Calcium sulfate (or calcium sulphate ) is the inorganic compound with the formula CaSO 4 and related hydrates . In the form of γ- anhydrite (the anhydrous form), it is used as a desiccant . One particular hydrate is better known as plaster of Paris , and another occurs naturally as the mineral gypsum . It has many uses in industry. All forms are white solids that are poorly soluble in water. Calcium sulfate causes permanent hardness in water.
56-432: The compound exists in three levels of hydration corresponding to different crystallographic structures and to minerals: The main use of calcium sulfate is to produce plaster of Paris and stucco . These applications exploit the fact that calcium sulfate which has been powdered and calcined forms a moldable paste upon hydration and hardens as crystalline calcium sulfate dihydrate. It is also convenient that calcium sulfate
112-489: A coagulant in products such as tofu . For the FDA , it is permitted in cheese and related cheese products; cereal flours; bakery products; frozen desserts; artificial sweeteners for jelly & preserves; condiment vegetables; and condiment tomatoes and some candies. It is known in the E number series as E516 , and the UN's FAO knows it as a firming agent, a flour treatment agent,
168-419: A bone repair cement. Small amounts of calcined gypsum are added to earth to create strong structures directly from cast earth , an alternative to adobe (which loses its strength when wet). The conditions of dehydration can be changed to adjust the porosity of the hemihydrate, resulting in the so-called α- and β-hemihydrates (which are more or less chemically identical). On heating to 180 °C (356 °F),
224-493: A coating for the outside of a building and " plaster " to a coating for interiors. As described below, however, the materials themselves often have little or no difference. Other European languages, notably Italian, do not have the same distinction: stucco means plaster in Italian and serves for both. The basic composition of stucco is lime , water, and sand. The difference in nomenclature between stucco, plaster , and mortar
280-399: A finish layer, which is thinner and faster to apply, compared to the traditional application of three-coat stucco. Imitation stone stucco can also be produced using the traditional application, but with marble dust being added to the mixture. As with any cement-based material, stucco must be reinforced to resist movement cracking. Plastic or wire mesh lath , attached with nails or screws to
336-418: A fire, the structure behind a sheet of drywall will remain relatively cool as water is lost from the gypsum, thus preventing (or substantially retarding) damage to the framing (through combustion of wood members or loss of strength of steel at high temperatures) and consequent structural collapse. But at higher temperatures, calcium sulfate will release oxygen and act as an oxidizing agent . This property
392-433: A sand finish or sprayed. Originally, the lath material was strips of wood installed horizontally on the wall, with spaces between, that would support the wet plaster until it cured. This lath and plaster technique became widely used. In exterior wall applications, the lath is installed over a weather-resistant asphalt - impregnated felt or paper sheet that protects the framing from the moisture that can pass through
448-405: A sequestrant, and a leavening agent. Calcium sulfate has a long history of use in dentistry. It has been used in bone regeneration as a graft material and graft binder (or extender) and as a barrier in guided bone tissue regeneration. It is a biocompatible material and is completely resorbed following implantation. It does not evoke a significant host response and creates a calcium-rich milieu in
504-503: A significant host response and creates a calcium-rich milieu in the area of implantation. When sold at the anhydrous state as a desiccant with a color-indicating agent under the name Drierite , it appears blue (anhydrous) or pink (hydrated) due to impregnation with cobalt(II) chloride , which functions as a moisture indicator. Up to the 1970s, commercial quantities of sulfuric acid were produced from anhydrous calcium sulfate. Upon being mixed with shale or marl , and roasted at 1400°C,
560-402: A solid masonry , brick , or stone surface. The finish coat usually contained an integral color and was typically textured for appearance. Then with the introduction and development of heavy timber and light wood-framed construction methods, stucco was adapted for this new use by adding a reinforcement lattice, or lath , attached to and spanning between the structural supports and by increasing
616-422: A warmer climate (like California , Nevada , Arizona , New Mexico and Florida ), stucco is the predominant exterior for both residential and commercial construction. Stucco exterior (with wood frame interior) became a popular alternative in the southwestern United States during the 1970s, as the masonry labor costs for adobe rose. Stucco has also been used as a sculptural and artistic material. Stucco relief
