional form, but colour can play a role. Sculpture can be painted, as was done by the ancient Greeks. Different colours of wax can be used. Baroque sculptors such as Gianlorenzo Bernini employed coloured marble to vivid effect. Twentieth-century sculptors such as Henry Moore and Barbara Hepworth have tended to prefer stones with varied colours and textures to pure white marble. Bronze casts if unprotected will discolour anyway, so the process is stabilized by finishing them in different colours by a chemical procedure known as patination. Up to the late 19th century, dark browns and near blacks were favoured, but some 20th-century sculptors such as Constantin Brancusi preferred the golden sheen of natural bronze, suggesting a machine-like precision. Also popular in the 20th century has been an emerald green, a rather lurid and stylized version of the effect achieved by burying bronze in the soil for centuries. The spectator today tends to associate the sculptures of Auguste Rodin in terms of dark brown bronze casts. His contemporaries would think of them primarily as white, either as plasters or marble carvings.