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77-740: The Kalkberg was mined for salt until 1860 and was the site of a gypsum quarry until 1931. After the Nazis came to power, the quarry was converted into an amphitheatre to be used for mass meetings and multimedia theatrical performances as part of the Thingspiel movement. The theatre was designed by Fritz Schaller of Berlin, and was constructed mostly by the Reich Labour Service beginning on 29 May 1934. The work entailed sealing salt-mining shafts and cavities and bringing in 1,200 tonnes of granite from Silesia as building material, since

154-427: A recommended exposure limit (REL) of TWA 10 mg/m for total exposure and TWA 5 mg/m for respiratory exposure over an eight-hour workday. Gypsum is used in a wide variety of applications: Plaster of Paris Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means

231-425: A detergent agent (such as sodium dodecylbenzene sulfonate ). 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. In modern days this material is also used for false ceiling . In this,

308-512: A fertilizer. Gypsum may act as a source of sulfur for plant growth, and in the early 19th century, it was regarded as an almost miraculous fertilizer. American farmers were so anxious to acquire it that a lively smuggling trade with Nova Scotia evolved, resulting in the so-called "Plaster War" of 1820. Gypsum is moderately water-soluble (~2.0–2.5 g/L at 25 °C) and, in contrast to most other salts, it exhibits retrograde solubility, becoming less soluble at higher temperatures. When gypsum

385-403: A fire. Early versions of protective plasters often contain asbestos fibres, which since have been outlawed in many industrialized nations. Recent plasters for fire protection either contain cement or gypsum as binding agents as well as mineral wool or glass fiber to add mechanical strength. Vermiculite , polystyrene beads or chemical expansion agents are often added to decrease the density of

462-455: A hand-made and pleasing textured alternative to machine-made modern substrate finishes. But clay plaster finishes are rare and fleeting. According to Martin Weaver, "Many of North America's historic building interiors … are all too often … one of the first things to disappear in the frenzy of demolition of interiors which has unfortunately come to be a common companion to 'heritage preservation' in

539-400: A hidden supporting framework. Forms of plaster have several other uses. In medicine, plaster orthopedic casts are still often used for supporting set broken bones. In dentistry, plaster is used to make dental models by pouring the material into dental impressions . Various types of models and moulds are made with plaster. In art, lime plaster is the traditional matrix for fresco painting;

616-467: A lime and sand mortar to provide a weather proof seal to protect from water penetration. This allowed a rendering of clay plaster and setting coat of thin lime and fine sand on exterior-walled rooms. Split lath was nailed with square cut lath nails, one into each framing member. With hand split lath the plasterer had the luxury of making lath to fit the cavity being plastered. Lengths of lath two to six foot are not uncommon at Economy Village. Hand split lath

693-401: A material used for the interiors of buildings, while "render" commonly refers to external applications. The term stucco refers to plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces. The most common types of plaster mainly contain either gypsum , lime , or cement , but all work in a similar way. The plaster is manufactured as a dry powder and

770-622: A mixture of suitable plaster, sand, Portland cement 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 bricks are normally plastered while face brick walls are not plastered. Various cement-based plasters are also used as proprietary spray fireproofing products. These usually use vermiculite as lightweight aggregate. Heavy versions of such plasters are also in use for exterior fireproofing, to protect LPG vessels, pipe bridges and vessel skirts. Cement plaster

847-471: A patient's head and neck, and liquid plaster is used to fill the impression and produce a plaster bust. The transparent material polymethyl methacrylate (Plexiglas, Perspex) is then vacuum formed over this bust to create a clear face mask which will hold the patient's head steady while radiation is being delivered. In dentistry, plaster is used for mounting casts or models of oral tissues. These diagnostic and working models are usually made from dental stone,

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924-454: 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

1001-410: A plaster secondary support. Some, like Michelangelo's Sistine Chapel ceiling , are executed in fresco , meaning they are painted on a thin layer of wet plaster, called intonaco ; 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