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#1732852523598672-670: A weaker and brittler stucco. Drierite Calcium sulfate (or calcium sulphate ) is the inorganic compound with the formula CaSO 4 and related hydrates . In the form of γ- anhydrite (the anhydrous form), it is used as a desiccant . One particular hydrate is better known as plaster of Paris , and another occurs naturally as the mineral gypsum . It has many uses in industry. All forms are white solids that are poorly soluble in water. Calcium sulfate causes permanent hardness in water. The compound exists in three levels of hydration corresponding to different crystallographic structures and to minerals: The main use of calcium sulfate
728-513: Is exothermic and is responsible for the ease with which gypsum can be cast into various shapes including sheets (for drywall ), sticks (for blackboard chalk), and molds (to immobilize broken bones, or for metal casting). Mixed with polymers, it has been used as a bone repair cement. Small amounts of calcined gypsum are added to earth to create strong structures directly from cast earth , an alternative to adobe (which loses its strength when wet). The conditions of dehydration can be changed to adjust
784-466: Is also a common component of fouling deposits in industrial heat exchangers, because its solubility decreases with increasing temperature (see the specific section on the retrograde solubility). The solubility of calcium sulfate decreases as temperature increases. This behaviour ("retrograde solubility") is uncommon: dissolution of most of the salts is endothermic and their solubility increases with temperature.The retrograde solubility of calcium sulfate
840-466: Is also a common component of fouling deposits in industrial heat exchangers, because its solubility decreases with increasing temperature (see the specific section on the retrograde solubility). The solubility of calcium sulfate decreases as temperature increases. This behaviour ("retrograde solubility") is uncommon: dissolution of most of the salts is endothermic and their solubility increases with temperature.The retrograde solubility of calcium sulfate
896-425: Is also responsible for its precipitation in the hottest zone of heating systems and for its contribution to the formation of scale in boilers along with the precipitation of calcium carbonate whose solubility also decreases when CO 2 degasses from hot water or can escape out of the system. Stucco Stucco or render is a construction material made of aggregates , a binder , and water. Stucco
952-411: Is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and artistic material in architecture. Stucco can be applied on construction materials such as metal , expanded metal lath , concrete , cinder block , or clay brick and adobe for decorative and structural purposes. In English, "stucco" sometimes refers to
1008-417: Is around 127 million tonnes per annum. In addition to natural sources, calcium sulfate is produced as a by-product in a number of processes: Related sulfur-trapping methods use lime and some produces an impure calcium sulfite , which oxidizes on storage to calcium sulfate. These precipitation processes tend to concentrate radioactive elements in the calcium sulfate product. This issue is particular with
1064-416: Is around 127 million tonnes per annum. In addition to natural sources, calcium sulfate is produced as a by-product in a number of processes: Related sulfur-trapping methods use lime and some produces an impure calcium sulfite , which oxidizes on storage to calcium sulfate. These precipitation processes tend to concentrate radioactive elements in the calcium sulfate product. This issue is particular with
1120-419: Is based more on use than composition. Until the latter part of the nineteenth century, it was common that mortar as well as plaster , which was used inside a building, and stucco, which was used outside, would consist of the same primary materials: lime and sand . Animal or plant fibers were often added for additional strength. Sometimes additives such as acrylics and glass fibers are added to improve
1176-455: Is known in the E number series as E516 , and the UN's FAO knows it as a firming agent, a flour treatment agent, a sequestrant, and a leavening agent. Calcium sulfate has a long history of use in dentistry. It has been used in bone regeneration as a graft material and graft binder (or extender) and as a barrier in guided bone tissue regeneration. It is a biocompatible material and is completely resorbed following implantation. It does not evoke
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#17328525235981232-436: Is poorly soluble in water and does not readily dissolve in contact with water after its solidification. With judicious heating, gypsum converts to the partially dehydrated mineral called bassanite or plaster of Paris . This material has the formula CaSO 4 ·( n H 2 O), where 0.5 ≤ n ≤ 0.8. Temperatures between 100 and 150 °C (212–302 °F) are required to drive off the water within its structure. The details of
