PAINTS AND VARNISHES
PAINT
• Paint is a mixture of
liquid or medium and a
coloring or pigment to
impart color and provide
protective coating to
the surface.
• Paints are used to
protect metals, timber
or plastered surfaces
from the corrosive
effects of weather, heat,
moisture or gases etc.
and also to improve
their appearance.
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COMPONENTS OF PAINTS
Base
Extender
Binders/ Vehicle
Thinner
Colouring
Pigment
Dryer
Additive
COMPONENTS OF PAINTS
Base
- Is one of the main components of paint and is
commonly referred to as the body of the paint.
Example of Base
White Lead
Red Lead
COMPONENTS OF PAINTS
Example of Base
Zinc Oxide
Titanium White
COMPONENTS OF PAINTS
Example of Base
Iron Oxide
COMPONENTS OF PAINTS
Extender
The extender also referred to as the
filler
The filler is added to the paints to
increase or extend the volume of the
paint without disturbing other
essential properties
COMPONENTS OF PAINTS
Example of Extender or Filler
Barite
Gypsum
Chalk
Silica and Magnesium Silicates
COMPONENTS OF PAINTS
Binders or Vehicle
The vehicle is basically composed of an oily liquid in
which both the base and the pigment are soluble.
Some Example are:
Fish Oil Linseed Oil
Bleached Oil
Dehydrated Castor Oil
COMPONENTS OF PAINTS
Thinner
Also called a solvent.
It is added to the paints with the objective of making
the application of the paint easy, uniform and
smooth.
Spirits Petroleum
Turpentine Coal Tar and other Hydrocarbons
COMPONENTS OF PAINTS
Colouring Pigment
The pigment is the responsible for imparting the
color of the paint.
The most common types of pigment used are zinc
oxide and titanium oxide.
COMPONENTS OF PAINTS
Dryer
The dryer is usually added to the paint to accelerate
the drying of the vehicle of the paint.
Some common examples of the dryer are organic
salts of lead, iron, zinc, calcium, etc.
COMPONENTS OF PAINTS
Additive
The additive is added in a small amount to the paint.
It is added to the paints to improve the properties of
paint such as opacity, colour, dispersion of pigment,
anti-freezing properties, corrosion-resistant
properties, etc.
Functions of Paint
Paint performs following functions :
It protects wood from decaying.
It prevents corrosion of metals.
It renders surface hygienically safe and clean.
It gives decorative and attractive appearance
to the surface.
It also protects the surface from harmful
effects of atmospheric agencies.
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Manufacture of Oil Paints
The base (white lead) is thoroughly ground in
oil
Thinner (turpentine oil) is mixed to give it
necessary workability
Pigment and drier are separately ground in
linseed oil and mixed with turpentine oil to
make it thin
Pigment mixture intimately mixed with
already prepared base
Prepared paint is strained through fine cloth
or sieve.
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TYPES OF PAINT
1. Oil Paint: ordinary paint.
2. Bituminous paint: prepared by dissolving asphalt
or bitumen in oil or petroleum.
3. Cement paint: It consists of cement and hydrated
lime mixed along with a coloring pigment.
4. Colloidal paint: a paint with no inert material.
5. Aluminum paint: aluminum powder suspended
in spirit varnish or oil varnish.
6. Asbestos paint: peculiar type, applied to places
exposed acidic gases and steam.
7. Cellulose paint: prepared from nitro cotton
celluloid sheets.
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TYPES OF PAINT
8. Emulsion paint: It consists of polyvinyl acetate
and synthetic resin as binding material
9. Enamel paint: It consists of white lead ground in
small quantity of oil and mixed with petroleum spirit
and resinous matter.
10. Graphite paint: black in color, applied on iron
surfaces.
11. Luminous paint: contains calcium sulphide with
varnish.
12. Silicate paint: prepared by mixing calcined
ground silica with resinous substances
13. Anti-corrosive paint: consists of oil and strong
drier.
14. Plastic paint: variety of plastic present, applied
using brush or spray painting.
15. Synthetic rubber paint: prepared from resin.
PAINTING PROCESSES
o Application of paint to a surface either with a
brush or by spraying is known as painting.
o The surface to be painted should be perfectly
smooth, clean and dry.
o Presence of moisture between the paint and
surface to be painted or between successive
coats of paints causes blisters.
o The paint is applied on the surface in two, three
or four coats. The first coat is known as priming
coat and last one as finishing coat.