1078-407: A positive model of the limb and used in fabricating the final medical device. In addition, dentures (false teeth) are made by first taking a dental impression using a soft, pliable material that can be removed from around the teeth and gums without loss of fidelity and using the impression to creating a wax model of the teeth and gums. The model is used to create a plaster mold (which is heated so

1155-400: 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. Lime plaster is used for frescoes , where pigments , diluted in water, are applied to the still wet plaster. USA and Iran are the main plaster producers in the world. Cement plaster is

1232-474: A range of industrial processes. Flue gas desulfurization gypsum (FGDG) is recovered at some coal-fired power plants. The main contaminants are Mg, K, Cl, F, B, Al, Fe, Si, and Se. They come both from the limestone used in desulfurization and from the coal burned. This product is pure enough to replace natural gypsum in a wide variety of fields including drywalls, water treatment, and cement set retarder. Improvements in flue gas desulfurization have greatly reduced

1309-420: A remarkable property of setting into a hard mass on wetting with water. CaSO 4 ⋅ 1 2 H 2 O + 1 1 2 H 2 O ⟶ CaSO 4 ⋅ 2 H 2 O {\displaystyle {\ce {CaSO4.1/2H2O + 1 1/2H2O -> CaSO4.2H2O}}} Plaster of Paris

1386-413: A result, waste gypsum is stored in stacks indefinitely, with significant risk of leaching their contaminants into water and soil. To reduce the accumulation and ultimately clear out these stacks, research is underway to find more applications for such waste products. People can be exposed to gypsum in the workplace by breathing it in, skin contact, and eye contact. Calcium sulfate per se is nontoxic and

1463-431: A rigid denture base. Moreover, in dentistry there are 5 types of gypsum products depending on their consistency and uses: 1) impression plaster (type 1), 2) model plaster (type 2), dental stones (types 3, 4 and 5) In orthotics and prosthetics, plaster bandages traditionally were used to create impressions of the patient's limb (or residuum). This negative impression was then, itself, filled with plaster of Paris, to create

1540-523: A sledge. When small enough, a froe and mallet were used to split away narrow strips of lath. Farm animals provided hair and manure for the float coat of plaster. Fields of wheat and grains provided straw and hay to reinforce the clay plaster. But there was no uniformity in clay plaster recipes. Manure provides fiber for tensile strength as well as protein adhesive. Unlike casein used with lime plaster, hydrogen bonds of manure proteins are weakened by moisture. With braced timber-framed structures clay plaster

1617-416: A stronger, harder and denser derivative of plaster which is manufactured from gypsum under pressure. Plaster is also used to invest and flask wax dentures, the wax being subsequently removed by "burning out," and replaced with flowable denture base material. The typically acrylic denture base then cures in the plaster investment mold. Plaster investments can withstand the high heat and pressure needed to ensure

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1694-543: A wide range of colors to local deposits. Because gypsum dissolves over time in water, gypsum is rarely found in the form of sand. However, the unique conditions of the White Sands National Park in the US state of New Mexico have created a 710 km (270 sq mi) expanse of white gypsum sand, enough to supply the US construction industry with drywall for 1,000 years. Commercial exploitation of

1771-590: Is a mixture of clay , sand and water often with the addition of plant fibers for tensile strength over wood lath . Clay plaster has been used around the world at least since antiquity. Settlers in the American colonies used clay plaster on the interiors of their houses: "Interior plastering in the form of clay antedated even the building of houses of frame, and must have been visible in the inside of wattle filling in those earliest frame houses in which … wainscot had not been indulged. Clay continued in use long after

1848-727: Is a soft sulfate mineral composed of calcium sulfate dihydrate , with the chemical formula CaSO 4 ·2H 2 O . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster , drywall and blackboard or sidewalk chalk . Gypsum also crystallizes as translucent crystals of selenite . It forms as an evaporite mineral and as a hydration product of anhydrite . The Mohs scale of mineral hardness defines gypsum as hardness value 2 based on scratch hardness comparison . Fine-grained white or lightly tinted forms of gypsum known as alabaster have been used for sculpture by many cultures including Ancient Egypt , Mesopotamia , Ancient Rome ,

