Plaster are building materials used for protective and/or wall and ceiling coatings and for printing and printing decorative elements. In English "plaster" usually means the material used for building interiors, while "rendering" usually refers to external applications. Another imprecise term used for materials is plastering, which is also often used for plaster that works in several ways to produce decorative reliefs, rather than flat surfaces.
The most common type of plaster mainly contains gypsum, lime, or cement, but all work in the same way. The plaster is made as a dry powder and mixed with water to form a rigid paste but can be used immediately before it is applied to the surface. The reaction with water frees the heat through crystallization and the hydrated plaster then solidifies.
Plaster can be relatively easy to work with metal tools or even sandpaper, and can be formed either on site or to create preformed parts mounted with adhesive. Plaster is not a strong material; very suitable for finishing, not load, and when thick applied to decoration may require hidden support framework, usually in metal.
Plaster form has several other uses. In the treatment of orthopedic cast is often still used to support fractures. In dentistry plaster is used to make a tooth model. Different types of models and prints are made with plaster. In art, lime plaster is a traditional matrix for fresco painting; pigment was applied to a thin layer of wet plaster and blended with it so that the painting was completely stained with plaster. In the ancient world, as well as the kind of ornamental designs in plaster reliefs that are still in use, plaster is also widely used to make large figurative reliefs for walls, although few survive.
Video Plaster
Type
Clay Plaster
Clay plaster is a mixture of clay, sand and water with the addition of plant fibers for tensile strength over wooden battens.
Clay plaster has been used since antiquity. Settlers in the American colonies use clay plaster in the interior of their homes: "Interior plaster in clay and even antedated building frame houses, and should be visible on the inside of the filling fillets of the earliest skeletal houses where... waincot is not spoiled. continuing its use long after adoption of lath and refilling bricks for frames. "Where lime is not available or easily accessible, rationed or replaced with other binders. In Martin Weaver's seminal work he says, "Mud plaster consists of clay or soil mixed with water to provide" plastic "or a workable consistency.If the clay mixture is too plastic it will shrink, crack and distort drying. of the wall, fine sand and gravel are added to reduce the concentration of fine clay particles that cause excessive shrinkage. "Straw or grass is added sometimes with the addition of dirt.
In the earliest European settlers' plaster, mud plaster was used or more typically a lime-slurry mixture. In Harley McKee's book about the early American masons he wrote, around the year 1675 Massachusetts the plaster-determined contract, "Whether for the batten and four-room siele of the house between the heads of the above beams with a lime and feathered coat on clay, also to fill the tip the saddle roof houses with their ricks and plaisters with clay 5. For lath and partition plaster house with clay and lime, and to fill, batten, and plaister them with lime and hairs other than; and for Siele and glue them with lime, also to fill, batten, and plaster the kitchen up to the wall plate on each side 6. Daniel Andrews said is to find lime, brick, clay, stone, hairy, along with labor and workers.... "New Haven colony record in 1641 mentioned clay and straw and lime and hair as well. In German homes in Pennsylvania, clay use persists. "
Old Economic Village is one of the German settlements. The early nineteenth-century utopian village of Ambridge, Pennsylvania today, uses clay plaster substrate exclusively in the framework of high architectural wooden bricks and frames from the Party Room, the Great House and other large and commercial buildings as well as in bricks, frames and logs of residence community members. The use of clay in the form of plaster and the laying of bricks appears to have become common practice at the time not only in rural economic development when the settlement was founded in 1824. Specification for development, "Locked guard house in Chesapeake and Ohio Canal, written around 1828 , requires a stone wall to be laid with clay mortar, except 3 inches outside the wall... which is a good and pointed cement chalk. "The choice of clay is due to its cheap price, but also its availability. In Economy, root warehouses dug beneath houses produce clay and sand (rocks), or nearby Ohio rivers produce sand that is washed from sand rods; and lime cassava and oyster shells for lime furnaces. Other necessary building materials are also locally sourced.
The forest around the new village Economy provides straight grains, old oak trees for battens. The split bra hand begins with a log of straight-grained wood with the required length. The log is split into a quarter and then smaller and smaller bolts with sliced ​​and sled. When small enough, a froe and a hammer are used to separate the narrow pieces of batten - can not be achieved with field trees and many of their limbs. Livestock animals grazed in fields cut down by trees provide hair and manure to coat the plaster. Wheat fields and grains provide straw and other grass for clay plaster binders. But there is no uniformity in the recipe of clay plaster.