1288-429: Is to produce plaster of Paris and stucco . These applications exploit the fact that calcium sulfate which has been powdered and calcined forms a moldable paste upon hydration and hardens as crystalline calcium sulfate dihydrate. It is also convenient that calcium sulfate is poorly soluble in water and does not readily dissolve in contact with water after its solidification. With judicious heating, gypsum converts to
1344-405: Is used in aluminothermy . In contrast to most minerals, which when rehydrated simply form liquid or semi-liquid pastes, or remain powdery, calcined gypsum has an unusual property: when mixed with water at normal (ambient) temperatures, it quickly reverts chemically to the preferred dihydrate form, while physically "setting" to form a rigid and relatively strong gypsum crystal lattice: This reaction
1400-436: Is very hard and brittle and can easily crack and separate from the surcface if the base on which it is applied is not stable. Typically its color was gray, from the innate color of most Portland cement, but white Portland cement is also available. Today's stucco manufacturers offer a very wide range of colors that can be mixed integrally in the finish coat. Other materials such as stone and glass chips are sometimes "dashed" onto
1456-536: Is visually extended into a heavenly architecture with a depiction of Christ , the Virgin Mary or the Last Judgment at the center. Stucco is used to form a semi-plastic extension of the real architecture that merges into the painted architecture. Because of its " aristocratic " appearance, Baroque-looking stucco decoration was used frequently in upper-class apartments of the 19th and early 20th century. Beginning in
1512-440: The arabesque reached its full maturity, carved stucco remained a very common medium for decoration and calligraphic inscriptions. Indian architecture used stucco as a material for sculpture in an architectural context. It is rare in the countryside. In Roman art of the late Republic and early Empire, stucco was used extensively for the decoration of vaults. Though marble was the preferred sculptural medium in most regards, stucco
1568-524: The framing (through combustion of wood members or loss of strength of steel at high temperatures) and consequent structural collapse. But at higher temperatures, calcium sulfate will release oxygen and act as an oxidizing agent . This property is used in aluminothermy . In contrast to most minerals, which when rehydrated simply form liquid or semi-liquid pastes, or remain powdery, calcined gypsum has an unusual property: when mixed with water at normal (ambient) temperatures, it quickly reverts chemically to
1624-444: The 1920s, stucco, especially in its Neo-Renaissance and Neo-Baroque materialization, became increasingly unpopular with modern architects in some countries, resulting not only in new buildings without stucco but also in a widespread Movement [ de ] to remove the stucco from existing tenements. Stucco was still employed in the 1950s in molded forms for decorating the joints between walls and ceilings inside houses. It
1680-468: The Baroque concept that integrates the three classic arts , architecture , sculpture , and painting . The Greco-Buddhist art of modern Afghanistan and northern Pakistan made extensive use in monasteries and temples of stucco for three-dimensional monumental sculpture as well as reliefs. These were usually carved from a rough modelling over a framework and then painted. Similar techniques are used for
1736-440: The area of implantation. When sold at the anhydrous state as a desiccant with a color-indicating agent under the name Drierite , it appears blue (anhydrous) or pink (hydrated) due to impregnation with cobalt(II) chloride , which functions as a moisture indicator. Up to the 1970s, commercial quantities of sulfuric acid were produced from anhydrous calcium sulfate. Upon being mixed with shale or marl , and roasted at 1400°C,
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1792-420: The building as well as in the wall by its excellent permeability- It is more elastic and workable than cement render. Lime itself is usually white; color comes from the aggregate or any added pigments . Lime stucco has the property of being self-healing to a limited degree because of the slight water solubility of lime (which in solution can be deposited in cracks, where it solidifies). Portland cement stucco
1848-495: The completely anhydrous form called β-anhydrite or "natural" anhydrite is formed. Natural anhydrite does not react with water, even over geological timescales, unless very finely ground. The variable composition of the hemihydrate and γ-anhydrite, and their easy inter-conversion, is due to their nearly identical crystal structures containing "channels" that can accommodate variable amounts of water, or other small molecules such as methanol . The calcium sulfate hydrates are used as