1925-462: Is accompanied by a slight expansion of volume. It is used in making casts for statues, toys , and more. The initial matrix consists mostly of orthorhombic crystals: the kinetic product. Over the next 72 hours, the rhombic crystals give way to an interlocking mass of monoclinic crystal needles, and the plaster increases in hardness and strength. If plaster or gypsum is heated to between 130 °C (266 °F) and 180 °C (350 °F), hemihydrate

2002-525: Is commonly based on the reaction of gypsum plaster with water, where the water is selectively applied by the inkjet head. The chemical reaction that occurs when plaster is mixed with water is exothermic . When plaster sets, it can reach temperatures of more than 60 °C (140 °F) and, in large volumes, can burn the skin. In January 2007, a secondary school student in Lincolnshire , England sustained third-degree burns after encasing her hands in

2079-510: Is contaminated by impurities found in the rock, namely fluoride , silica , radioactive elements such as radium , and heavy metal elements such as cadmium . Similarly, production of titanium dioxide produces titanium gypsum (TG) due to neutralization of excess acid with lime . The product is contaminated with silica, fluorides, organic matters, and alkalis. Impurities in refinery gypsum waste have, in many cases, prevented them from being used as normal gypsum in fields such as construction. As

2156-448: Is even approved as a food additive, but as powdered gypsum, it can irritate skin and mucous membranes. The Occupational Safety and Health Administration (OSHA) has set the legal limit ( permissible exposure limit ) for gypsum exposure in the workplace as TWA 15 mg/m for total exposure and TWA 5 mg/m for respiratory exposure over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set

2233-456: Is formed, which will also re-form as gypsum if mixed with water. On heating to 180 °C (350 °F), the nearly water-free form, called γ-anhydrite (CaSO 4 · n H 2 O where n = 0 to 0.05) is produced. γ-anhydrite reacts slowly with water to return to the dihydrate state, a property exploited in some commercial desiccants . On heating above 250 °C (480 °F), the completely anhydrous form called β-anhydrite or dead burned plaster

2310-436: Is formed. 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 ). Whitewash is based on the same chemistry. To make lime plaster, limestone (calcium carbonate) is heated above approximately 850 °C (1600 °F) to produce quicklime (calcium oxide). Water

2387-735: Is generally less durable. Plaster (often called stucco in this context) is a far easier material for making reliefs than stone or wood, and was widely used for large interior wall-reliefs in Egypt and the Near East from antiquity into Islamic times (latterly for architectural decoration, as at the Alhambra ), Rome, and Europe from at least the Renaissance, as well as probably elsewhere. However, it needs very good conditions to survive long in unmaintained buildings – Roman decorative plasterwork

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2464-593: Is heated in air it loses water and converts first to calcium sulfate hemihydrate ( bassanite , often simply called "plaster") and, if heated further, to anhydrous calcium sulfate ( anhydrite ). As with anhydrite , the solubility of gypsum in saline solutions and in brines is also strongly dependent on sodium chloride (common table salt) concentration. The structure of gypsum consists of layers of calcium (Ca ) and sulfate ( SO 2− 4 ) ions tightly bound together. These layers are bonded by sheets of anion water molecules via weaker hydrogen bonding , which gives

2541-490: Is mainly known from Pompeii and other sites buried by ash from Mount Vesuvius . Plaster may be cast directly into a damp clay mold. In creating this piece molds (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 building decorations, or these may be used to create cast concrete sculptures. If

2618-500: Is mixed with water to form a stiff but workable paste immediately before it is applied to the surface. The reaction with water liberates heat through crystallization and the hydrated plaster then hardens. Plaster can be relatively easily worked with metal tools and sandpaper and can be moulded, either on site or in advance, and worked pieces can be put in place with adhesive . Plaster is suitable for finishing rather than load-bearing, and when thickly applied for decoration may require

