Plaster: Facts, Discussion Forum, and Encyclopedia Article

All Topics

Plaster

Plaster

	Email		Print
	Bookmark		Link

	Plaster
	Home
	The term plaster can refer to plaster of Paris, lime plaster Lime plaster Lime plaster is a mixture of calcium hydroxide and sand . Carbon dioxide in the atmosphere causes the plaster to set by transforming the calcium hydroxide into calcium carbonate .... , or cement plaster. This article deals mainly with plaster of Paris. Plaster of Paris is a type of building material based on calcium sulfate Calcium sulfate Calcium sulfate is a common laboratory and industrial chemical. In the form of ?-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu.... hemihydrate Hydrate Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood.... , nominally CaSO₄·0.5H₂O. It is created by heating gypsum Gypsum Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula calciumsulfuroxygen4?2water.... to about 150 °C. 2 CaSO₄·2H₂O ? 2 CaSO₄·0.5H₂O + 3 H₂O (released as steam). A large gypsum deposit at Montmartre Montmartre Montmartre is a hill which is 130 metres high, giving its name to the surrounding district, in the north of Paris in the 18eme arrondissement, Paris, a part of the Rive Droite.... in Paris Paris Paris is the Capital of France and the country's largest city. It is situated on the river Seine, in northern France, at the heart of the ?le-de-France Regions of France .... is the source of the name. When the dry plaster powder is mixed with water, it re-forms into gypsum. Plaster is used as a building material similar to mortar Mortar (masonry) Mortar is a workable paste formed by mixture of cement, water and fine aggregate masonry to bind construction blocks together and fill the gaps between them.... or cement Cement In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together.... . Like those materials plaster starts as a dry powder that is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar Mortar (masonry) Mortar is a workable paste formed by mixture of cement, water and fine aggregate masonry to bind construction blocks together and fill the gaps between them.... and cement Cement In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together.... , plaster remains quite soft after drying, and can be easily manipulated with metal tools or even sandpaper Sandpaper Sandpaper is a form of paper where an abrasive material has been fixed to its surface.Sandpaper is part of the "coated abrasives" family of abrasive products.... . These characteristics make plaster suitable for a finishing, rather than a load-bearing material. Plaster was a common building material for wall surfaces in a process known as lath and plaster Lath and plaster Lath and plaster is a building process used mainly for interior walls in Canada and the United States until the late 1950s. After the 1950s, drywall began to replace the lath and plaster process in the these countries.... , whereby a series of wooden strips on a studwork Wall stud A wall stud is a vertical member in the light frame construction techniques called Balloon framing and framing #Platform_framing of a building's wall .... frame was covered with a semi-dry plaster that hardened into a surface. The plaster used in most lath and plaster construction was mainly lime plaster Lime plaster Lime plaster is a mixture of calcium hydroxide and sand . Carbon dioxide in the atmosphere causes the plaster to set by transforming the calcium hydroxide into calcium carbonate .... , with a cure time of about a month. To stabilize the lime plaster during curing, small amounts of Plaster of Paris were incorporated into the mix. Because Plaster of Paris sets quickly, "retardants" were used to slow setting time enough to allow workers to mix large working quantities of lime putty plaster. A modern form of this method uses expanded metal mesh over wood or metal structures, which allows a great freedom of design as it is adaptable to both simple and compound curves. Today this building method has been partly replaced with drywall Drywall Drywall is a common building material typically made of a layer of gypsum plaster pressed between two thick sheets of paper, then kiln dried. Drywall is used globally for the finish construction of interior walls and ceilings.... , also composed mostly of gypsum plaster. In both these methods a primary advantage of the material is that it is resistant to a fire within a room and so can assist in reducing or eliminating structural damage or destruction provided the fire is promptly extinguished. One of the skills used in movie and theatrical sets is that of "plasterer", and the material is often used to simulate the appearance of surfaces of wood, stone, or metal. Nowadays, plasterers are just as likely to use expanded polystyrene, although the job title remains unchanged. Use in architecture Plaster may also be used to create complex detailing for use in room interiors. These may be geometric (simulating wood or stone) or naturalistic (simulating leaves, vines, and flowers) These are also often used to simulate wood or stone detailing found in more substantial buildings. Use in the arts Many of the greatest paintings in Europe, like Michelangelo's Sistine Chapel ceiling Sistine Chapel ceiling The Sistine Chapel ceiling, painted by Michelangelo between 1508 and 1512, is one of the most renowned artworks of the Renaissance painting. The ceiling is that of the large Sistine Chapel built within the Vatican City by Pope Sixtus