A coloured substance which is spread over a surface and dries to leave a thin decorative or protective coating

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PAINTS
Definition:-
Paint is a substance composed of solid coloring matter suspended in a liquid
medium and applied as a protective or decorative coating to various surfaces, or to canvas or
other materials in producing a work of art.
History:-
Humans have felt the need to leave their mark on the world in the form of painted
images since prehistory. If we look at how art evolved over the years we can know a number of
things about the people that created them and the societies they lived in. At some point early
man figured out that by mixing colour giving particles known as pigments into a medium like
water or saliva- paint was invented. Cave dwellersusedcrude paintstoleave behindthe graphic
representationsof theirlivesthateventodaydecorate the wallsof theirancientrockdwellings.

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5000 years ago Blue Frit was the first synthetic pigment being produced by the Egyptians. The
paint and coatings industry, however, had to wait for the Industrial Revolution before it became
a recognized element of the American national economy. The first recorded paint mill in
America was reportedly established in Boston in 1700 by Thomas Child. A century and a half
later, in 1867, D.R. Averill of Ohio patented the first prepared or “ready mixed” paints in the
United States. In the mid-1880s, paint factories began springing up in population and industrial
centers across the nation. Mechanization was making the manufacturing process accessible to a
larger and less specialized group of entrepreneurs. The weight of prepared paint makes it
expensive to transport, so a decentralized structure of small manufacturers in discrete markets
dominated the industry until the mid-1900s.
Ingredients Of Paint:-
1. Base:-
Base is a solid substance that forms the body of the paint and usually consists of finely
divided suitable material. It determines the character of the paint and imparts durability to
the surface. The function of the base material is to make the ultimate filmharder and elastic,
prevent formation of shrinkage cracks and protect the surface from moisture as well as ultra
violet rays.
Example: Red lead, Zinc white, White lead, Oxide of iron, Titanium white or Titanium
dioxide, Antimony white, Aluminum powder, Lithopone, etc.
2. Vehicles:-
Vehicles are the liquid substances which hold the ingredients of paint in liquid suspension.
They serve mainly two purposes:
 To make it possible to spread the paint evenly and uniformly on the surface in the form
of a thin layer.
 To provide a binder for the ingredients of a paint so that they may stick or adhere to the
surface.
Example: Poppy oil, Nut oil, Linseed oil, Stand oil, Tung oil, etc.
3. Driers:-
These act as catalysts. These are substances that are used with a view of accelerating
the rate of drying of the paint film. A drier absorbs oxygen from the air and transfers it to the

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vehicle, which in turn gets hardened. Driers may be either in the form of soluble driers or
paste driers. Soluble driers are compounds of cobalt, lead, manganese, etc. dissolved in
linseed oil or some other volatile liquid. Paste driers are compounds of the same metal.
Example: Litharge, red lead and sulphate of manganese, etc
4. Solvents:-
They are volatile substances that are added to the paint in order to make their
application easy and smooth. Solvents help the paint in penetrating through the porous
surface. The most commonly used solvents are spirit and turpentine. Solvents are also
known as thinners from their function of thinning the original paint which is highly viscous.
They are added to reduce the property of paint blistering. They also help the paint to
penetrate through the porous surface and they increase the spreading power of the paint.
After application, the solvent evaporates and the resulting surface is more even and smooth.
5. Colouring Pigments:-
Colouring pigments These are the colouring materials added to the paints in order to
impart a desired shade and colour. They are added in the finely powdered state.
Manufacturing:-
 Making the paste:-
Pigment manufacturers send bags of fine
grain pigments to paint plants. There, the pigment is premixed
with resin (a wetting agent that assists in moistening the pigment),
one or more solvents, and additives to form a paste.
 Dispersing the pigment:-
The paste mixture for most industrial and
some consumer paints is now routed into a sand mill, a large
cylinder that agitates tiny particles of sand or silica to grind the
pigment particles, making them smaller and dispersing them
throughout the mixture. The mixture is then filtered to remove the
sand particles. Instead of being processed in sand mills, up to 90
percent of the water-based latex paints designed for use by
individual homeowners are instead processed in a high-speed dispersion tank. There, the

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premixed paste is subjected to high-speed agitation by a circular, toothed blade attached to
a rotating shaft. This process blends the pigment into the solvent.
 Thinning the paste:-
Whether created by a sand mill or a dispersion tank, the paste must
now be thinned to produce the final product. Transferred to large kettles, it is agitated with
the proper amount of solvent for the type of paint desired.
 Canning the paint:-
The finished paint product is then pumped into
the canning room. For the standard 8 pint (3.78 liter) paint can
available to consumers, empty cans are first rolled horizontally onto
labels, then set upright so that the paint can be pumped into them. A
machine places lids onto the filled cans, and a second machine
presses on the lids to seal them. From wire that is fed into it from
coils, a bailometer cuts and shapes the handles before hooking them
into holes precut in the cans. A certain number of cans (usually four)
are then boxed and stacked before being sent to the warehouse.
Types of paints:-
Paints in common use are classified as oil paints, water paints, cement paints and
bituminous paints. There are some “special paints” used for special purposes e.g. heat resisting
or fireproof paints, chlorinated rubber paints (for protection against acid fumes etc.), luminous
paints (for visibility of painted surfaces in the dark) etc
 Enamel paints:-
These paints are available in numerous
shades. They mainly consist of white lead or zinc white,
resinous matter and petroleum spirit. Their formation
into hard, impervious, decay-resistant enamel-like
surface soon after application protects it from being
affected by acids, alkalies, fumes and gas, hot and cold
water, etc. They can be used for internal as well as
external purposes.