2695-477: Is not uniform like sawn lath. The straightness or waviness of the grain affected the thickness or width of each lath, and thus the spacing of the lath. The clay plaster rough coat varied to cover the irregular lath. Window and door trim as well as the mudboard (baseboard) acted as screeds. With the variation of the lath thickness and use of coarse straw and manure, the clay coat of plaster was thick in comparison to later lime-only and gypsum plasters. In Economy Village,

2772-594: Is often used as an artistic material for casting. Plaster is also commonly spread over an armature (form), made of wire mesh, cloth, or other materials; a process for adding raised details. For these processes, limestone or acrylic based plaster may be employed, known as stucco. Products composed mainly of plaster of Paris and a small amount of Portland cement are used for casting sculptures and other art objects as well as molds. Considerably harder and stronger than straight plaster of Paris, these products are for indoor use only as they degrade in moist conditions. Plaster

2849-462: Is prized for ornamental work of various sorts. In arid areas, gypsum can occur in a flower-like form, typically opaque, with embedded sand grains called desert rose . It also forms some of the largest crystals found in nature, up to 12 m (39 ft) long, in the form of selenite. Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks . Deposits are known to occur in strata from as far back as

2926-533: Is produced by heating gypsum to about 120–180 °C (248–356 °F) in a kiln: CaSO 4 ⋅ 2 H 2 O ⟶ heat CaSO 4 ⋅ 1 2 H 2 O + 1 1 2 H 2 O ↑ {\displaystyle {\ce {CaSO4.2H2O {\overset {heat}{{}->{}}}{CaSO4.1/2H2O}+ 1\!1/2 H2O ^}}} (released as steam). Plaster of Paris has

3003-419: Is stored in moisture -proof containers, because the presence of moisture can cause slow setting of plaster of Paris by bringing about its hydration, which will make it useless after some time. When the dry plaster powder is mixed with water, it rehydrates over time into gypsum. The setting of plaster slurry starts about 10 minutes after mixing and is complete in about 45 minutes. The setting of plaster of Paris

3080-421: Is then added to produce slaked lime (calcium hydroxide), which is sold as a wet putty or a white powder. Additional water is added to form a paste prior to use. The paste may be stored in airtight containers. When exposed to the atmosphere, the calcium hydroxide very slowly turns back into calcium carbonate through reaction with atmospheric carbon dioxide, causing the plaster to increase in strength. Lime plaster

3157-476: Is to find lime, bricks, clay, stone, haire, together with laborers and workmen." Records of the New Haven colony in 1641 mention clay and hay as well as lime and hair also. In German houses of Pennsylvania the use of clay persisted. Old Economy Village is one such German settlement. The early Nineteenth-Century utopian village in present-day Ambridge , Pennsylvania, used clay plaster substrate exclusively in

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3234-400: Is to replace conventional gypsum plasters in cases where the temperature can get too high for gypsum plaster to stay on the wall or ceiling. An example of a heat-resistant plaster composition is a mixture of Portland cement , gypsum, lime, exfoliated insulating aggregate ( perlite and vermiculite or mica ), phosphate shale , and small amounts of adhesive binder (such as Gum karaya ), and

3311-503: Is used. The walls are painted with the plaster which (in some countries) is nothing but calcium carbonate. After drying the calcium carbonate plaster turns white and then the wall is ready to be painted. Elsewhere in the world, such as the UK, ever finer layers of plaster are added on top of the plasterboard (or sometimes the brick wall directly) to give a smooth brown polished texture ready for painting. Mural paintings are commonly painted onto

3388-401: 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 . Plaster is also used in preparation for radiotherapy when fabricating individualized immobilization shells for patients. Plaster bandages are used to construct an impression of