Straw or grass is added occasionally with the addition of fertilizer providing fiber for tensile strength as well as protein adhesives. Protein in the dirt acts as a binder. The hydrogen bond of the protein must remain dry to remain strong, so that the plaster of the mud should remain dry. With a ground wood frame structure, ground plaster is used on interior walls and ceilings as well as exterior walls as cavity walls and exterior coatings that isolate clay plaster from moisture penetration. The application of clay plaster in a brick structure risked the penetration of water from a failed mortar connection on the exterior brick wall. At Economy Village, the back and center walls of the brick-walled walls are laid in clay and mortar sand with the front, laid out in lime and mortar sand to provide weather proof seals to protect against water penetration. This allows rendering of clay plaster and installing a thin layer of lime and fine sand in exterior walled rooms.
Split battens are nailed with square pieces of nail battens, one to each member of the framing. With the hand split lining the plaster has the luxury of making battens to fit the cavity attached. Length of two to six feet is not uncommon in Economic Village. Hand split lath is not uniform as sawn. The straightness or elasticity of the grain affects the thickness or width of each battens, and thus the distance of the battens. Rough layers of clay vary to cover irregular battens. Window and door trim as well as mudboard (pedestal) acts as a screed. With variations in batten thickness and use of rough straw and manure, clay layer of thick plaster compared with lime and plaster of gypsum. At Economy Village, the top layer of chalk is a thinner veneer often inch or less that proves the scarcity of limestone supply there.
Plaster clay with a lack of tensile strength and press is not preferred because industrial mining and technological advances in kiln production lead to the exclusive use of lime and then gypsum in plaster applications. However, clay plaster is still there after hundreds of years of sticking to separate the battens on rusty rusty nails. Wall variations and roughness reveal hand-made and textured fun alternatives to complete modern machine-made substrates. But the plaster layer of clay is rare and quickly passes. According to Martin Weaver, "Many interiors of historic buildings in North America... too often... one of the first things missing in the bustle of interior demolition which unfortunately became a common escort for" heritage preservation "in the guise of rehabilitation development."
Gypsum plaster
The plaster of gypsum, or Paris plaster , is produced by heating gypsum to about 300 ° F (150 ° C):
When dry plaster powder is mixed with water, it re-forms the gypsum. Unmodified plaster setting begins about 10 minutes after mixing and finishes in about 45 minutes; but not fully set for 72 hours. If plaster or gypsum is heated above 266 ° F (130 ° C), the hemihydrate is formed, which will also be re-formed as gypsum when mixed with water.
At warming up to 180 ° C, the almost water-free form, is called? -anhydrite (CaSO 4 ), where n = 0 to 0.05 ) is generated. ? -Anhidrite reacts slowly with water to return to a state of dihydrate, a property that is exploited in some commercial desiccants. On heating above 250 Â ° C, the so-called anhydrous form completely? -anhidrit or a burning plaster is formed.
The large gypsum deposit at Montmartre in Paris produces a "calcined cast" (gypsum gypsum or gypsum) commonly known as "Paris plaster."
Plasterers often use gypsum to simulate the appearance of wood, stone, or metal surfaces, on film and theater sets for example. Currently, theater plasterers often use expanded polystyrene, although the job title remains unchanged.
Paris plaster can be used to impregnate the gauze bandages to make sculptures called plaster plaster. It is used similarly to clay, as it is easily formed when wet, but becomes a formidable and lightweight structure. It is a material (and sometimes still) used to make classical orthopedic cast to protect limbs with broken bones, artistic use has been partially inspired by medical use (see orthopedic cast). The Modroc Set is an early example of a composite material. The hydration of the Paris plaster depends on the reaction of water with dehydrated or partially hydrated calcium sulfate present in the cast.
Lime plaster
Lime plaster is a mixture of calcium hydroxide and sand (or other inert fillers). Carbon dioxide in the atmosphere causes plaster to regulate by converting calcium hydroxide into calcium carbonate (limestone). Whitewash is based on the same chemistry.
To make lime lime, limestone (calcium carbonate) is heated above about 850 ° C to produce lime (calcium oxide). Water is then added to produce dead lime (calcium hydroxide), which is sold as wet or white powder putty. Additional water is added to form paste before use. Pasta can be stored in an airtight container. When exposed to the atmosphere, calcium hydroxide very slowly turns back into calcium carbonate by reaction with atmospheric carbon dioxide, which causes the plaster to increase its strength.
Lime plaster is a common building material for the inner wall surface of a process known as batten and plaster, where a series of wood strips on studwork frames are covered with semi-arid casts that harden to the surface. Plaster used in most lath and plaster construction especially lime plaster, with healing time of about one month. To stabilize the lime plaster during the drying process, a small amount of the Paris plaster is inserted into the mixture. Because of the rapid Paris plaster, "retardants" are used to slow the timing of sufficient time to allow workers to mix large quantities of lime plaster. The modern form of this method uses a metal net extending over a wood or metal structure, allowing great design freedom as it can be adapted to simple and plural curves. Currently this building method has been partially replaced with drywall, also mostly consisting of plaster gypsum. In both of these methods, the main advantage of this material is that it is resistant to indoor fire and thus can help reduce or eliminate structural damage or destruction if the fire is extinguished immediately.