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 Cement paints:-
These include a variety of paints in
which cement is the main constituent responsible for
the hardness and durability of the painted surface.
They are available in dry, powder form. They are
waterproof. It is desirable to provide cement paint on
a rough surface rather than a smooth surface because
its adhesion power is more on rough surface than on
smooth surface. They prove to be economical as compared to oil paints. They are suitable for
painting fresh plasters having high alkalinity because cement paints are not likely to be
attacked by the alkalinity of the masonry surface. It is not necessary to remove the existing
paint for the application of new paint
 Oil paints:-
They are generally applied in three different
layers with varying composition. These are termed as
primes, undercoats and finishing coats. The dampness of
the wall affects the life of the oil paint, hence it must not
be applied during damp weather.
 Cellulose paints:-
They are prepared from nitro cotton,
celluloid sheets, photographic films, etc. The cellulose
paints harden by evaporation of thinning agents. The
surface painted with cellulose can be washed and cleaned
easily. They are little costlier than other paints.
 Aluminum paints:-
Finely ground aluminum is suspended in
either quick-drying spirit varnish or slow-drying oil varnish
as per requirement. As the spirit or oil evaporates, a thin
film of aluminum is formed on the surface. This paint forms
a better protective surface over steel and iron. They are
impervious to moisture and possess high electrical
resistance. They have a good appearance and are visible in darkness.

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 Emulsion paints:-
These paints contain polyvinyl acetate,
synthetic resins, etc. They are easy to apply and are
retained for a long period and can be cleaned easily with
water. For a rough plastered surface, a thin coat of cement
paint may be first applied to smoothen the surface. It is
necessary to have a sound surface to receive the paint.
 Anticorrosive paints:-
These consist of oil and a strong drier.
The pigments such as chromium oxide, lead or zinc
chrome is taken and after mixing it with a small quantity
of very fine sand it is added to the paint. These are cheap
and last for a long duration. They are black in colour.
 Synthetic rubber paints:-
These paints are prepared from
resins. They have an excellent chemical resistant
property. They can be applied to surfaces that may not
be completely dry. They offer good resistance to water
and are not affected by heavy rains. They dry very
quickly. They are not affected by weather and sunlight
and are quite easy to apply.
Properties of good paint:-
i. It should have a body or spreading power.
ii. It should work smoothly and freely and be capable of being laid in a thin coat with the
brush.
iii. It should form durable, tough and resistant to wear film on drying.
iv. Colour of paint should not fade or change.
v. It should become surface dry in about 9 hours and hard enough to take up another coat
in 24 hours.
vi. It should not crack on drying.
vii. It should give a smooth and pleasing appearance showing no brush marks on drying.
viii. It should dry quickly.
ix. It should not damage the painted surface.

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Method of Application:-
The method of application is largely dependent on the type of coating
selected. The most widely used methods of applying protective coatings are brush, roller,
conventional (air) spray, conventional (pressure-pot) spray and airless spray. The advantages
and disadvantages of these methods are briefly discussed below. Other, less widely used
methods include trowel, putty knife.
 Brush Application:-
Brush application should always be
undertaken using an appropriately sized,
good quality synthetic or natural fiber brush
compatible with the product being applied.
This application technique is relatively slow
and is generally used for coating small areas
with decorative paints and for surface
tolerant primers, where good penetration of
rusty steel substrates is required. It is
particularly suitable for the application of stripe coats and for coating complex areas where
the use of spray methods would lead to considerable losses due to overspray and associated
dry spray problems. Note that most high build coatings are designed for application by airless
spray; high filmbuild will generally not be achieved by brush application. In general, twice as
many coats will have to be applied by brush to achieve a similar build when compared to
airless spray. Brush application requires considerable care when applying non-convertible
coatings over one another, e.g. chlorinated rubber over chlorinated rubber, or vinyl on top of
vinyl. In these cases, the solvents in the wet coat readily redissolve the previously dry bottom
coat. Even a mild degree of the brushing out normally given to topcoats will cause pick-up of
the previous coat and result in a very poor finish. Even, light strokes should be used in these
circumstances, covering a particular area with one or two brush strokes, and on no account
working the bristles into the previous coat.
 Roller Application:-
Roller application is faster than brush on large, even surfaces and can be used for
the application of most decorative paints. However, control of film thickness is not easily
achieved. As with brush, high filmbuild will generally not be attained. Care must be taken to
choose the correct roller pile length, depending on the type of paint and degree of roughness of

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the surface. Typically, phenolic core rollers
should be used, fitted with a smooth to
medium pile roller cover and the roller cover
should be pre-washed to remove any loose
fibres prior to use.
 Air Spray (Conventional):-
This is a widely accepted, rapid method of coating application in which
paint is atomized by a low pressure air stream. Conventional air spray equipment is relatively
simple and inexpensive, but it is essential to use the correct combination of air volume, air
pressure and fluid flow to give good
atomization and a paint film free from
defects. If conventional spray application is
not controlled correctly, large losses of paint
can result from overspray and rebound from
the surface, in addition to problems such as
poor flow, sagging and pin holing. The major
disadvantage of conventional air spray is that
high build coatings can generally not be
applied by this method, as most paints have to be thinned to a suitable viscosity for
satisfactory atomization, and so lose their high build properties.
Uses:-
 It protects wood from decaying.
 It renders surface hygienically safe and clean.
 It gives decorative and attractive appearance to the surface.
 It protects the surface from weathering effects of the atmosphere and the actions by
other liquids, fumes and gases.
 It prevents decay and corrosion in metal.
 It provides a smooth surface.

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References:-
 Engineering Material by Surendra Singh
 Basic Civil Engineering by Satheesh Gopi
 Paints and protective coatings (by Dept. Of Defense, USA)
 http://mocomi.com/history-of-paint/
 http://www.paint.org/about-our-industry/history-of-paint/
 http://www.madehow.com/Volume-1/Paint.html
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