IV, begun in 1477 and finished by 1480.... are executed in Fresco Fresco Fresco is any of several related painting types, done on plaster on walls or ceilings. The word fresco comes from the Italian word affresco which derives from the adjective fresco , which has Latin origins.... , meaning they are painted on a thin layer of wet plaster, called intonaco Intonaco Intonaco is an Italian term for the final, very thin layer of plaster on which a fresco wall painting is painted. The painting is done whilst the plaster is still wet, in order to allow the pigment to penetrate into the intonaco itself.... (in fact the general term for plaster in Italian); the pigments sink into this layer so that the plaster itself becomes the medium holding them, which accounts for the excellent durability of fresco. Additional work may be added a secco on top of the dry plaster, though this is generally less durable. Plaster may be cast directly into a damp clay mold. In creating this moldmolds (molds designed for making multiple copies) or waste molds (for single use) would be made of plaster. This "negative" image, if properly designed, may be used to produce clay productions, which when fired in a kiln become terra cotta Terra cotta Terra cotta, Terracotta or Terra-cotta is a clay-based unglazed ceramic. Its uses include vessels, water & waste water pipes and surface embellishment in building construction, along with sculpture such as the Terracotta Army and Greek terracotta figurines.... building decorations, or these may be used to create cast concrete Concrete Concrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, construction aggregate , water , and Chemistry admixtures.... sculptures. If a plaster positive was desired this would be constructed or cast to form a durable image artwork. As a model for stonecutters this would be sufficient. If intended for producing a bronze casting the plaster positive could be further worked to produce smooth surfaces. An advantage of this plaster image is that it is relatively cheap; should a patron approve of the durable image and be willing to bear further expense, subsequent molds could be made for the creation of a wax image to be used in lost wax casting Lost wax casting Lost-wax casting, sometimes called by the French_language name of cire perdue or the Latin cera perduta, is the process by which a Bronze_sculpture or brass is Casting from an artist's sculpture; in Industry uses, the modern process is called investment casting.... , a far more expensive process. In lieu of producing a bronze image suitable for outdoor use the plaster image may be painted to resemble a metal image; such sculptures are suitable only for presentation in a weather-protected environment. Plaster expands while hardening, then contracts slightly just before hardening completely. This makes plaster excellent for use in molds, and it is often used as an artistic material for casting. Plaster is also commonly spread over an armature (form), usually made of wire, mesh or other materials. Plaster is often used in faux finishing Faux painting Faux painting or Faux finishing are terms used to describe a wide range of decorative painting techniques. From the French word for "fake", faux painting began as a form of replicating materials such as marble and wood with paint, but has come to encompass many other decorative finishes for walls and furniture.... to create textures for wall and furniture surfaces, as in Venetian Plaster Venetian plaster Venetian Plaster is a Finishing technique using thin layers of plaster applied with a spatula or trowel and then burnished to create a smooth surface with the illusion of depth and texture.... and also in stenciling for raised details. For these processes, artists use limestone based plasters or new user friendly acrylic based plaster. Use in medicine Plaster is widely used as a support for broken bones; a bandage impregnated with plaster is moistened and then wrapped around the damaged limb, setting into a close-fitting yet easily removed tube, known as an orthopedic cast Orthopedic cast An orthopedic cast is a shell, frequently made from plaster, encasing a Limb to hold a broken bone in place until healing is confirmed.Plaster bandages consist of a cotton bandage that has been impregnated with plaster of paris, which hardens after it has been made wet.... ; however, this is slowly being replaced by a fibreglass variety. Plaster is also used within radiotherapy when making immobilization casts for patients. Plaster bandages are used when constructing an impression of the patients head and neck, and liquid plaster is used to fill the impression and produce a plaster bust. Perspex is then vacuum formed over this bust creating an immobilization shell. In dentistry, plaster is used for mounting casts or models of oral tissues. These diagnostic and working models are usually made from dental stone, a stronger, harder and denser derivative of plaster which is manufactured from gypsum under pressure. Plaster is also used to invest or flask wax dentures, the wax being subsequently removed and replaced with the final denture base material which is cured in the plaster mold. Lime plaster Lime plaster is a mixture of calcium hydroxide and sand (or other inert fillers). Carbon dioxide in the atmosphere causes the plaster to set by transforming the calcium hydroxide into calcium carbonate (limestone Limestone File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record.... ). Whitewash