The main object of applying distemper to the plastered surfaces is to create a smooth surface. The distempers are available in the market under different trade names. They are cheaper than paints and varnishes and they a present a neat appearance. They are available in a variety of colours.
Properties of distempers: Following are the properties of distempers:
(1) On drying, the film of distemper shrinks. Hence it leads to cracking and flaking, if the surface to receive distemper is weak.
(2) The coatings of distemper are usually thick and they are more brittle than other types of water paints.
(3) The film developed by distemper is porous in character and it allows water vapour to pass through it. Hence it permits new walls to dry out without damaging the distemper film.
(4) They are generally light I colour and they provide a good reflective coating.
(5) They are less durable than oil paints.
(6) They are treated as water paints and they are easy to apply.
(7) They can be applied on brickwork, cement plastered surface, lime plastered surface, insulating boards, etc.
(8) They exhibit poor workability.
(9) They prove to be unsatisfactory n damp locations such as kitchen, bathroom, etc.
Ingredients of a distemper: A distemper is composed of base, carrier, colouring pigments and size. For base, the whiting or chalk is used and for carrier, the water is used. Thus it is more or less a paint in which whiting or chalk is used as base instead of whit lead and the water is used as carrier instead of linseed oil.
The distempers are available I powder form or paste form. They are to be mixed with hot water before use. The oil-bound distempers are a variety of an oil paint in which the drying oil is so treated that it mixes with water. The emulsifying agent which is commonly used is glue or casein. As the water dries, the oil makes a hard surface which is washable.
It should be remembered that most of the manufacturers of ready made distempers supply completely directions for use of their products. These directions are to be strictly followed to achieve good results.
Process of distempering: The application of distemper is carried out in the following way:
(1) Preparation of surface: The surface to receive the distemper is thoroughly rubbed and cl
The fresh lime is slaked at site of work and mixed thoroughly with sufficient quantity of water in a tub. It is then screened through a clean cloth. The clan gum dissolved in hot water is then added at the rate of 20 N per m3 of lime. The rice may be used in place of gum.
The surface to be whitewashed should be cleaned before the work is started. For whitewashing walls which are whitewashed before, the old loose whitewash is to be first removed and repairing to the plaster is carried out, if necessary.
The lime is toxic for germs. It reflects light and thus it increases the brightness of the surface. The whitewashing therefore is extensively used for interior wall surfaces and ceilings of houses.
The pr0ocess of whitewashing is sometimes used for exterior wall surfaces also. A satisfactory work gives an opaque smooth surface with uniform white colour and does not readily come off on the hand, when rubbed.
This is prepared by adding the colouring pigment to the screened whitewash. It should be seen that the colouring pigment is not affected by the presence of lime. Ordinarily, the yellow earth is popular of colourwahsing. Generally, the walls are colourwashed and ceilings are whitewashed. The mixture is to be kept constantly stirred during use.
The colourwash is applied in the same fashion as the whitewash. A satisfactory work does not give out powder when the finished surface is rubbed with the fingers.
The process of colourwashing imparts cleanliness and pleasant appearance of the surfaces which are treated.