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Friday, April 29, 2022

GUIDELINES OF HOME PAINTING | GENERAL CONSIDERATIONS IN-HOME PAINTING | HOMESLIBRO

GENERAL CONSIDERATIONS IN-HOME PAINTING

 

Paints can be classified into "breathing and non-breathing" types depending on their ability to let moisture pass through the painted surfaces. Oil-based paints leave an impermeable film on the surface after drying. Hence if moisture is entrapped behind the film, the surface blisters. This is the non-breathing type of paint. Cement paint after drying allows moisture to pass through the painted surface. They are the breathing type of paints. In places where moisture tends to accumulate in RC slabs (under bathrooms and wet areas of upper floors), it is preferable to use the breathing type of paints. Before we go into the details of these works, we should remember the following general precautions to be taken.


1. Cement paint has to be applied to wet surfaces. Limewash and colour wash can also be applied to wet surfaces, but other superior paints such as OBD and plastic emulsion paints should be applied only after the moisture in the walls has dried out. In the case of new walls, these special paints can be applied only about six months after plastering has been completed and the moisture in the wall has completely dried out. (In many cases, cement paint is given initially and after a period of time, the final superior paint is applied.)

 

2. New surfaces should be given at least three coatings of paint. The first coat is the pruning coat with a suitable primer. There are different primers for wood, plaster and metal. The second coat, called the undercoat, covers the primer coat and acts as a bond to subsequent coats. In many cases, it is only a thinned paint of the finishing coat. The third coat is the final finishing coat. The final finish can be as follows in order of smoothness:

(a)    Mat finish or flat finish

(b)    Eggshell

(c)    Oil gloss

(d)    High gloss such as enamel

However, a high gloss finish will highlight the irregularity of the surface and are generally not preferred except in high-class works.

 

3. When painting outside walls, it is advisable to paint, if possible, the surfaces which are on the shady side of the building so that the direct rays of the sun are avoided.

 

How to prepare newly plastered walls for painting?

Preparation of Newly Plastered Walls for Painting

After the wall has dried and matured for a few months, we first apply a coat of cement primer (white). Irregularities of the surfaces should be then rectified by putty before painting is started. For example, in ordinary house construction, we can use plaster of Paris as putty. For superior work as in showrooms, special copolymer emulsion putty, suitable for exterior and interior, containing the primer coat is also available in the market. They are, however, costly. (It is more convenient to first apply white primer on cement plastered walls before applying putty. The white background will show up the irregularities and the putty can be applied more effectively. This procedure will also reduce the amount of putty required.) Rub putty with sandpaper to smoothen the surface. Apply one more coat of primer and allow it to dry for 10 to 12 hours before applying the chosen paint as an undercoat. The following points are important:

 

1. Oil and acrylic paints and distempers do not fare well if there is alkalinity in the surface to be plaster or if the wall has been previously whitewashed with lime. Hence it is essential to apply alkali-resistant cement primer on these whitewashed surfaces before applying these paints.

 

2. When painting exterior walls all moulds, algae, moss, etc. should be removed by scraping. The organic growth can be arrested by an ammoniacal copper solution containing 7 gm of copper carbonate dissolved in 80 cc of liquid ammonia diluted in one litre of water. Alternately 2.5% magnesium silicon fluoride solution may be used. When cleaning with these solutions, the surface should be allowed to dry before painting. Special exterior paints are more long-lasting than normal paints. They also resist the growth of algae and fungus.

 

3. Where efflorescence is seen in brick walls, water should not be used to wash out the efflorescence. If water is used, the salt may be absorbed back into the pores and will be precipitated again when it dries out. The deposit should be brushed and cleaned in the dry state itself.

 

Types of Primer Coat

The primer paints to be used for various building works is given in Table below.

