What Is Sculpture? Carving, Modelling, Casting and Assembling in Three Dimensions

Carving is subtraction: the sculptor starts with a block of stone, wood or ivory and removes everything that is not the figure. It is the oldest method and the least forgiving, since a piece cut away cannot be put back, and it favours compact, solid forms, because a thin projecting arm or a raised leg will snap under its own weight or the chisel. The Egyptians carved figures with arms held to their sides and a block of stone left behind the legs for that reason; the Greeks learned to free the figure by supporting it with a tree stump or a fall of drapery, and Michelangelo, who said he simply released the figure already inside the marble, worked from the front of the block inward as though the statue were rising out of a bath. Marble is soft enough to cut and fine enough to polish to skin; granite is hard and gives the severe forms of Egypt; wood is light and carves in any direction, and rots.

Modelling is addition: building a form up in a soft material, clay, wax or plaster, that can be pushed, pulled and revised. It is the freest of the methods and the one in which sculptors think, since a clay sketch can be made in an hour and changed until it is right. Its limitation is that clay is fragile and wax melts, so a modelled work is usually a stage on the way to something else, fired as terracotta, which the Chinese did for an army of seven thousand soldiers in the third century BC, or cast in a permanent material. Rodin modelled everything in clay and had assistants do the rest; his Burghers of Calais and Thinker exist as bronzes because of the next method.

Casting turns a modelled original into a durable copy by pouring a liquid that sets, and the liquid is usually bronze. The lost-wax process, used since the Bronze Age, works like this:

• •A model is made in clay and a mould taken from it
• •The mould is lined with a layer of wax, which becomes a hollow wax copy of the model
• •The wax copy is packed inside and out with a heat-proof material and heated until the wax runs out, leaving a cavity
• •Molten bronze is poured into the cavity and cooled
• •The investment is broken away, the channels that fed the metal are cut off, and the surface is finished and coloured with chemicals to give the patina

The fourth method is the youngest. In 1912 Picasso made a guitar out of cut and folded cardboard, and in 1913 Marcel Duchamp fixed a bicycle wheel to a stool, and sculpture as the joining of found or fabricated parts was born. Welded steel followed, with Julio Gonzalez teaching Picasso to weld in the 1920s and David Smith and Anthony Caro building open, linear works in the 1950s and 1960s that had no core and no front; Alexander Calder hung shapes from wires and let the air move them, and called them mobiles. Assembling freed sculpture from the mass that carving and casting required. A work could now be a line in space, a room, a pile of bricks, a shark, a light, or an arrangement that exists only as instructions, and much of what is made under the name today is of this kind.

For most of its history sculpture was the art of the human body, because the body was what gods, rulers and the dead were shown as, and the great sculptural traditions, Egyptian, Greek, Indian, Chinese, African, Gothic, Renaissance, are mostly traditions of the figure. The Greeks worked out how a standing body carries its weight, with one leg bearing and the hip swung, and that pose, the contrapposto, runs from the Kritios Boy of 480 BC through Donatello and Michelangelo to the fashion photograph. Relief, in which the figure is only partly freed from a background, carried narrative, on temple friezes and cathedral doors. The break came in the twentieth century, when Brancusi polished a bird into a single curve, Henry Moore opened holes through the figure, and the assemblers abandoned it. Since then sculpture has been the name for any made thing that asks to be walked around, and the walk is still the test.

Sculpture is art in three dimensions, made by carving material away from a block, modelling it up in clay or wax, casting a model in bronze or another liquid that sets, or assembling found and fabricated parts, a method invented in 1912 that freed the form from solid mass. For most of history its subject was the human figure, from Egyptian and Greek statues to Rodin; since Brancusi, Moore and the assemblers it has been anything that occupies space and is meant to be walked around.