Scagliola (from the Italian scaglia, meaning "chips"), is a technique for producing stucco columns, sculptures, and other architectural elements that resemble marble. The Scagliola technique came into fashion in 17th century Tuscany as an effective substitute for costly marble inlays, the pietra dura works created for the Medici family in Florence.
Scagliola is a composite substance made from selenite, glue and natural pigments, imitating marble and other hard stones. The material may be veined with colors and applied to a core, or desired pattern may be carved into a previously prepared scagliola matrix. The pattern’s indentations are then filled with the colored, plaster-like scagliola composite, and then polished with flax oil for brightness, and wax for protection. The combination of materials and technique provides a complex texture, and richness of color not available in natural veined marbles.
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 jasper. When dry, the damp surface was pumiced smooth, then buffed 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 to a fine powder; invented around 1840, it sets to an exceptionally hard state. 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.
The correspondence between British Resident in Florence Sir Horace Mann and Horace Walpole describes the process of obtaining a prized scagliola table top. Having received his first top from the Irishman Friar Ferdinando Henrico Hugford (1695–1771) around 1740 Walpole had asked his friend Mann to acquire some more... (one of these tables is at The Vyne. That table has the arms of Walpole (with his post 1726 Garter Knight embelishments) impaling Shorter - for Prime Minister Sir Robert Walpole and his first wife Catherine Shorter, who died 20 August 1737. He married Maria Skerret in early 1738, thus The Vyne's table could seem have been ordered before c1736-37).
In a letter dated 26 November 1741 Mann writes to Walpole:
In modern times - Tusmore House Oxfordshire
The great triumph of the saloon, however, is the use of scagliola, including the richly coloured and figured Sienna shafts of the eight fluted Corinthian columns...and the urns, entablature and balustrade to the second-floor landing which gives access to four plaster-vaulted ante rooms serving the main bedrooms. All this scagliola was produced by Richard Feroze, England's leading contemporary scagliola-maker.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.
In the United States scagliola 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, in the Kansas State Capitol in Topeka, Kansas, and in Shea's Performing Arts Center in Buffalo, New York. St. Louis Union Station in St. Louis, Missouri, prominently features scagliola in its magnificent Grand Hall, the Rialto Square Theatre, Joliet, IL, Cathedral of St. Helena in Helena, MT, Milwaukee Public Library Central Library in Milwaukee, WI and the French Lick Resort Casino, French Lick, IN which recently underwent a major restoration.
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.