Whitewash Whitewash, or calcimine, kalsomine, or calsomine is a very low cost type of paint made from slaked lime and chalk . Various other additives have also been used.... is based on the same chemistry. To make lime plaster, Limestone Limestone File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record.... (calcium carbonate) is heated to produce quicklime (calcium oxide). Water is then added to produce slaked lime (calcium hydroxide), which is sold as a white powder. Additional water is added to form a paste prior to use. The paste may be stored in air-tight containers. Once exposed to the atmosphere, the calcium hydroxide turns back into limestone, causing the plaster to set. Lime plaster is used for true fresco Fresco Fresco is any of several related painting types, done on plaster on walls or ceilings. The word fresco comes from the Italian word affresco which derives from the adjective fresco , which has Latin origins.... es. Pigment Pigment A pigment is a material that changes the color of light it Reflection as the result of selective color absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light.... s, diluted in water, are applied to the still wet plaster. Cement plaster Cement plaster is a mixture of suitable plaster, sand, portland cement Portland cement Portland cement is the most common type of cement in general use around the world, because it is a basic ingredient of concrete, mortar , stucco and most non-specialty grout.... and water which is normally applied to masonry interiors and exteriors to achieve a smooth surface. Interior surfaces sometimes receive a final layer of gypsum plaster. Walls constructed with stock brick London stock brick London stock brick is the most commonly used type of building brick in London. Its distinctive yellow colour and soft appearance comes from the yellow Kent clay from which the bricks are made.... s are normally plastered while face brick Brickwork Brickwork masonry is produced when a bricklayer uses bricks and Mortar to build up structures such as walls, bridges and chimneys. Brickwork is also used to finish openings such as doors or windows in buildings made of other materials.... walls are not plastered. Various cement-based plasters are also used as proprietary spray fireproofing Fireproofing Fireproofing, a passive fire protection measure, refers to the act of making materials or building more resistant to fire, or to those materials themselves, or the act of applying such materials.... products, the world over. These usually use vermiculite Vermiculite Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces.... as lightweight aggregate. Heavy versions of such plasters are also in use for exterior fireproofing, to protect LPG vessels, pipe bridges and vessel skirts. Passive fire protection Plasters have been in use in passive fire protection Passive fire protection Passive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire resistant walls, floors, and doors .... , as fireproofing Fireproofing Fireproofing, a passive fire protection measure, refers to the act of making materials or building more resistant to fire, or to those materials themselves, or the act of applying such materials.... products, for many decades. The finished plaster releases water vapor when exposed to flame, acting to slow the spread of the fire, for as much as an hour or two depending on thickness. It also provides some insulation Thermal insulation The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer.... to retard heat Heat In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic system to another due to a difference in temperature.... flow into structural steel Structural steel Structural steel is steel construction material, a Profile , formed with a specific shape or cross section and certain standards of Chemistry and strength.... elements, that would otherwise lose their strength and collapse in a fire. Early versions of these plasters have used asbestos Asbestos Asbestos is a naturally occurring silicate mineral with long, thin fibrous crystals. The word asbestos is derived from a Greek language adjective meaning inextinguishable.... fibres, which have by now been outlawed in industrialized nations and have caused significant removal Asbestos abatement Many buildings contain asbestos, which was used in spray-applied flame retardant, thermal system insulation, and in a variety of other materials. Asbestos was sometimes "Flocking " above false ceilings, inside technical ducts, and in many other small spaces where firefighters would have difficulty gaining access.... and re-coating work. More modern plasters fall into the following categories: fibrous (including mineral wool Mineral wool Mineral wool, also known as mineral fibers or man-made mineral fibers are fibers made from natural or synthetic minerals or metal oxides.... and glass fiber) cement mixtures either with mineral wool or with vermiculite Vermiculite Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces.... gypsum plasters, leavened with polystyrene Polystyrene Polystyrene , sometimes abbreviated PS, is an Aromaticity polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry.... beads, as well as chemical expansion agents to decrease the density of the finished product One differentiates between interior and exterior fireproofing. Interior products are typically less substantial, with lower densities and lower cost. Exterior products have to withstand more extreme fire