Carving Takes Away, Casting Adds

There are two ways to make a sculpture, and the difference between them decides almost everything else: what poses are possible, how the work is planned, whether mistakes can be recovered, and what the word 'original' means.

Carving takes material away. Every cut is permanent, the sculptor works from the outside in, and a serious error ends the block. Michelangelo abandoned works when the marble revealed a flaw; the unfinished Slaves in Florence have figures emerging from stone that was never cut back.

Modelling adds material. Clay or wax is built up, changed, pulled off and rebuilt, and then the result is preserved by casting it in bronze. The sculptor can work all day and reverse it all the next morning.

The material consequence comes first. Marble has almost no tensile strength, so an unsupported projecting limb snaps under its own weight. Hence the tree stumps, drapery falling conveniently against a leg, and struts between hand and hip that populate classical sculpture. Many Roman marbles are copies of Greek bronzes, and the supports are engineering added in translation: the bronze original needed none, because metal can hold a limb in the air.

Bronze is cast by the lost-wax method, which is four thousand years old and essentially unchanged. A wax model (solid for small pieces, a wax skin over a clay core for large ones) is encased in an investment mould. The whole thing is heated until the wax runs out, leaving a cavity of exactly the wax's shape. Molten bronze goes in. When it cools the mould is broken away.

The metal records everything the wax held: tool marks, thumbprints, the drag of a fingernail. A bronze carries the evidence of the sculptor's hand even when the pour was done by a foundry the sculptor never visited, because the hand is in the model.

Which is where authenticity gets complicated.

The mould can be used again. From one model a foundry can produce many casts, and casting has always been a delegated industrial process. So the convention in sculpture is the edition: a fixed number of casts, each counted as an original. French law recognises up to twelve casts of a Rodin model as originals, and permits posthumous casting under the authority of the estate.

That means the Rodin in front of you may have been poured in 1975 from a model made in 1890 by a man who died in 1917, and it is an original, not a reproduction. Authenticity here rests on the authority of an estate, a foundry and a number stamped in the metal. No painter could use that definition. It is why sculpture markets argue about foundry marks and edition numbers where painting markets argue about brushwork.

There is a related correction to make about the marbles themselves.

They were painted. Pigment traces survive on Greek and Roman sculpture and can be mapped with raking light, ultraviolet imaging and chemical analysis, and the reconstructions are startling: patterned textiles, coloured eyes, skin tones, weapons picked out. The white classicism on which European taste was founded is weathering.

Winckelmann, who more or less invented art history in the 1760s, built an aesthetic of noble simplicity and calm grandeur on objects whose surfaces had been washed away, and when traces of colour turned up they were sometimes scrubbed off by curators who knew what classical sculpture ought to look like. Reconstructions with the colour restored strike most modern viewers as garish, which is a fact about our eyes rather than about Greek taste.

Two conclusions worth carrying out of the room. What survives is not what was made; and the definition of an original object depends on how the object was produced, which is why a cast made sixty years after a death can be authentic while a perfect copy of a painting never is.