Lime plaster is used for frescoes, where the pigment, diluted in water, is applied to the still-wet plaster.
The US and Iran are the major casts producers in the world.
Cement plaster
The cement plaster is a mixture of plaster, sand, portland cement and suitable water which is usually applied to the interior and exterior of the brick to achieve a smooth surface. The interior surface sometimes receives a final layer of plaster gypsum. The walls built with stock bricks are usually plastered while the facial brick walls are not plastered. Various cement based plasters are also used as proprietary spray fire products. It usually uses vermiculite as a mild aggregate. Heavy versions of such plaster are also used for fireproofing exteriors, to protect LPG ships, pipe bridges and boat skirts.
The cement plaster was first introduced in America around 1909 and is often called by the generic name stucco after the leading manufacturer at the time. The advantages of the cement plaster recorded at the time were force, hardness, fast adjustment time and durability.
Heat resistant Plaster
Heat resistant plaster is a building material used to coat the walls and breast chimney. The goal is to replace conventional gypsum in cases where the temperature can be too high for gypsum plaster to stay on the wall. The heat-resistant plaster shall be used in cases where the wall tends to exceed the temperature of 50 Ã, Â ° C.
Maps Plaster
Usage
Architecture
The plaster can also be used to create intricate detail for use in the interior of the room. It may be geometric (simulating wood or stone) or naturalistic (leaf simulation, vines, and flowers). It is also often used to simulate wood or stone details found in larger buildings.
In modern times this material is also used for False Ceilings. In this case, the powder form is converted in sheets and the sheets are then affixed to the base ceiling with the help of fasteners. This is done in a variety of designs that contain various combinations of lights and colors. The general use of this plaster can be seen in the construction of the house. After development, direct painting is possible (the French do it), but elsewhere the plaster is used. The walls are painted with plaster which (in some countries) is nothing more than calcium carbonate. After drying the plaster the calcium carbonate turns white and then the wall is ready to be painted. Elsewhere in the world, like England, a smoother plaster layer is added on the plasterboard (or sometimes a brick wall directly) to give a fine texture of a polished brown ready for painting.
Art
Many of Europe's largest mural paintings, such as the Sistine Chapel ceiling in Michelangelo, are executed in fresco, meaning they are painted on a thin layer of wet plaster, called intonaco; the pigments enter this layer so that the plaster itself becomes the medium that holds it, which contributes to the perfect resistance of the fresco. Additional work can be added secco over a dry cast, although this is generally less durable.
Plaster (often called plastering in this context) is a much easier material for making relief than stone or wood, and is widely used for the relief of large interior walls in Egypt and the Near East from ancient times to Islamic times (more recently for architectural decoration , as in Alhambra), Rome, and Europe from at least the Renaissance, as well as elsewhere possible. However, it needs excellent conditions for long-lasting in unkempt buildings - the Roman decorative plaster is mainly known from Pompeii and other sites buried by ashes from Mount Vesuvius.
The plaster can be cast directly to the wet clay mold. In creating these prints (prints designed to make multiple copies) or waste molds (for single use) will be made of plaster. This "negative" image, if properly designed, can be used to produce clay production, which when fired in a kiln becomes a terra cotta building decoration, or it can be used to make concrete statues. If this desired positive plaster will be built or discarded to form a durable artwork. As a model for this stone carver will be enough. If intended to produce bronze casting, positive plaster can be further worked out to produce a smooth surface. The advantage of this plaster image is relatively cheap; should a patron approve a durable image and be willing to bear further costs, subsequent prints can be made for the creation of wax drawings for use in lost wax casting, a much more expensive process. In lieu of producing bronze images suitable for outdoor use, plaster drawings can be painted to resemble a metal image; Such sculptures are only suitable for presentations in weather-protected environments.
Plaster expands while hardened then contracts a little before it actually hardened. It makes excellent plaster for use in molds, and is often used as an artistic material for casting. Plaster is also usually spread in armatur (shape), made of wire, cloth, or other materials; a process for adding upgraded details. For this process, plaster or acrylic-based plaster can be used, known as plastering.
The product consists mainly of plaster of Paris and a small amount of Portland cement is used for casting sculptures and other art objects as well as prints. Much harder and stronger than Paris's straight plaster, these products are only for indoor use because they are rapidly degraded in the rain.
Funeral process
The plaster is used by many mortis and funeral home directors to recreate the destroyed tissue, reconnect the broken limbs into dead bodies, and fill up the wounds suffered during an accident or murder that causes death.
