The Conservation of Plaster Casts in the Nineteenth Century

Plaster casts of ancient sculpture were widely collected by universities and museums through the nineteenth century. One of the intended functions of these casts was to preserve accurate 3D records of the sculptures, many of which were in remote locations around the world, often vulnerable to damage from weathering and vandalism. Gypsum plaster makes excellent casts, capturing fine surface details; however, it is also soft, porous, and easily damaged. This paper draws upon historical archives and patents to reveal the considerable efforts made during this period to create new techniques, recipes, and equipment to try to protect the casts. Case studies are selected primarily from the collection of casts put together by Walter Copland Perry in the 1880s, originally for the South Kensington Museum but transferred in 1907 to the British Museum. Samples were taken from a number of these casts and examined using scanning electron microscopy with energy dispersive spectroscopy. These results, combined with archival evidence, demonstrate that protective coatings were carefully applied in thin coatings to many of the casts. Barium appears to have played an important part in these protective treatments and further testing is recommended to evaluate the precise nature of its role. These treatments successfully protected the delicate surfaces of the casts for many years. However, later neglect means that these casts now suffer from a range of other threats to their condition.