3465-498: The Archaean eon . Gypsum is deposited from lake and sea water, as well as in hot springs , from volcanic vapors, and sulfate solutions in veins . Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures. It is often associated with the minerals halite and sulfur . Gypsum is the most common sulfate mineral. Pure gypsum is white, but other substances found as impurities may give

3542-717: The Byzantine Empire , and the Nottingham alabasters of Medieval England . The word gypsum is derived from the Greek word γύψος ( gypsos ), "plaster". Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum ( calcined gypsum) used for various purposes, this dehydrated gypsum became known as plaster of Paris . Upon adding water, after a few dozen minutes, plaster of Paris becomes regular gypsum (dihydrate) again, causing

3619-790: The Mars Reconnaissance Orbiter (MRO) have indicated the existence of gypsum dunes in the northern polar region of Mars, which were later confirmed at ground level by the Mars Exploration Rover (MER) Opportunity . Commercial quantities of gypsum are found in the cities of Araripina and Grajaú in Brazil; in Pakistan, Jamaica, Iran (world's second largest producer), Thailand, Spain (the main producer in Europe), Germany, Italy, England, Ireland, Canada and

3696-474: The Middle East at least 7,000 years ago. In Egypt, gypsum was burned in open fires, crushed into powder, and mixed with water to create plaster, used as a mortar between the blocks of pyramids and to provide a smooth wall facing. In Jericho, a cult arose where human skulls were decorated with plaster and painted to appear lifelike. The Romans brought plaster-work techniques to Europe . Clay plaster

3773-528: The anhydrite core of the hill itself is water-soluble. The theatre was dedicated on 10 October 1937 by Joseph Goebbels as the Feierstätte der Nordmark or Nordmark-Feierstätte (Northern March Ceremonial Site); in his speech he expressed the wish it would be a "political church of National Socialism". A performance of Henrik Herse 's Die Schlacht der weißen Schiffe took place there, probably in 1938, but after that there were no further performances until

3850-700: The United States. Large open pit quarries are located in many places including Fort Dodge, Iowa , which sits on one of the largest deposits of gypsum in the world, and Plaster City, California , United States, and East Kutai , Kalimantan , Indonesia. Several small mines also exist in places such as Kalannie in Western Australia , where gypsum is sold to private buyers for additions of calcium and sulfur as well as reduction of aluminum toxicities on soil for agricultural purposes. Crystals of gypsum up to 11 m (36 ft) long have been found in

3927-443: The adoption of laths and brick filling for the frame." Where lime was not easily accessible it was rationed and usually substituted with clay as a binder. In Martin E. Weaver 's seminal work he says, "Mud plaster consists of clay or earth which is mixed with water to give a 'plastic' or workable consistency. If the clay mixture is too plastic it will shrink, crack and distort on drying. Sand, fine gravels and fibres were added to reduce

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4004-495: The amount of toxic elements present. Gypsum precipitates onto brackish water membranes , a phenomenon known as mineral salt scaling , such as during brackish water desalination of water with high concentrations of calcium and sulfate . Scaling decreases membrane life and productivity. This is one of the main obstacles in brackish water membrane desalination processes, such as reverse osmosis or nanofiltration . Other forms of scaling, such as calcite scaling, depending on

4081-418: The area, strongly opposed by area residents, was permanently prevented in 1933 when President Herbert Hoover declared the gypsum dunes a protected national monument . Gypsum is also formed as a by-product of sulfide oxidation , amongst others by pyrite oxidation , when the sulfuric acid generated reacts with calcium carbonate . Its presence indicates oxidizing conditions. Under reducing conditions,

4158-458: The brick and wood frame high architecture of the Feast Hall, Great House and other large and commercial structures as well as in the brick, frame and log dwellings of the society members. The use of clay in plaster and in laying brickwork appears to have been a common practice at that time not just in the construction of Economy village when the settlement was founded in 1824. Specifications for

