house construction technique involving the application of plaster to walls and ceilings, exterior plasterwork being of a different composition and generally known as stucco. Plaster was used by the Egyptians (chiefly as a surface to receive color decorations) and by the Greeks. The Romans used it extensively, and there remain, especially at Pompeii, many ceilings and walls, with beautiful relief ornamentation, of a hard, fine plaster. Italian Renaissance artists imitated this Roman work, and relief ornament in plaster was employed in England for the rich ceilings and interiors of the reigns of Henry VIII, Elizabeth I, and James I and later in those designed by the architects Robert and James Adam. In the United States many fine ornamented plaster ceilings were executed in the 18th cent. Interior plastering is applied over a base that will furnish a proper grip—by means of interstices provided by wood lath or metal lath or by irregularities of surface such as in hollow tile. To secure best results three successive coats of plaster are requisite in most types of work. The first, or scratch, coat, composed of sand and lime mixed with abundant hair or fiber, must be thoroughly grounded into the lath and before it hardens is scratched to provide key, or adhesion, for the next coat. The second, called the brown coat in the United States and the floating coat in Great Britain, is composed of sand and lime, without hair, and is worked to a hard, compact texture, with its surface roughened to receive the final coat. The third, or white, finishing coat is composed of plaster of paris, slaked lime, and white sand, mixed with water to form a paste. It is troweled on the wall to form a hard, smooth surface, the process requiring a skilled worker. Moldings, cornices, and relief ornament are cast separately and then mounted into place. In former times ornamental details were molded in their location, from the damp plaster. Often substituted for plastered walls is plasterboard, a prefabricated material composed of paperboard and gypsum.
Summary Article: plastering
From The Columbia Encyclopedia