The Ornamental Plaster Trade
As builders and architects were hired by an increasingly affluent clientele, ornamental plaster shops developed from the single artisan operations of the 18th century into the complex establishments of the early 20th century. American plaster studios employed immigrant and, later, native craftsmen.
Plasterers' guilds were in existence in Philadelphia in the 1790s. In 1864, a plasterers' union was organized in the United States with members from the British Isles whose work there had been limited to palaces and churches. English and European craftsmen came to America where the demand for their skills had increased by the decade, offering them the unparalleled opportunity to open their own shops. Over the years, plaster elements became so popular in decorating interior spaces that a major industry was established. By the 1880s, catalogs were available from which property owners could select ornamentation for their splendid new buildings.
Methods of Production. Historically, ornamental plasterwork has been produced in two ways: it would be run in place (or on a bench) at the site; or cast in molds in a workshop. Plain plaster molding without surface ornamentation was usually created directly on the wall, or run on a flat surface such as a plasterer's workbench and attached to the wall after it set. Ornament such as coffering for ceilings, centers for light fixtures (medallions), brackets, dentils, or columns were cast in hide glue (gelatin) or plaster molds in an offsite shop, often in more than one piece, then assembled and installed in the building.
Decorative Plaster Forms
Cornices, Medallions, Coffers. Three decorative plaster forms in particular--the cornice, the ceiling medallion, and the coffered ceiling--historically comprised much of the ornamental plasterers' business. These forms appear individually or in combination from the 18th to 20th century, irrespective of stylistic changes.
For example, an elaborate parlor cornice consisted of plain moldings made of gypsum and lime run atop temporary lattice strips around the room. Tooling for plain-run moldings called for a sheet metal template of the molding profile mounted on a wooden "horse" . Mitering was accomplished using a plaster and lime putty gauge (mix) tooled with miter rods at the joints. Decorative "enrichments" such as leaves, egg and dart moldings, and bead and reel units were cast in the shop and applied to the plain runs using plaster as an adhesive. Painting, glazing, and even gilding followed. Large houses often had plain run cornices on the upper floors which were not used for entertaining; modest houses also boasted cornice work without cast enrichment.
Among the most dramatic of ornamental plaster forms is the parlor ceiling medallion. Vernacular houses often used plain-run concentric circles from which lighting fixtures descended, usually hung from a wrought iron hook embedded in the central ceiling joist. More elaborate medallions were composed of shop-cast pieces, such as acanthus foliage often alternating with anthemia or other decorative designs. Medallions usually related stylistically to the cornice ornament found in the room and could be created with or without a plain-run surround.
Of particular importance to the art of ornamental plaster was the mid-19th century double parlor plan. Architects often specified matching medallions of robust proportions and ornamentation. Later, in 20th century American Colonial Revival architecture, architects called for Federal style ceiling medallions. Some of the more successful were graceful one-piece units, utilizing classical motifs such as garlands and swags, and in their simplicity, reminiscent of Adamesque designs of the 1760s.
Yet another significant decorative form is the coffered ceiling. Coffering units were cast in the shop or onsite, then installed with hanging wires to form the ceiling.
Ceiling design varied from period to period as to depth, panel shape, and ornamental complexity. Not always flat, coffering is seen inside domes, within barrel vaults and groin ceilings, along overhead ribs and soffits. Rosettes are usually centered in the panels and often enrich the intersections of elaborate stiles bordering the panels. Flat ceiling coffers are generally identical in reflected plan; on domed or barrel ceilings, coffers differ from course to course so as to appear identical from various sight lines. The finish treatment of a coffered ceiling frequently exhibits the height of the painter's craft.
Foremost examples of ceiling coffering include the United States Capitol, and Washington D. C.'s Union Station. As a popular decorative form with inherent acoustical benefits, the coffered ceiling is seen across the United States in many large public spaces such as theaters, courthouses, railroad stations, and hotels.
Unfortunately, these supposedly enduring decorative forms created by ornamental plaster tradesmen are subjected to the ravages of both nature and man and, consequently, seldom remain as originally designed. Minor changes of taste are perhaps the least injurious to plasterwork. Considerably greater damage and deterioration are caused by radical changes in building use and poor maintenance practices. Fortunately, in most cases, the form, detailing, and finish of historic ornamental plaster can be recaptured through careful repair and restoration.