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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