2. What is paint?
• Coatings of fluid materials
• Applied over surfaces of timber and metals
3. Constituents of Paint
• Base- solid substance in fine powdered form
- forms bulk of paint
- generally metallic oxides
- provides opaque coating
• Vehicle/carrier- liquid substances
- hold ingredients of paint in liquid suspension
- it makes possible to spread paint evenly on surface
- eg- linseed oil, poppy oil, tug oil, etc.
4. • Drier- accelerate process of drying and hardening; extracts oxygen
from atmosphere and transfer to vehicle
- reduces elasticity of paint; should not be used in final coat
- eg cobalt, lead, manganese dissolved in volatile liquid
litharge(PbO), sulphates of zinc and manganese
• Coloring pigment- added to base to have desired colors
• Solvents/ thinners- added to make paint thin so that it can be applied
on surfaces
- commonly used is spirit of terpentine
5. Characteristics of an ideal paint
• Should possess good spreading power i.e. maximum area of the
surface should be covered by minimum quantity of paint
• Should be fairly cheap and economic
• Should be such that it dries in reasonable time
• Should be such that its color is maintained for a long time
• Should form hard and durable surface
• Should not affect health of workers during its application
• Should not show cracks when it dries
• Should not be affected by weathering actions of atmosphere
6. Types of paint
• ALUMINIUM PAINT
• Finely ground aluminium is suspended in spirit varnish; the spirit evaporates
and a thin metallic film of aluminium is formed on surface
• Advantages:
• Visible in darkness
• Resist heat to a certain degree
• Possesses high covering capacity
• Gives good appearance to the surface
• Impervious to moisture
• Possesses high electrical resistance
• Used for painting gas tanks, hot water pipes, marine piers, oil storage tanks
7. • ANTICORROSIVE PAINT
• Consists of oil and strong drier
• Advantages:
• Cheap
• Lasts for long durations
• Appearance of paint is black
• ASBESTOS PAINT
• Peculiar type of paint
• Applied on surfaces exposed to acidic gases and steam
• BITUMINOUS PAINT
• Prepared by dissolving asphalt in any type of oil or petroleum
• Presents black appearance
• Used for painting ironwork under water
8. • CELLULOSE PAINT
• Prepared from nitro-cotton, celluloid sheets, photographic films, etc.
• Hardens quickly by evaporation of thinning agents
• Costlier than ordinary paint
• Presents flexible, hard and smooth surface
• Surface painted with this paint can be washed and easily cleaned
• COLLOIDAL PAINT
• Requires more time to settle
• During settlement, it penetrates through surface
• Used for interior and exterior walls
• EMULSION PAINT
• Easy to apply
• Dries quickly in about 1 ½ to 2 hrs
• Color is retained for long period
• Possesses excellent alkali resistance
9. • ENAMEL PAINT
• Dries slowly
• Forms hard and durable surface
• Surface with this paint is not affected by acids, alkalies, steam, hot or cold
water, etc
• Used for external and internal walls
• To improve appearance, apply a coat of titanium white in pale linseed oil
before applying enamel paint
• GRAPHITE PAINT
• Presents a black color
• Applied on iron surface which come in contact with ammonia, chlorine,
sulphur gases, etc.
• Used in mines and underground railways
10. • OIL PAINT
• Ordinary paint
• Generally applied in three coats (primes, undercoats, finishing coats)
• Cheap and easy to apply
• Possesses good opacity and low gloss
• Should not be applied during humid and damp weather
• PLASTIC PAINTS
• Contain necessary variety of plastic
• Possesses pleasing appearance and it is attractive in color
• Used for show rooms, auditoriums, etc.
• Water evaporates and a film of binders, pigments and other solids is left
behind
11. • CEMENT PAINT
• Consists of white cement, pigment, accelerator and other additives
• Available in dry powder form in variety of shades
• Exhibits excellent decorative appearance
• Water-proof and durable
• Desirable to provide cement paint on rough surface rather than on smooth
surface because its adhesion power is poor on smoothly finished surface.
• Advantages:
• Requires less skill and time for its application
• Preparation of surface is easy
• Can be applied over new and damp walls
• Economical than oil paints
• Dry rapidly than oil paints
12. • SYNTHETIC RUBBER PAINT
• Prepared from resins
• Offers great resistance to water; not affected by heavy rains
• Dries quickly
• Little affected by weather and sunlight
• Uniform color is maintained
• Moderate in cost
• Possesses chemical resisting property
13. Defects in painting
• Blistering
• formation of bubbles under the film of paint
• caused by water vapour trapped behind painted surface
• Bloom
• Formation of dull patches on finished polished surface
• Caused due to defect in paint or bad ventilation
• Fading
• Gradual loss of color
• Caused due to effect of sunlight on pigments of paint
• Flaking
• Portion of painted surface getting loosen
• Caused due to poor adhesion
• Wrinkling
• When horizontal surface is too thickly painted
14. • Sagging
• When vertical or inclined surface is too thickly painted
• Flashing
• Glossy patches on painted surface
• Caused due to poor workmanship, cheap paint or weather actions
• Grinning
• Background can be clearly seen
• Caused due to insufficient opacity of final coat of paint
• Running
• Paint runs back and leaves small areas of surface uncovered
• Occurs when surface to be painted is too smooth
• Saponification
• Formation of soap patches on painted surface
• Caused due to chemical action of alkalies