and other environmental conditions. Exterior products are also more likely to be attractively tooled, whereas their interior cousins are usually merely sprayed in place. A rough surface is typically forgiven inside of buildings as dropped ceilings often hide them. Exterior fireproofing plasters are losing ground to more costly intumescent Intumescent An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection and, in America, require listing and approval use and compliance in their installed configurations in order to comply with the law.... and endothermic Endothermic In thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs energy in the form of heat. Its etymology stems from the Greek prefix endo-, meaning ?inside? and the Greek suffix ?thermic, meaning ?to heat?.... products, simply on technical merit. Trade jurisdiction on unionized construction sites in North America North America North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere.... remains with the plasterers, regardless of whether the plaster is decorative in nature or is used in passive fire protection. Cementitious and gypsum based plasters tend to be endothermic Endothermic In thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs energy in the form of heat. Its etymology stems from the Greek prefix endo-, meaning ?inside? and the Greek suffix ?thermic, meaning ?to heat?.... . Fireproofing plasters are closely related to firestop Firestop A firestop is a passive fire protection system of various components used to seal Penetration and Joint in Fire-resistance rating wall and/or floor assemblies, based on fire testing and certification listings.... mortars. In fact, most firestop mortars can be sprayed and tooled very well, due to the fine detail work that is required of firestopping, which leads their mix designers to utilise concrete Concrete Concrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, construction aggregate , water , and Chemistry admixtures.... addmixtures, that enable easier tooling than common mortars. Trade jurisdiction In unionized construction sites in North America, plaster is installed by contractors signatory to the Operative Plasterers’ and Cement Masons’ International Association (OPCMIA) Operative Plasterers' and Cement Masons' International Association The Operative Plasterers' and Cement Masons' International Association of the United States and Canada is a trade union that represents plasterers and cement masons in the construction industry in North America.... , which represents unionized plasterer Plasterer A Plasterer is a tradesman who works with plaster, such as forming a layer of plaster on an interior wall or plaster Molding on ceilings or walls.... s. Safety issues The chemical reaction that occurs when plaster is mixed with water is exothermic Exothermic File:Explosion1.JPG In thermodynamics, the term exothermic describes a process or reaction that releases energy usually in the form of heat, but also in form of light , electricity , or sound.... in nature. The danger of this was illustrated in January 2007, when a sixteen-year-old girl suffered third-degree burns after encasing her hands in plaster as part of a school School File:Primary Student of Pakistan.JPGA school , is an institution designed to allow and encourage students to education, under the supervision of teachers.... art Art Art is the process or product of deliberately arranging elements in a way that appeals to the senses or emotions. It encompasses a diverse range of human activities, creations, and modes of expression, including music and literature.... project in Lincolnshire Lincolnshire Lincolnshire is a Counties of England in the east of England. It borders Norfolk, Cambridgeshire, Rutland, Leicestershire, Nottinghamshire, South Yorkshire, and the East Riding of Yorkshire.... , England England native_name =\|conventional_long_name = England\|common_name = England\|image_flag = Flag of England.svg\|image_coat = England COA.svg\|symbol_type = Royal Coat of Arms... . She subsequently had her thumbs and most of her fingers amputated. For this reason only thin layers of plaster should be used, with time to cool between layers, or strips of cloth in plaster laid-up in the method used by the medical field. In place of plaster, alginate can safely be used for casting body parts. Some variations of plaster that contain powdered silica or asbestos Asbestos Asbestos is a naturally occurring silicate mineral with long, thin fibrous crystals. The word asbestos is derived from a Greek language adjective meaning inextinguishable.... may present health hazards if inhaled. Asbestos is a known carcinogen Carcinogen The term carcinogen refers to any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation.... when inhaled in powder form, especially in people who smoke, and inhalation can also cause asbestosis Asbestosis Asbestosis is a chronic Inflammation medical condition affecting the parenchymal Biological tissue of the lungs. It occurs after long-term, heavy exposure to asbestos, e.g.... . Inhaled silica can cause silicosis Silicosis Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust, and is marked by inflammation and scarring in forms of nodular lesions in the upper lobes of the lungs.... and (in very rare cases) can encourage the development of cancer Cancer Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize.... . Persons working regularly with plaster containing these additives should take precautions to avoid