1. Building Materials Building stones Bricks and clay products
Timber and wood products
Paints, varnishes
Metals and alloys
Plastics and fibers
Glass
Asphalt, bitumen and tar
Cement concrete
Insulating Materials
Miscellaneous Materials

2. Paints and Varnishes

3. Learning Objectives Definition Functions of paints.
Composition of oil paints.
Preparation of oil paints.
Characteristics of good paints.
Types of paints, and properties of paints
Defects in painting.

4. Definitions
Paint is a coating of fluid material applied over timber and metal surface as protective coating which on drying forms a thin film on surface
Paint is a mixture of liquid or medium and a coloring or pigment to impart color and provide protective coating to the surface
Oil based paints are polymers or pre-polymer solutions which form a film upon evaporation of the solvent
Paint is a dispersion of pigments in a drying oil, with addition of driers and thinners

5. Definitions
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
Enamel. Bases like zinc oxide ground in varnish. Dry quickly to furnish hard glossy finish.

6. Definitions
Distemper is a comparatively cheap decorative paint for walls and ceilings applied on brickwork, or plastered surfaces
Water Wash and Color Wash. Fresh lime slacked with water, mixed thoroughly, screened and added with glue and may be a pigment

7. Definitions
French Polish. Type of spirit varnish prepared by dissolving resin in methylated spirit at room temperature for use on hardwood substances to hide grain defects.
Wax Polish. Bees wax dissolved in turpentine used for highlighting the grain over wooden surfaces.

8. Functions of Paints
To protect the surface from weathering effects of the atmosphere and actions by other liquids, fumes and gases
To provide pleasing, colorful and decorative appearance to the surfaces
To prevent decay of wooden members
To prevent corrosion of metallic surfaces
To provide a smooth surface for easy cleaning

9. Classification of Paints

10. Classification of Paints

11. Types of Paints Oil Paint: ordinary paint
Bituminous paint: prepared by dissolving asphalt or bitumen in oil or petroleum
Cement paint: It consists of cement and hydrated lime mixed along with a coloring pigment
Colloidal paint: a paint with no inert material
Aluminum paint: aluminum powder suspended in spirit varnish or oil varnish
Asbestos paint: peculiar type, applied to places exposed acidic gases and steam.
Cellulose paint: prepared from nitro cotton celluloid sheets

12. Types of Paints
Emulsion paint: It consists of polyvinyl acetate and synthetic resin as binding material
Enamel paint: It consists of white lead ground in small quantity of oil and mixed with petroleum spirit and resinous matter
Graphite paint: black in color, applied on iron surfaces
Luminous paint: contains calcium sulphide with varnish
Silicate paint: prepared by mixing calcined ground silica with resinous substances
Anti-corrosive paint: consists of oil and strong drier
Plastic paint: variety of plastic present, applied using brush or spray painting.
Synthetic rubber paint: prepared from resin

13. Composition of Oil Paints
Constituents of oil paints
Base
Vehicle – an oil, generally linseed oil
Coloring pigment (s)
Solvent or thinner
Drier
Inert filler
By suitable variation of the type and proportion of various constituents the paints are made as
Dry
Glossy
flat

14. Composition of Oil Paints - Base
Base : principal constituent, a solid matter forming the main body of paint and possessing binding properties.
White lead, red lead, zinc oxide, iron oxide, metallic powders of aluminum, copper and bronze, etc
Makes the paint film harder and more resistant to abrasion
Forms an layer to obscure the surface
Reduces shrinkage cracks on drying

15. Composition of Oil Paints - Base
White lead
Cheapest and most commonly used base
Greater covering power than all others
Dense so good to obscure surfaces
Weathers well
Not suitable for delicate works as gets discolored
Not suitable for painting of iron work due to rusting

16. Composition of Oil Paints - Base
Red lead
Sticks well and protects against rusting. With oil considered best for first coat or prime coat
Good drier for linseed oil
Lead paints are poisonous. Precautions needed while spraying or scrapping paint

17. Composition of Oil Paints - Base
Zinc oxide or Zinc white
Not affected by weather
Takes a fine polish hence good for decoration works
Not poisonous
Less durable and more costly than lead based
Iron oxide
Used basically in finishing coat for iron work
Prevents rust formation
Comparatively cheaper
Tints vary from yellowish brown to black

