Bronze casting (lost-wax) is an ancient sculptural technique in which a wax model is encased in clay, melted out, and replaced by molten bronze.
The lost-wax process (Italian: 'cire perdue') is the principal technique by which most bronze sculpture has been produced for over five thousand years. The artist first models the work in wax over a clay or ceramic core; the wax is then encased in a thick clay mould, with channels cut into it. When the mould is heated, the wax melts and runs out, leaving a hollow cavity into which molten bronze can be poured. After cooling, the outer mould is broken away to reveal the bronze cast, which is then chased, polished, and patinated. The earliest surviving lost-wax bronzes are from the Indus Valley civilisation around 3500 BCE. Greek classical bronzes — Polykleitos's Doryphoros, the Riace bronzes, the Charioteer of Delphi — set the Western standard. Donatello's bronze David (c. 1440) was the first major free-standing bronze nude since antiquity. The Renaissance technique handed down through Cellini's treatise on goldsmithing and sculpture is essentially the same one used by Henry Moore, Louise Bourgeois, and contemporary foundries today.