4235-489: The caves of the Naica Mine of Chihuahua , Mexico. The crystals thrived in the cave's extremely rare and stable natural environment. Temperatures stayed at 58 °C (136 °F), and the cave was filled with mineral-rich water that drove the crystals' growth. The largest of those crystals weighs 55 tonnes (61 short tons) and is around 500,000 years old. Synthetic gypsum is produced as a waste product or by-product in

4312-475: The concentrations of fine clay particles which were the cause of the excessive shrinkage." Manure was often added for its fibre content. In some building techniques straw or grass was used as reinforcement. In the Earliest European settlers' plasterwork, a mud plaster was used McKee wrote, of a circa 1675 Massachusetts contract that specified the plasterer, "Is to lath and siele the four rooms of

4389-465: The construction of, "Lock keepers houses on the Chesapeake and Ohio Canal, written about 1828, require stone walls to be laid with clay mortar, excepting 3 inches on the outside of the walls … which (are) to be good lime mortar and well pointed." The choice of clay was because of its low cost, but also the availability. At Economy, root cellars dug under the houses yielded clay and sand (stone), or

4466-445: The creation of a wax image to be used in lost wax 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

4543-672: The crystal perfect cleavage along the sheets (in the {010} plane). Gypsum occurs in nature as flattened and often twinned crystals , and transparent, cleavable masses called selenite . Selenite contains no significant selenium ; rather, both substances were named for the ancient Greek word for the Moon . Selenite may also occur in a silky, fibrous form, in which case it is commonly called "satin spar". Finally, it may also be granular or quite compact. In hand-sized samples, it can be anywhere from transparent to opaque. A very fine-grained white or lightly tinted variety of gypsum, called alabaster ,

4620-669: The end of World War II. Immediately after the war, the arena was used amongst other things for boxing and for circus performances, before becoming the site of the Karl May Festival in 1952. Concerts also take place there, including Norddeutscher Rundfunk 's annual Kult am Kalkberg . With the Berlin Waldbühne and the Freilichtbühne Loreley , it is one of the best known of the former Thing sites. Schaller did not do any further blasting, but used

4697-548: The existing shape of the quarry, so the arena is asymmetrical and has a smaller stage area to one side. There is a rocky peak behind the stage, and loudspeakers were not installed because of the natural amplification. Originally there was to have been a monument behind the theatre. 14,000 seats and room for 6,000 standees were planned, but the theatre as built seats 10,000 and has room for 4,000 standees. 53°56′07″N 10°19′03″E  /  53.9354°N 10.3176°E  / 53.9354; 10.3176 Gypsum Gypsum

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4774-639: The finished product and increase thermal insulation. One differentiates between interior and exterior fireproofing. Interior products are typically less substantial, with lower densities and lower cost. Exterior products have to withstand harsher environmental conditions. A rough surface is typically forgiven inside of buildings as dropped ceilings often hide them. Fireproofing plasters are losing ground to more costly intumescent and endothermic products, simply on technical merit. Trade jurisdiction on unionized construction sites in North America remains with

4851-441: The guise of building rehabilitation." Gypsum plaster, also known as plaster of Paris , is a white powder consisting of calcium sulfate hemihydrate . The natural form of the compound is the mineral bassanite . The name "plaster of Paris" was given because it was originally made by heating gypsum from a large deposit at Montmartre , a hill in the north end of Paris . Gypsum plaster, gypsum powder, or plaster of Paris,

4928-450: The house betwixt the joists overhead with a coat of lime and haire upon the clay; also to fill the gable ends of the house with ricks and plaister them with clay. 5. To lath and plaster partitions of the house with clay and lime, and to fill, lath, and plaister them with lime and haire besides; and to siele and lath them overhead with lime; also to fill, lath, and plaster the kitchen up to the wall plate on every side. 6. The said Daniel Andrews

5005-489: The lime top coats are thin veneers often an eighth inch or less attesting to the scarcity of limestone supplies there. Clay plasters with their lack of tensile and compressive strength fell out of favor as industrial mining and technology advances in kiln production led to the exclusive use of lime and then gypsum in plaster applications. However, clay plasters still exist after hundreds of years clinging to split lath on rusty square nails. The wall variations and roughness reveal