18. Composition of Oil Paints - Vehicle
Vehicle: Carrier liquid which carries solid materials of base and helps them to spread evenly on the surface to be painted. Linseed oil, poppy oil, nut oil, soyabean oil, fish oil, latex emulsions
Oily liquid in which base and pigment are soluble
Facilitates the paint to be conveniently spread evenly over the surface
Acts as a binder for the base and causes it to stick to the surface
On drying forms a tough and elastic film

19. Composition of Oil Paints - Vehicle
Raw linseed oil
Thin, pale and transparent oil
Sweet taste, no smell
Becomes hard and stiff on exposure to air
When spread in thin film, looks like varnish
Dries very slowly
Used for painting delicate interior work and wood work

20. Composition of Oil Paints - Vehicle
Boiled linseed oil
Thicker and darker in color (deep amber to rich brown)
Dries quickly. On drying leaves a hard, glossy and durable surface
Has more area coverage capacity
Used for exterior work
Double boiled linseed oil
Light in color as raw linseed oil but with different smell
Dries quicker and gives better results
Requires and thinning agent like turpentine oil

21. Composition of Oil Paints - Pigment
Coloring pigments: finely divided solid coloring matter to provide shade, color to paint
Blacks: lamp black, vegetable black, ivory black
Blues: indigo, Prussian blue
Yellows: chrome yellow, raw Siena, yellow ochre
Greens: copper sulphate
Browns: raw umber, burnt umber
Red: red lead, vermillion, carmine

22. Composition of Oil Paints - Thinner
Solvent or thinner: A volatile liquid added to prepare paint to increase fluidity thus workability and ease of application
Thinner helps penetration of paint in porous surfaces
Turpentine oil is most common thinner
Excessive thinner dulls the colors and gloss
Excessive thinner reduces protective value of paint

23. Composition of Oil Paints - Drier
Drier: added to paint to quicken the drying of vehicle
Linseed oil dries by absorbing oxygen
Drying process expedited by adding oxygen rich substances
Common driers are: Litharge, Red lead, Lead acetate, Manganese dioxide, Zinc sulphate
Excessive drier destroys the elasticity of paint and causes flaking
Drier is added to the paint just before use

24. Composition of Oil Paints - Filler
Inert filler
An adulterant mixed to replace the base in part thus reducing the cost of paint
Commonly used fillers are silica, charcoal, powdered chalk, aluminum silicate, barium sulphate, etc

25. Characteristics of Good Paints
Should have a good body or spreading power
Should work smoothly and freely to be laid in thin coat
Should form durable, tough and wear resistant film upon drying
Color should not fade or change
Painted surface should dry in about 9 hours
Should become hard enough in 24 hours to take up another coat
Should not crack upon drying
Should give a smooth and pleasing finish
Should dry quickly
Should not damage the painted surface

26. 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 seive

27. Defects in Painting
Cracking: cracks extending throughout the entire thickness of paint, due to
Improper seasoning of wood
Excessive use of drier
Application of too many coats
Crazing and crocodiling: Hairline cracks in top coat, due to
Use of excessive oil
Use of impure oil
Insufficient drying of under coat

28. Defects in Painting Blistering and peeling: Runs and sage:
Exposure of paint to strong sunshine
Leaving oil or grease on the surface to be painted
Painting a surface with moisture on surface or in pores of wood
Runs and sage:
Application of too thick or slow drying paint
Painting over a glossy surface
Use of excessive drier
Excessive humidity or rapid thermal changes during drying period

29. Defects in Painting Chalking: rub off with hands or clothes
Use of insufficient oil in priming coat
Washing off: deposition of water soluble dissolved matter at lower edges forming streaks
Dull appearance: caused by use of excessive drier or on aging

30. Defects in Painting Slow drying: Yellowing of white paint:
use of inferior or old oils
Painting over damp surfaces
Painting during unfavorable weather
Yellowing of white paint:
Use white enamel where glossy finish is desired
For indoors use linseed oil with yellow tint that does not bleach unless exposed to sunshine

31. Questions ???