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'Scagliola' (from the Italian ''scaglia'', meaning "chips") is a technique for producing stucco columns, sculptures, and other architectural elements that resemble marble. A comparable material is terrazzo. "Marmorino" is a synonym, but scagliola and terrazzo should not be confused with plaster of Paris, which is one ingredient.

Contents

Method

In history

See also

Notes

Method

Batches of pigmented plaster (ground alabaster or gypsum) modified with animal glue are applied to molds, armatures and pre-plastered wall planes in a manner that accurately mimics natural stone, breccia and marble. In one technique, veining is created by drawing strands of raw silk saturated in pigment through the plastic mix. Another technique involves trowelling on several layers of translucent renders and randomly cutting back to a previous layer to achieve colour differential similar to hewn marble. When dry, the plaster is polished until it resembles stone. The damp surface was pumiced smooth, then buffied with a linen cloth impregnated with Tripoli, a siliceous rottenstone, and charcoal; finally it was buffed with oiled felt; beeswax was sometimes used for this purpose. Because the colours are integral to the plaster, the pattern is more resistant to scratching than with other techniques, such as painting on wood.

There are two scagliola techniques: in traditional ''Bavarian'' scagliola coloured batches of plaster of Paris are worked to a stiff, dough-like consistency. The plaster is modified with the addition of animal glues such as isinglass or hide glue. ''Marezzo scagliola'' or ''American scagliola'' is worked with the pigmented batches of plaster in a liquid state and relies mainly on the use of ''Keene's cement'', a unique gypsum plaster product in which plaster of Paris was steeped in alum or borate, then burned in a kiln and ground ton a fine powder; invented around 1840, it sets to an exceptionally hard state.^[1] It is typically used without the addition of animal glues. ''Marezzo scagliola'' is often called ''American scagliola'' because of its widespread use in the United States in the late nineteenth and early twentieth century. Slabs of ''Marezzo scagliola'' may be used as table tops. When set, scagliola is hard enough to be turned on a lathe to form vases, balusters and finials.

In history

While there is evidence of scagliola decoration in ancient Roman architecture, scagliola decoration became popular in Italian Baroque buildings in the 17th century, and was imitated throughout Europe until the 19th century. An early use of scagliola in England is in a fireplace at Ham House, Surrey. Italian plasterworkers produced scagliola columns and pilasters for Robert Adam at Syon House (notably the columns in the Anteroom]]) and at Kedleston (notably the pilasters in the Saloon). In 1816 the Coade Ornamental Stone Manufactory extended their practice to include scagliola; their scagliola was used by Benjamin Dean Wyatt at Apsley house, London. ^[2]
In the United States it was popular in the 19th and 20th centuries. Important US buildings featuring scagliola include Allen County Courthouse in Fort Wayne, Indiana, Belcourt Castle in Newport, Rhode Island, and in the Kansas State Capitol in Topeka, Kansas. St. Louis Union Station in St. Louis, MO prominently features scagliola in its magnificent Grand Hall.
Scagliola has historically been considered an ersatz material and an inexpensive alternative to natural stone. However, it has eventually come to be recognised as an exceptional example of the plasterer's craft and is now prized for its historic value as well as being used in new construction because of its benefits as a plastic material suited to molding in ornate shapes.
Scagliola columns are not generally built of the solid material. Instead scgliola is trowelled onto a canvas which is wrapped around the column's core, and the canvas peeled away when semi-hardened. The scagliola is then surfaced in place.^[3]

See also

★ Sgraffito

★ Stucco

★ Terrazzo

★ Venetian plaster

★ Coade stone

Notes

1. Theodore H. M. Prudon, "Simulating Stone, 1860-1940: Artificial Marble, Artificial Stone, and Cast Stone" '' Association for Preservation Technology International Bulletin'' '21'.3/4 (1989), pp. 79-91.
2. John E. Ruch, "Regency Coade: A Study of the Coade Record Books, 1813-21" ''Architectural History'' '11' (1968, pp. 34-56,106-107) pp 35, 39.
3. Alfred M. Staehli, "Scagliola: Restoration of an Antique Plaster Finish in the Portland City Hall, Oregon" ''Bulletin of the Association for Preservation Technology'' '16'.2 (1984), pp. 44-50.