Sculpture, especially that which stands outdoors, is particularly vulnerable to environmental changes. Placing the sculpture in a temperature- and humidity-controlled situation is the best means by which to preserve it. Stone sculpture requires periodic washing; either steam, spray, or trickled water is used, depending on the porosity of the stone. Soap, but not detergent, may also be applied. Broken sculptures may be mended with clear, cold-setting adhesives, sometimes mixed with a suitably colored filler, or by means of dowelling. Large pieces of sculpture are held together with metal dowels, usually of copper, stainless steel, or brass.
Broken wood sculpture is also dowelled, as is ivory, and special cements may also be used to fill cracks. Wood sculpture is also vulnerable to woodworm and dry rot and may be treated with insecticide and fungicide. Badly decayed wood works may sometimes be preserved by means of impregnation with a plastic medium.
Metal sculpture may be waxed to protect it from atmospheric corrosives. Bronze acquires a patina, or irregular surface pattern caused by deposits of sulfides and oxides, that is widely considered aesthetically pleasing, whereas patina on lead objects results in eventual decay. Cracks in metal sculpture may be filled with special adhesives. Corrosion may be halted by electrolytic reduction, which, however, destroys patina. Various chemical solvents and mechanical techniques are used to remove specific incrustations.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.