1904-458: The finish coat before drying, with the finished product commonly known as "rock dash", "pebble dash", or also as roughcast if the stones are incorporated directly into the stucco, used mainly from the early 20th through the early 21st centuries. As a building material, stucco is a durable, attractive, and weather-resistant wall covering. It was traditionally used as both an interior and exterior finish applied in one or two thin layers directly over
1960-431: The gypsum at this time (the heat of hydration) tends to go into driving off water (as water vapor) rather than increasing the temperature of the mineral, which rises slowly until the water is gone, then increases more rapidly. The equation for the partial dehydration is: The endothermic property of this reaction is relevant to the performance of drywall , conferring fire resistance to residential and other structures. In
2016-555: The hemihydrate and γ-anhydrite, and their easy inter-conversion, is due to their nearly identical crystal structures containing "channels" that can accommodate variable amounts of water, or other small molecules such as methanol . The calcium sulfate hydrates are used as a coagulant in products such as tofu . For the FDA , it is permitted in cheese and related cheese products; cereal flours; bakery products; frozen desserts; artificial sweeteners for jelly & preserves; condiment vegetables; and condiment tomatoes and some candies. It
2072-463: The life-size statues decorating the gopurams of Hindu temples in modern South Asia . Since stucco can be used for decoration as well as for figurative representation, it provides an ideal transitive link from architectural details to wall paintings such as the typically Baroque trompe-l'œil ceilings, as in the work of the Wessobrunner School . Here, the real architecture of the church
2128-479: 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, the completely anhydrous form called β-anhydrite or "natural" anhydrite is formed. Natural anhydrite does not react with water, even over geological timescales, unless very finely ground. The variable composition of
2184-508: The partially dehydrated mineral called bassanite or plaster of Paris . This material has the formula CaSO 4 ·( n H 2 O), where 0.5 ≤ n ≤ 0.8. Temperatures between 100 and 150 °C (212–302 °F) are required to drive off the water within its structure. The details of the temperature and time depend on ambient humidity. Temperatures as high as 170 °C (338 °F) are used in industrial calcination, but at these temperatures γ-anhydrite begins to form. The heat energy delivered to
2240-428: The phosphate by-product, since phosphate ores naturally contain uranium and its decay products such as radium-226 , lead-210 and polonium-210 . Extraction of uranium from phosphorus ores can be economical on its own depending on prices on the uranium market or the separation of uranium can be mandated by environmental legislation and its sale is used to recover part of the cost of the process. Calcium sulfate
2296-425: The phosphate by-product, since phosphate ores naturally contain uranium and its decay products such as radium-226 , lead-210 and polonium-210 . Extraction of uranium from phosphorus ores can be economical on its own depending on prices on the uranium market or the separation of uranium can be mandated by environmental legislation and its sale is used to recover part of the cost of the process. Calcium sulfate
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2352-429: The plaster something to attach to and to add strength. Types include expanded-metal lath, woven-wire lath, and welded-wire lath. If applied during very dry weather, the layers of stucco are sprayed with water for one or more days to keep a level of moisture within the stucco while it cures, a process known as "moist curing". If the stucco dries too soon, the chemical hardening ("hydration") will be incomplete, resulting in
2408-431: The porosity of the hemihydrate, resulting in the so-called α- and β-hemihydrates (which are more or less chemically identical). On heating to 180 °C (356 °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,
2464-465: The porous stucco. Following World War II , the introduction of metal wire mesh , or netting, replaced the use of wood lath. Galvanizing the wire made it corrosion resistant and suitable for exterior wall applications. At the beginning of the 21st century, this "traditional" method of wire mesh lath and three coats of exterior plaster was still widely used. In some parts of the United States with
2520-400: The preferred dihydrate form, while physically "setting" to form a rigid and relatively strong gypsum crystal lattice: This reaction is exothermic and is responsible for the ease with which gypsum can be cast into various shapes including sheets (for drywall ), sticks (for blackboard chalk), and molds (to immobilize broken bones, or for metal casting). Mixed with polymers, it has been used as