5082-586: The material to harden or "set" in ways that are useful for casting and construction. Gypsum was known in Old English as spærstān , "spear stone", referring to its crystalline projections. Thus, the word spar in mineralogy, by comparison to gypsum, refers to any non- ore mineral or crystal that forms in spearlike projections. In the mid-18th century, the German clergyman and agriculturalist Johann Friderich Mayer investigated and publicized gypsum's use as

5159-480: 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 , also composed mostly of gypsum plaster. In both these methods,

5236-403: The nearby Ohio river yielded washed sand from the sand bars; and lime outcroppings and oyster shell for the lime kiln . The surrounding forests of the new village of Economy provided straight grain, old- growth oak trees for lath. Hand split lath starts with a log of straight grained wood of the required length. The log is split into quarters and then smaller and smaller bolts with wedges and

5313-413: The pigments are applied to a thin wet top layer of plaster and fuse with it so that the painting is actually in coloured plaster. In the ancient world, as well as the sort of ornamental designs in plaster relief that are still used, plaster was also widely used to create large figurative reliefs for walls, though few of these have survived. Plaster was first used as a building material and for decoration in

5390-403: 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. Fireproofing plasters are closely related to firestop mortars. Most firestop mortars can be sprayed and tooled very well, due to the fine detail work that is required of firestopping. Powder bed and inkjet head 3D printing

5467-453: The powder form is converted in a sheet form and the sheet is then attached to the basic ceiling with the help of fasteners. It is done in various designs containing various combinations of lights and colors. The common use of this plaster can be seen in the construction of houses. Post-construction, direct painting is possible (which is commonly seen in French architecture), but elsewhere plaster

5544-451: The sulfates it contains can be reduced back to sulfide by sulfate-reducing bacteria . This can lead to accumulation of elemental sulfur in oil-bearing formations, such as salt domes, where it can be mined using the Frasch process Electric power stations burning coal with flue gas desulfurization produce large quantities of gypsum as a byproduct from the scrubbers. Orbital pictures from

5621-561: The water source, can also be important considerations in distillation , as well as in heat exchangers , where either the salt solubility or concentration can change rapidly. A new study has suggested that the formation of gypsum starts as tiny crystals of a mineral called bassanite (2CaSO 4 ·H 2 O). This process occurs via a three-stage pathway: The production of phosphate fertilizers requires breaking down calcium-containing phosphate rock with acid, producing calcium sulfate waste known as phosphogypsum (PG). This form of gypsum

5698-582: The wax melts and flows out) and the denture materials are injected into the mold. After a curing period, the mold is opened and the dentures are cleaned up and polished. Plasters have been in use in passive fire protection , as fireproofing products, for many decades. Gypsum 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. Plaster also provides some insulation to retard heat flow into structural steel elements, that would otherwise lose their strength and collapse in

5775-431: Was a common building material for wall surfaces in a process known as lath and plaster , whereby a series of wooden strips on a studwork 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 , with a cure time of about a month. To stabilize the lime plaster during curing, small amounts of plaster of Paris were incorporated into

5852-464: Was first introduced in America around 1909 and was often called by the generic name adamant plaster after a prominent manufacturer of the time. The advantages of cement plaster noted at that time were its strength, hardness, quick setting time and durability. Heat-resistant plaster is a building material used for coating walls and chimney breasts and for use as a fire barrier in ceilings. Its purpose

5929-424: Was used on interior walls and ceilings as well as exterior walls as the wall cavity and exterior cladding isolated the clay plaster from moisture penetration. Application of clay plaster in brick structures risked water penetration from failed mortar joints on the exterior brick walls. In Economy Village, the rear and middle wythes of brick dwelling walls are laid in a clay and sand mortar with the front wythe bedded in

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