inhaling powdered plaster, cured or uncured. (Note that asbestos is rarely used in modern plaster formulations because of its carcinogenic effects.) Special cleanup methods should be used with of plaster products, as they can interfere with the flow of plumbing systems downstream of the disposal area. The residue of these products will often solidify underwater and plug up drains, stain gutters and sidewalks and spoil planting areas. Illegal uses Plaster of Paris has been allegedly used illegally by professional boxers in the past such as Jack Dempsey Jack Dempsey Jack "Manassa Mauler" Dempsey was an United States boxing who held the List of heavyweight boxing champions from 1919 to 1926. Dempsey's aggressive style and punching power made him one of the most popular boxers in history.... . It makes a boxer's taped hands harder. Plaster of Paris has also been used to smuggle cocaine Cocaine Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine.... across the Mexico-United States border. The cocaine powder is mixed with the plaster mixture and sculpted. On May 29, 2008, a 6.6 pound crucifix Crucifix A crucifix is a Christian cross with a representation of Jesus' body, or corpus. It is a principal symbol of the Christianity religion. It is primarily used in the Roman Catholic Church, Anglican churches, and Eastern Orthodox churches, and it emphasizes Christ's sacrifice— his death by crucifixion, which they believe brought about th... sculpture was seized crossing the border when drug-sniffing dogs detected cocaine in the sculpture. Natural occurrence The mineral bassanite is the naturally occurring compound of the formula CaSO₄^.0.5H₂O. It may be found, for example, in some lava Lava Lava is molten Rock expelled by a volcano during an eruption. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 ?C to 1,200 ?C .... s. See also Cast Courts (Victoria and Albert Museum) Cast Courts (Victoria and Albert Museum) File:Another Room of Casts.jpgThe Cast Courts of the Victoria and Albert Museum in London, England, comprise two large halls. Unusually for a museum, the Cast Courts house a collection not of originals, but copies.... Exothermic Exothermic File:Explosion1.JPG In thermodynamics, the term exothermic describes a process or reaction that releases energy usually in the form of heat, but also in form of light , electricity , or sound.... Fireproofing Fireproofing Fireproofing, a passive fire protection measure, refers to the act of making materials or building more resistant to fire, or to those materials themselves, or the act of applying such materials.... Firestop Firestop A firestop is a passive fire protection system of various components used to seal Penetration and Joint in Fire-resistance rating wall and/or floor assemblies, based on fire testing and certification listings.... International Union of Bricklayers and Allied Craftworkers International Union of Bricklayers and Allied Craftworkers The International Union of Bricklayers and Allied Craftworkers is a trade union in the United States and Canada which represents bricklayers, pointers/cleaners/caulkers, stone and marble Stonemasonry, Concrete finisher, plasterers, tilesetters, terrazzo and mosaic workers.... Intumescent Intumescent An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection and, in America, require listing and approval use and compliance in their installed configurations in order to comply with the law.... Intonaco Intonaco Intonaco is an Italian term for the final, very thin layer of plaster on which a fresco wall painting is painted. The painting is done whilst the plaster is still wet, in order to allow the pigment to penetrate into the intonaco itself.... Joint compound Joint compound Joint compound is a white substance similar to plaster used to seal joints between sheets of drywall, primarily in building construction. It is often referred to simply as "mud".... Limestone Limestone File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record.... Passive fire protection Passive fire protection Passive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire resistant walls, floors, and doors .... Pargeting Pargeting Pargeting is a decorative plastering applied to building walls.Pargeting derives from the word 'parget', a Middle English term that is probably derived from the Old French 'pargeter' / 'parjeter', to throw about, or 'porgeter', to roughcast a wall.... Plasterwork Plasterwork Plasterwork refers to construction or ornamentation done with plaster, such as a layer of plaster on an interior wall or plaster Molding on ceilings or walls.... Polished plaster Polished plaster Polished plaster is a term for the finish of some plasters and for the description of new and updated forms of traditional Italian plaster finishes.... Ready-mix lightweight joint compound Stucco Stucco Stucco or render is a material made of an Construction aggregate, a binder , and water. Stucco is applied wet and hardens to a very dense solid.... Venetian Plaster Venetian plaster Venetian Plaster is a Finishing technique using thin layers of plaster applied with a spatula or trowel and then burnished to create a smooth surface with the illusion of depth and texture.... Wattle and daub Wattle and daub Wattle and daub is a building material used for making walls, in which a woven lattice of wooden strips called wattle is daubed with a sticky material usually made of some combination of wet soil, clay, sand, animal dung and straw.... External links