PAINTING ON PLASTERED
SURFACE
o A plastered surface should be painted only after it has
thoroughly dried, otherwise the paint would get sploit.
o As far as possible fresh plastered surfaces should not be
painted. At least 6 months to 12 months time should be
given to the plastered surface to dry completely.
PAINTING ON CONCRETE
SURFACES
o SURFACES
For painting concrete surfaces, cement paints
are used. They are available in powder form.
They are used by mixing with water.
o Prepared paint should be consumed within 2
hrs or its preparation.
o Two coats should be applied at an interval of 24
hrs. The painted surface should be cured by
sprinkling water at intervals.
Distemper
• Distemper is a kind of whitewash that
appears early in life cycle. Its is easily
mark as decorative paint. Its has been
used for painting walls and other sorts of
house décor since antiquity.
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Plastic Emulsion
Paint
• Is water base wall paint.
• It is base on acrylic and provide a smooth
matte finish to the walls.
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Plastic Emulsion
Paint
Latex Vinyl Emulsion
(Acrylic)Emulsion Paint
Paint
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Solvent or
Oil-Based Paints
Solvent-based paints contain organic compound as
solvents. The organic compounds ensure a hard
and durable finish that resist scratches and
abrasions on your wall.
Oil-based paint contains natural (linseed) or
synthetic (alkyd) oil as a base.
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Exterior Paints
Exposed to various weather condition.
It provide protection against moisture caused by rain,
snow and ultraviolet radiation caused by sunlight.
It also has to protect against fungal growth.
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Defects in Painting
Fading
The paint may lose some of its colour due to effects of sunrays
on colouring
pigments.
Flaking
Due to poor adhesion, paint may peel off from the surface.
Grinning
If the opacity of the final coat is insufficient, the back ground of
the painted surface is clearly visible. This defect is known as
grinning.
Bloom
Due to bad ventilation or defective paint, dull patches are
developed on the painted surface.
Flashing
This is opposite of bloom. In this defect, glossy patches are
developed on
the painted surface. The reason of this defect may be cheap
paint, weather
reaction or poor workmanship.
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Defects in Painting
Running
This defect occurs when the surface to be painted is very smooth.
In this defect, small areas of the surface are left uncovered with
paint.
Sagging
Thickness of painting should not be excessive. If too much thick
coat of paint is applied, the defect is known as sagging.
Wrinkling
This defect occurs in thickly painted surfaces.
Saponification
Defect of formation of soap patches on the painted surface is
known as saponification. This defect occurs due to chemical
action of the alkalies.
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Varnishes
Varnish - is a transparent or nearly
transparent solution of resinous material
and oil, alcohol or turpentine to form a
clear, tough, glossy film on woodwork.
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Components of
Varnish
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Functions of Varnish
Varnish performs the following functions :
It brings about brilliance to the painted
surface.
It protects the surface against adverse effects
of the atmosphere.
It increases the durability of the paint film.
It beautifies the surface without hiding the
beautiful grains of the wood.
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Properties of Good
Varnish
A good varnish should possess the following
properties :
It should not hide the natural grains of the
surface.
It should not shrink or show cracks after
drying.
It should make the surface glossy. (iv) It
should dry rapidly.
It should impart the finished surface
uniform colour and pleasing appearance.
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Process of Varnishing
Following operations are required to be carried out while
varnishing a wooden surface :
1. Preparation of Surface
The surface to be varnished should be thoroughly rubbed
smooth by means of sand paper and thoroughly cleaned from
dust and dirt.
2. Knotting
It is the process by which knots on the surface of wood work are
killed by applying certain substance over the knots. All the knots
should be covered with a hot preparation of red lead or glue size.
3. Stopping
After knotting, the surface of wood work is stopped by means of
hot weak glue size. This coat fills all the pores of the surface.
After stopping when surface becomes dry, it is rubbed again with
sand paper.
4. Applying Varnish Coats
After stopping process, varnish is applied on the surface in very
thin coats. Next coat is applied only when previously applied coat
has dried. For varnishing, fine brittle varnishing brush should be 31
used.
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