S.NO

SURFACE

TYPES OF PRIMER

1

Hard and soft work

Pink wood primer (IS 3536) Aluminium

2

Resinous and plywood

primer (IS 3585) Zinc chromate primer

3

(a) Aluminium and light alloys

(IS 104) Red oxide zinc chromate primer

(b) Iron, steel and GI

(IS 2074)

4

Cement concrete, plastered surface, asbestos

Cement primer (IS 109) (white)

(The covering capacity of these primers is 18 to 20 m2 per litre per coat.)

 

What are the types of paints to be used?

Types of Paints to be Used

The approximate breakdown of the present consumption of paints in urban buildings is reported as follows.

Synthetic enamel

56%

Distemper

22%

Cement paint

17%

Acrylic emulsion paint

5%

 

Emulsion paints are the costliest of all these paints.

Exterior paints. As labour costs are increasing and as a painting urban high rise buildings are cumbersome, there is a trend to go in for long life exterior paints, especially in high rise flats and office buildings. As the exterior painting of high rise buildings has become very important, special exterior paints (100% acrylic emulsion based paints and also cement paints) are now used more and more. Many paint manufacturers especially advertise their exterior paints.

Choosing paint. In rural housing which forms more than 65% of the homes in India, the low cost., colour wash distemper and cement paints are quite popular. The possible alternatives are discussed further.

 

1. Painting of interior plastered brickwork. We can use whitewashing, colour washing, cement paint, dry distemper, oil bound distemper, plastic emulsion paint or enamel interior paint depending on our affordability.

 

2. Painting of exterior plastered brickwork. We can use whitewashing, colour washing, special waterproof cement paint, or special exterior acrylic paints. (Distempers are not used for exterior surfaces.)

 

3. Painting of plastered concrete surfaces. (Same as plastered surfaces above)

 

4. Painting of metal surfaces. Pretreatment with metal primer (red oxide or zinc chromate primer) and exterior enamel paint for exterior surfaces and interior enamel paint for interior surfaces.

 

5. Painting of woodwork. Good wood in which we want the grains to be seen is not painted but varnished. If we want to expose the gains as in furniture, we first rub it down to expose the grains, then apply a sealer coat and finally clear the varnish. We can also stain the wood with wood stains before we apply varnish. If we want to paint wood with opaque paints, pink wood primer is applied first and the wood can be painted with oil, synthetic enamel or plastic emulsion paints.

 

6. Painting AC sheets and boards. We apply two coats of alkali-resistant primer and then acrylic paints or synthetic enamel flat paints.

 

7. Painting GI sheets. We apply a priming coat of red oxide or zinc chromate paint followed by synthetic enamel paint. (New GI sheets should not be painted till they have weathered for about a year in contact with the atmosphere and the protective oxides are formed on the surface.)

Must Read: Types of Paint Used in Construction and Its Uses


How to choose wall colours?

Choosing Colours

Colours have a positive effect on our mood and emotions. The choice of colour should also depend on the size of the room. Colours that might look good in a large auditorium foyer will look gaudy in a small flat. Colours can create an optical illusion of increasing or decreasing the size of a room.

 

A ceiling painted white seems higher than a ceiling coated darker than the walls. When choosing colours for not very well lighted rooms as in blocks of flats, the colour should be chosen with respect to the effect of sunlight and the effect of artificial light during nights.

 

The reflective values of colours vary from 70 to 90% in white to only 10 to 20% for deep colours. In any case, light colours are always safe in residences and give good reflective surfaces. There are more than a hundred shades of paints on the market to choose from.


Must read: Types of Paint Used in Construction and Its Uses

Must read: How to do whitewashing and colour washing

Must read: How to Do Painting With Cement Paint

Must read: How to Do Painting With Dry Distemper

Must read: How to do painting of plastered walls with plastic emulsion paint

Must read: How to do painting iron and steel with enamel paints?

Must read: How to do painting new / old woodwork with synthetic enamel paint

Must read: How to do polishing wood which has attractive grains?

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