2576-486: The structural framing, is embedded into the base coat to provide stiffening for the stucco. Where stucco is to be applied to a structure of wood-framing or light-gauge steel framing, the framing is protected from moisture damage by applying a cement based primer, or a vapor-permeable, water-resistant weather barrier; typically an asphalt -saturated paper or one of a variety of manufactured plastic-based sheets, known as " building wraps " or "stucco wraps". The properties of
2632-487: The structural properties of the stucco. This is usually done with what is considered a one-coat stucco system, as opposed to the traditional three-coat method. In the latter nineteenth century, Portland cement was added with increasing frequency to cover surfaces in contact with soil or water. At the same time, traditional lime plasters were often being replaced by gypsum plaster. Lime is almost as good in balancing humidity as clay. It prevents moisture accumulation inside
2688-466: The sulfate liberates sulfur dioxide gas, a precursor to sulfuric acid . The reaction also produces calcium silicate , used in cement clinker production. Some component reactions pertaining to calcium sulfate: The main sources of calcium sulfate are naturally occurring gypsum and anhydrite , which occur at many locations worldwide as evaporites . These may be extracted by open-cast quarrying or by deep mining. World production of natural gypsum
2744-464: The sulfate liberates sulfur dioxide gas, a precursor to sulfuric acid . The reaction also produces calcium silicate , used in cement clinker production. Some component reactions pertaining to calcium sulfate: The main sources of calcium sulfate are naturally occurring gypsum and anhydrite , which occur at many locations worldwide as evaporites . These may be extracted by open-cast quarrying or by deep mining. World production of natural gypsum
2800-402: The temperature and time depend on ambient humidity. Temperatures as high as 170 °C (338 °F) are used in industrial calcination, but at these temperatures γ-anhydrite begins to form. The heat energy delivered to the gypsum at this time (the heat of hydration) tends to go into driving off water (as water vapor) rather than increasing the temperature of the mineral, which rises slowly until
2856-493: The thickness and number of layers of the total system. The lath added support for the wet plaster and tensile strength to the brittle, cured stucco; while the increased thickness and number of layers helped control cracking. The traditional application of stucco and lath occurs in three coats—the scratch coat, the brown coat and the finish coat. The two base coats of plaster are either hand-applied or machine sprayed. The finish coat can be troweled smooth, hand-textured, floated to
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#17328525235982912-416: The water is gone, then increases more rapidly. The equation for the partial dehydration is: The endothermic property of this reaction is relevant to the performance of drywall , conferring fire resistance to residential and other structures. In a fire, the structure behind a sheet of drywall will remain relatively cool as water is lost from the gypsum, thus preventing (or substantially retarding) damage to
2968-404: The weather barrier must not only protect the framing from rain and moisture, but at the same time allow the free passage of any water vapor generated inside the building to escape through the wall. A wide variety of stucco accessories, such as weep screeds , control and expansion joints, corner-aids and architectural reveals are sometimes also incorporated into the lath. Wire lath is used to give
3024-422: Was better for use in vaults because it was lighter and better suited to adapt to the curvature of the ceiling. Baroque and Rococo architecture makes heavy use of stucco. Examples can be found in churches and palaces, where stucco is mostly used to provide a smooth, decorative transition from walls to ceiling, decorating and giving measure to ceiling surfaces. Stucco is an integral part of the art of belcomposto ,
3080-453: Was generally painted the same colour as the ceiling and used in designs where a picture rail or rat rail was in use. Modern stucco is used as an exterior cement plaster wall covering. It is usually a mix of sand , Portland cement , lime and water, but may also consist of a proprietary mix of additives including fibers and synthetic acrylics that add strength and flexibility. Modern synthetic stucco can be applied as one base layer and
3136-472: Was used in the architectural decoration schemes of many ancient cultures. Examples of Egyptian , Minoan , and Etruscan stucco reliefs remain extant. In the art of Mesopotamia and ancient Persian art there was a widespread tradition of figurative and ornamental internal stucco reliefs, which continued into Islamic art , for example in Abbasid Samarra , now using geometrical and plant-based ornament. As
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