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Plasterwork refers to construction or ornamentation done with plaster, such as a layer of plaster on an interior or exterior wall structure, or plaster decorative moldings on ceilings or walls. This is also sometimes called pargeting. The process of creating plasterwork, called plastering or rendering, has been used in building construction for centuries. ==History== The earliest plasters known to us were lime-based. Around 7500 BC, the people of 'Ain Ghazal in Jordan used lime mixed with unheated crushed limestone to make plaster which was used on a large scale for covering walls, floors, and hearths in their houses. Often, walls and floors were decorated with red, finger-painted patterns and designs. In ancient India and China, renders in clay and gypsum plasters were used to produce a smooth surface over rough stone or mud brick walls, while in early Egyptian tombs, walls were coated with lime and gypsum plaster and the finished surface was often painted or decorated. Modelled stucco was employed throughout the Roman Empire. The Romans used mixtures of lime and sand to build up preparatory layers over which finer applications of gypsum, lime, sand and marble dust were made; pozzolanic materials were sometimes added to produce a more rapid set. Following the fall of the Roman Empire, the addition of marble dust to plaster to allow the production of fine detail and a hard, smooth finish in hand-modelled and moulded decoration was not used until the Renaissance. Around the 4th century BC, the Romans discovered the principles of the hydraulic set of lime, which by the addition of highly reactive forms of silica and alumina, such as volcanic earths, could solidify rapidly even under water. There was little use of hydraulic mortar after the Roman period until the 18th century. Plaster decoration was widely used in Europe in the Middle Ages where, from the mid-13th century, gypsum plaster was used for internal and external plaster. Hair was employed as reinforcement, with additives to assist set or plasticity including malt, urine, beer, milk and eggs. In the 14th century, decorative plasterwork called pargeting was being used in South-East England to decorate the exterior of timber-framed buildings. This is a form of incised, moulded or modelled ornament, executed in lime putty or mixtures of lime and gypsum plaster. During this same period, terracotta was reintroduced into Europe and was widely used for the production of ornament. In the mid-15th century, Venetian skilled workers developed a new type of external facing, called marmorino made by applying lime directly onto masonry. In the 16th century, a new highly decorative type of decorative internal plasterwork, called scagliola, was invented by stuccoists working in Bavaria. This was composed of gypsum plaster, animal glue and pigments, used to imitate coloured marbles and pietre dure ornament. Sand or marble dust, and lime, were sometimes added. In this same century, the sgraffito technique, also known as graffito or scratchwork was introduced into Germany by Italian artists, combining it with modelled stucco decoration. This technique was practised in antiquity and was described by Vasari as being a quick and durable method for decorating building facades. Here, layers of contrasting lime plaster were applied and a design scratched through the upper layer to reveal the colour beneath. The 17th century saw the introduction of different types of internal plasterwork. Stucco marble was an artificial marble made using gypsum (sometimes with lime), pigments, water and glue. Stucco lustro was another a form of imitation marble (sometimes called stucco lucido) where a thin layer of lime or gypsum plaster was applied over a scored support of lime, with pigments scattered on surface of the wet plaster. The 18th century gave rise to renewed interest in innovative external plasters. Oil mastics introduced in the UK in this period included a "Composition or stone paste" patented in 1765 by David Wark. This was a lime-based mix and included "oyls of tar, turpentine and linseed" besides many other ingredients. Another "Composition or cement", including drying oil, was patented in 1773 by Rev. John Liardet. A similar product was patented in 1777 by John Johnson. Widely used by the architect Robert Adam who in turn commissioned George Jackson to produce reverse-cut boxwood moulds (many of which to Adam designs). Jackson formed an independent company which still today produces composition pressings and retains a very large boxwood mould collection. In 1774, in France, a mémoire was published on the composition of ancient mortars. This was translated into English as "A Practical Essay on a Cement, and Artificial Stone, justly supposed to be that of the Greeks and Romans" and was published in the same year. Following this, and as a backlash to the disappointment felt due to the repeated failure of oil mastics, in the second half of the 18th century water-based renders gained popularity once more. * Mixes for renders were patented, including a "Water Cement, or Stucco" consisting of lime, sand, bone ash and lime-water (Dr Bryan Higgins, 1779). * Various experiments mixing different limes with volcanic earths took place in the 18th century. John Smeaton (from 1756) experimented with hydraulic limes and concluded that the best limes were those fired from limestones containing a considerable quantity of clayey material. * In 1796, Revd James Parker patented Parker's "Roman Cement". This was a hydraulic cement which, when mixed with sand, could be used for stucco. It could also be cast to form mouldings and other ornaments. It was however of an unattractive brown colour, which needed to be disguised by surface finishes. Natural cements were frequently used in stucco mixes during the 1820s. The popularisation of Portland cement changed the composition of stucco, as well as mortar, to a harder material. The development of artificial cements had started early in the 19th century. In 1811, James Frost took out a patent for an artificial cement obtained by lightly calcining ground chalk and clay together. The French Engineer Louis Vicat in 1812–1813 experimented with calcining synthetic mixtures of limestone and clay, a product he introduced in 1818. In 1822, in the UK, James Frost patented (another?) process, similar to Vicat's, producing what he called "British cement". Portland cement, patented in 1824 by Joseph Aspdin, was called so because it was supposed to resemble Portland stone. Aspdinís son William, and later Isaac Johnson, improved the production process. A product, very similar to modern Portland cement, was available from about 1845, with other improvements taking place in the following years. Thus, after about 1860, most stucco was composed primarily of Portland cement, mixed with some lime. This made it even more versatile and durable. No longer used just as a coating for a substantial material like masonry or log, stucco could now be applied over wood or metal lath attached to a light wood frame. With this increased strength, it ceased to be just a veneer and became a more integral part of the building structure. Early 19th century rendered façades were colour-washed with distemper; oil paint for external walls was introduced around 1840. The 19th century also saw the revival of the use of oil mastics. In the UK, patents were obtained for "compositions" in 1803 (Thomas Fulchner), 1815 (Christopher Dihl) and 1817 (Peter Hamelin). These oil mastics, as the ones before them, also proved to be short-lived. Moulded or cast masonry substitutes, such as cast stone and poured concrete, became popular in place of quarried stone during the 19th century. However, this was not the first time "artificial stone" had been widely used. Coade Stone, a brand name for a cast stone made from fired clay, had been developed and manufactured in England from 1769 to 1843 and was used for decorative architectural elements. Following the closure of the factory in South London, Coade stone stopped being produced, and the formula was lost. By the mid 19th century manufacturing centres were preparing cast stones based on cement for use in buildings. These were made primarily with a cement mix often incorporating fine and coarse aggregates for texture, pigments or dyes to imitate colouring and veining of natural stones, as well as other additives. Also in the 19th century, various mixtures of modified gypsum plasters, such as Keene's cement, appeared. These materials were developed for use as internal wall plasters, increasing the usefulness of simple plaster of Paris as they set more slowly and were thus easier to use. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「plasterwork」の詳細全文を読む スポンサード リンク
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