A plastercast is a copy made in plaster of another 3-dimensional form. The original from which the cast is taken may be a sculpture, building, a face, a pregnant belly, a fossil or other remains such as fresh or fossilised footprints - particularly in palaeontology. Sometimes a blank block of plaster itself was carved to produce mock-ups or first drafts of sculptures that would ultimately be sculpted in stone, by measuring exactly from the cast, for example by using a pointing machine. These are still described as plaster casts. Examples of these by John Flaxman may be found in the central rotunda of the library at University College London, and elsewhere in the University's collections. It may also describe a finished original sculpture made out of plaster, though these are rarer.
Method
is applied to the original to create a mould or cast of the original. This mould is then removed and fresh plaster is poured into it, creating a copy in plaster of the original. Usually very elaborate moulds were made out of several to even dozens of pieces, to cast the more difficult undercut sculptures. Plaster is not flexible, therefore the moulds were made as 3D jigsaw puzzles for easy removal of the original and the cast from the mould. Later gelatine, rubber and silicone moulds were used, backed by plaster or polyester for support.
History
Early
The practice of reproducing famous sculptures in plaster originally dates back to the sixteenth century when Leone Leoni assembled a collection of casts in Milan. He collected "as many of the most celebrated works… carved and cast, antique and modern as he was able to obtain anywhere". Such private collections, however, remained modest and uncommon until the 18th century.
Classical sculpture
Use of such casts was particularly prevalent among classicists of the 18th and 19th centuries, and by 1800 there were extensive collections in Berlin, Paris, Vienna and elsewhere. By creating copies of ancient Greek and Roman sculptures held at various museums across Europe in this way, a reference collection of all the best and most representative sculptural types could be formed, at a fraction of the cost of purchasing original sculptures, which scholars could consult without necessarily having to travel abroad to see all the originals. These casts could also be used in experiments in polychromy, reconstruction, and for filling holes in a museum's collections of actual sculpture. Formula plaster of Paris- CASO4.1/2H2O
Other ancient cultures
The technique was also applied later that century to reliefs from Ancient Egypt and friezes from Mesopotamia, as well as to medieval and Renaissance sculptures. In the early 19th century, for example, perhaps as an expression of national pride, casts were made of outstanding national monuments particularly in France and Germany.