Medicine
Plaster is widely used as support for broken bones; a bandage impregnated with a dampened tape and then wrapped around a damaged limb, inserted into an easily removable but easily disposed tube known as an orthopedic cast.
Plaster is also used in the preparation of radiotherapy when creating individual immobilized shells for patients. Plaster plaster is used to build the head and neck impression of the patient, and the liquid plaster is used to fill the impression and produce plaster breasts. Transparent polymethyl methacrylate material (Plexiglas, Perspex) then vacuum formed on top of this breast to create a clear face mask that will hold the patient's head firmly when radiation is being sent.
In dentistry, plaster is used to install a casts or tissue model of the mouth. This diagnostic and working model is usually made of gear, a stronger, harder and denser plaster derivative made from gypsum under pressure. The plaster is also used for investing and denture wax flasks, wax which is then removed by "burning," and replaced with denture base ingredients. The denture base is usually acrylic then heals in plaster investment mold. Plaster investments can withstand the heat and high pressure required to ensure a rigid denture base. In addition, in dentistry there are 5 types of gypsum products depending on consistency and usage: 1) plaster impression (type 1), 2) plaster model (type 2), gear (type 3, 4 and 5)
In orthotics and prosthetics, plaster plasters are traditionally used to create the impression of a patient's limb (or residue). This negative impression then, itself, is filled with plaster of Paris, to create positive limb models and be used in the final medial device fabrication.
In addition, dentures (false teeth) are made by first taking the impression of a tooth using a soft, delicate material that can be removed from around the teeth and gums without losing loyalty and using the impression to create a model of wax and gum. This model is used to make plaster molds (which are heated so that the wax melts and flows out) and the denture material is injected into the mold. After the curing period, the mold is opened and the dentures are cleaned and polished.
Fire protection
Plaster has been used in passive fire protection, as a fire-resistant product, for decades.
The finished plaster releases moisture when exposed to fire, acting to slow the spread of fire, for an hour or two depending on the thickness. It also provides some isolation to slow the flow of heat into structural steel elements, which otherwise would lose its power and fall in fire. Early versions of this plaster have used asbestos fibers, which have now been banned in industrialized countries and have led to significant removal and re-coating. More modern plasters fall into the following categories:
- fibrous (including mineral wool and glass fiber)
- a mixture of cement with mineral wool or with vermiculite
- plaster gypsum, leavened with polystyrene granules, and chemical expansion agents to reduce the density of finished products
One distinguishes between interior and exterior fireproofing. Interior products are usually less substantial, with lower density and lower cost. Exterior products must be more extreme fireproof and other environmental conditions. Exterior products also tend to be more attractive, while their interior cousins ​​are usually just sprayed in place. Rough surfaces are usually forgiven in the building because the ceiling that goes down often hides it. Plaster exterior fireproofing loses ground for more expensive intumescent and endothermic products, based only on technical merit. Trade jurisdictions at union construction sites in North America remain with plaster, regardless of whether the plaster is decorative or used in passive fire protection. Plaster-based cement and gypsum tend to be endothermic. The fireproof plaster is closely related to firestop mortar. Most firestop mortars can be sprayed and fitted very well, due to the fine detail work required from firestopping, which directs their mix designers to utilize concrete mixing, allowing easier tooling than ordinary mortars.
3D Printing
The powder powder and the inkjet 3D print head are generally based on the plaster gypsum reaction with water, where water is selectively applied by the inkjet head.
Security issues
The chemical reaction that occurs when plaster is mixed with water is exothermic. When the plaster set, it can reach temperatures over 60 Ã, Â ° C and, in large volumes, can burn the skin. In January 2007, a high school student in Lincolnshire, England suffered third-degree burns after wrapping his hands in a cast bucket as part of a school art project. The wound was so bad that he had to cut both his thumb and six fingers.
Some variations of plaster containing silica or asbestos powder may pose a health hazard if inhaled. Asbestos is an irritant that is known when inhaled and can cause cancer, especially in people who smoke, and inhalation can also cause asbestosis. Inhaled silica can cause silicosis and (in very rare cases) can promote cancer progression. Persons who work regularly with plaster containing these additives should take precautions to avoid inhaling powdered powder, healed or not cured. (Note that asbestos is rarely used in modern plaster formulations because of its carcinogenic effects.)
One can be exposed to Paris plaster at work by inhaling, swallowing, skin contact, and eye contact. The Occupational Safety and Health Administration (OSHA) has established a legal limit (allowable exposure limits) for Paris exposure plaster at work as a total exposure of 15 mg/m 3 and 5 mg/m 3 breathing exposure for 8 hours. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 10 mg/m 3 total exposure and 5 mg/m 3 more respiratory exposure of 8 working hours. 
See also
References
External links
Source of the article : Wikipedia
0 Comments