Plastering - Using Different Types of Plaster on WallsPlasters used for building construction come in three main types: gypsum plaster (POP), lime plaster and cement plaster. Apart from building and medicine, plasters can also be used for drawing where it can serve as medium for the painting and in production of marbles.
Plastering buildings have been upgraded over the years but was well documented and popularised during Victorian era. Prior to the use of plasters for decoration, they were mainly used as part of construction where cracks and holes on the walls are covered to avoid insects and other animals from inhabiting such cracks. Clay from soft sand have been used for centuries to plaster and beautify walls in Africa, Asia, North America especially amongst Indian and in other places. There is no state proportion of mixture for plastering materials, but standard procedures should be observed, therefore experts' advice should be sort prior to carrying out plastering of your building.
Plastering with Gypsum
The use of gypsum for plaster work has really revolutionised interior decoration of buildings. This material also known as Plaster of Paris because of its large deposit at Montmartre in Paris is used for intricate design of columns and ceilings, it is not a weight carrying structure and is confined only to decorations. It is a dry powder that when mixed in water will readily harden but unlike cement and mortar, its shape can be changed or modified with the use of sculpture tools and sandpaper. Conventional method for roofing and ceiling buildings is gradually shifting towards the use of POP for obvious reasons; Shapes and sizes can be fabricated to fit desired taste and fashion. It is fire-resistant and this reduces the incidence of fire outbreak. It is light and therefore can be used on soft materials like woods, plastics etc.
Gypsum Plastering Procedure
- Design mould in wooden, metal or plastic structure of your required shape and size
- Obtain pure gypsum. They come in various packs between 5kg to 50kg
- Mix thoroughly and add appropriate quantity of the gypsum with water. It should not be watery but in molten form
- Transfer the mixed gypsum to mould and allowed to set for few minutes. In some cases, it is allowed to dry out.
- Remove from mould and transfer directly to the sit to be decorated and attach to wall or ceiling firmly to the desired position with the help of the plaster and allowed to set for drying.
- Finish the mould with sandpaper or file to desired modification, spray with colour if need be. Spraying with machine give the best quality.
Plastering with Lime
This is a chemical mixture of Calcium Hydroxide and sand. When exposed to the atmosphere, Carbon dioxide in the air causes setting of the plaster and thus transforms the Calcium Hydroxide to Calcium Carbonate (limestone).
Lime Plastering Procedure
- The limestone is heated and quicklime is produced
- Add water to produce slaked lime. Continue to add water till paste is formed
- Transfer paste into air-tight container to avoid air which will reverse the paste back to limestone with subsequent drying
- Pigment (desired colour) diluted in water is mixed into the paste
- Apply paste to desired portions, design with bare hands, or use prepared mould to give perfect shape
The most popular type of cement is the Portland cement, and it is very suitable for plastering walls, for decoration of interiors and exteriors, but the most important use of Portland cement is:
- For laying blocks and bricks (masonry)
- Plastering walls in order to smoothen walls
- Building of concrete walls, floors and lintels (in various mixtures of sand, gravels, stones etc.)
- For holding marbles on walls and floors, with or without mixture of any additives like sand
Cement has very high insulating properties against heat and electricity. It is also fire proof and confers additional strength to steel. Cement takes time to set when used for plastering and this makes it less useful for designing intricate moulds for decoration. Also, due to its weight (heavy), very large chunk can not be applied at a time.
There are very many methods to go about this because there are lots of different plastering techniques for cement.
- For simple walls without designs and decorations, cement can be mixed with sand or silicon
- For laying of marbles on floor and walls, cement can be mixed with gypsum, or limestone or both.
- For use in ponds, swimming pools and water logged areas, only cement should be used
- For rough wall surface, large proportion of sand are mixed with cement.
All the mixture are done with water
Cement Plastering Procedure
- Approximate and measure the quality of cement to be used
- Mix with water till paste is formed (should not be watery so that it does not fall off the wall or shift towards gravity)
- Roughen smooth surface with hammer or chisel
- Sprinkle surface with water with the aid of a sponge of sprinkler
- With the aid of trowel apply the mixed cement on the wall surface, allow to set for a while and smoothen with trowel
- Apply design if need be when still soft and wet because when dry it is very strong
Cement Plastering Tools
- Trowel for plastering
- Shovel or spade for mixing
- Head pan or bowl
- Measuring tape
Cement Plastering Warnings
- Do not mix cement with or touch wet cement with bare hands because it reacts exothermically with water. This could lead to severe burns.
- When opening sack containing cement, use face mask to avoid inhalation of cement as this could cause various degrees of cancer as well as asthma.
- When mixing cement, do so under shade as it might dry up before applying it to the walls.
- Don't apply plasters on walls during frosty weather because cold weather slows hardening of plaster.
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