2. Paints:Paints are used to protect metals, timberor plastered surfaces, brick work andconcrete work from the corrosive effectsof weather, heat, moisture or gases etcand to improve their appearance.Composition of the paints can be easilyadjusted in the process of theirmanufacture, depending upon thepurpose for which they are required andquality of the work required.
3. • CONSTITUENTS/ COMPOSITION OFPAINTS:Paints essentially contain a base whichprovides body, there is a carrier, also known asvehicle in which the base is dissolved, and it isthe carrier which helps the base to spread allover when applied. The pigments are alsoadded to give the desired colours. Somecommon examples of substances used as basein paint are zinc white, white lead, red lead.Common substances used as carrier in thepaints is such as, water (in water paints),linseed oil and poppy oil etc.Continued -------
4. Besides these essential ingredients, severalother substances are added, such as fillers togive bulk to the paint without affecting itsproperties and to make it economical, solventsor thinners which dissolve other constituentsand make the paint thin and driers which helpin rapid drying, setting and hardening of thepainted surface. Some commonly used fillersfor paints are chalk, silica and charcoal,commonly used solvents are turpentine oils,petroleum sprit, commonly used driers are redlead, litharge and manganese sulphates etc.
5. USES OF PAINTS:The main functions performed by paints are:• It is used to give a high-class finish,• It is used to give attractive colours,• It is used to give pleasing surfaces design andappearance,• It is also used to protect the material fromatmospheric effects,• To protect various substances from corrosion,• To protect wooden articles from wet-rot and manyother types of defects,• To make the materials long lasting.
6. PROPERTIES OF GOOD PAINTS :The main properties of a good paint are as follows:• It should give a thin and uniform coating.• It should be hard and durable on drying.• The painted surface should not crack on drying.• It should be resistant to weathering and corrosiveaction.• It should be water-repellent (except water paints).• It should have good spread.• It should have good adhesive power. It should give agood finish with attractive colour, design andappearance.• The colours should be fast and permanent.• It should be cheap and economical.
7. CLASSIFICATION OFPAINTS:Paints in common use areclassified as:
8. (1) Oil Paints:The oil paints are very widely and commonlyused for painting wooden and metallicsurfaces in all kinds of engineering, industrialand other decorative works. In these paintsvarious oils like linseed oil, poppy oil andcastor oil etc are used as carrier. These paintsare available in different colours and underdifferent trade names. While using thesepaints it is proper to give two to three coatingsso as to obtain good results.
9. (2) Plastic Paints:• In addition to other ingredients this paintcontains the requisite amount of plastic.That is why; all such paints are known asplastic paints.• Plastic paints are used wherever highclass work is required, such assophisticated buildings, show-rooms,theatres and auditoriums. They can beeasily applied on the plastered walls.
10. (3)Cement Paints:• The cement paint essentially consists of WhiteCement (about 70%), Hydrated Lime (about 15%),Pigments (about 5 to 8%), Sodium or Calciumchloride as the hygroscopic salts (about 5%) andsmall amount of about 1% aluminium. These paintsare made available in powder form. Water is addedto the paint just before use. It is necessary to mixthe paint from time to time while using it. Theplastered surface to be painted, like walls etc arefirst made wet. As the painted surface dries, wateris again sprinkled over it for proper setting of thepaint.• Cement paints mainly used over the plasteredsurfaces.
11. (4) Bituminous Paints:Bituminous paints are prepared bydissolving bitumen in petroleum orother solvent oil. These blackcoloured paints leave hard, toughand elastic surfaces. These arehighly resistant to water and arespecially used for submerged ironand steel structures.
12. (5) Water Paints:A water paint is the mixture of pigment,binder, drier and water (the carrier).Casein is the most common binder usedin these paints. A variety of pigments areused to obtain different colours. Thesepaints are cheap, easily workable andalso washable when properly set. Theyalso give a good finish and are suitablefor the inside walls.
13. (6) Distemper Paints:Distemper consists of chalk (finely powdered),pigment and glue (animal glue). These are inpowder form and available in a large variety ofattractive shades. Sometimes these are available inthe form of paste also (with the addition of linseedoil). These are mixed with water at the time of useand applied on the plastered surfaces (like walls,ceilings etc) with brushes. These may beconsidered as superior quality water paints.However they give a better finish and are longlasting. They are suitable for high-class interiordecorative finishing work on the walls and ceilingsof all kinds of buildings.