Plaster of Paris, uses, pros & consArticles > Plaster of Paris, uses, pros & cons
The Plaster of Paris is also called Parisian-plaster. The Paris-Plaster is made up of a quick set hemihydrate Calcium Sulfate (gypsum). Calcium Sulfate and water are known as Gypsum. Gypsum is a naturally occurring metamorphic rock, which is found in almost every country in the world. Calcium Sulfate naturally contains water in it. The presence of water in gypsum gives it a softening and cooling effect, which is why gypsum-stone caves provide a cooling effect in the summer season. Calcium Sulfate is a fine powder ground with the help of heat and grinder to obtain the Paris Plaster. The plaster of Paris when soaked with water, it hardens, when it is allowed to dry. It hardens like a soft stone. The Plaster of Paris is used to build finishes of the desired shape, with the help of adding straw and fiber reinforcement to it. It is known as the Plaster of Paris, because of its abundantly (gypsum) quarrying near Paris. It is widely used in interior design and decoration. It has many advantages that make it very suitable and eligible for interior decoration work. The Plaster of Paris is recommended for many reasons, such as its easy manageability, smoothness, and light finish due to the attractive appearance of the gypsum itself, it does not shrink and thus does not allow crakes in the structure, readily build the desired shape, and so on. There is, however, there are demerits of Parisian-Plaster, which hinders its use in external finishing, such as being slowly soluble in water. It will not be used with plaster instead of OPC cement and lime cement, as it is more expensive. It is not recommended because it requires more skilled workers, thus increasing labor costs. However, the cases of use of the Paris Plaster are as follows:
Use of Paris Plaster:
There are dozens of uses of the plaster of Paris in civil engineering and architecture, however, the most common uses of it are as follows:
• The Plaster of Paris does not tend to shrink and does not create cracks in the surface when it dries. Therefore, a structure made of plaster-de-Paris does not degrade when dried. The initial state and structure remain the same until the end.
• The Plaster of Paris is used to make the best molding for its espreading quality and because of it does not loosen its shape and form.
• Used to pre-cast and manage parts of decorative plasterwork on the roof and corner of rooms.
• Used to make mould for rejoining broken bones. Unmobilizing broken bones will soon heal.
• Sculptors while working on sculptures work directly on the Paris plaster, as it is easy to design and build a structure.
• Gesso is made of Paris plaster mixed with glue and is used to apply on wood panels, concrete, stone, or fabric before providing an oil-based paint.
• Used to make toys, toys, cheap ornaments, cosmetics, blackboard, chalk, and photo.
• Used in a chemistry laboratory to close air gaps in apparatus where air conditioning is required.
• It is used to smooth the surface of the walls of the house before painting and making decorative designs on the roofs of houses and other buildings. (see Plaster in the construction of decorative buildings).
Pros of Plaster of Paris:
- It is light-weighted but more durable.
- It protects the heat conduction into the structure as it has thermal conductivity.
- Plaster of Paris is resistant to fire and used as a heat insulator.
- Plaster of Paris does not shrink on hardening, therefore, it does not allow crakes to develop in the structure.
- It knocks resistant as it forms a thick surface.
- It mixes well with water, therefore, it can easily be spread and leveled.
- It has good adhesion with fibrous material.
- Color can be easily settled on it, as it gives a firm surface.
- It does not show any chemical action on paint, therefore, painting on the surfaces made of plaster of Paris are well appreciated.
- The gypsum content provides a good shine and smoothness to the decorative interior finishing. This is the reason for which interior decorative ceilings and cornice are constructed with plaster of Paris.
- Molding the plaster of Paris to any shape is quite easy.
Disadvantages of Plaster of Paris:
- As it is slightly soluble in water, therefore, it is not recommended in exterior use.
- It is expensive than ordinary cement and lime cement.
- In moist condition, the use of the Plaster of Paris is not suitable.
- Labor costs go very high, as the skilled labor is required to set the finishing by plaster of Paris.
Preparation of Plaster of Paris:
It is prepared by heating gypsum (calcium sulfate dehydrate) up to 140 -180 °C or 248–356 °F. Plaster of Paris is obtained in the form of a fine-grained white power, with half quantity of the water as in the gypsum. Plaster of Paris is scientifically known as Calcium Sulfate Hemihydrate. Hemihydrate means the haploid quantity of water as compared to that of solid gypsum.
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