Paints and varnishes

This presentation attempts to enlighten the reader about various kinds of paints and varnishes, their ingredients, uses etc.

1. P a i n t s & Varnishes BY PRANJAL SINGH

2. Let us start with Paints. What are Paints? Paints are coatings of fluid materials which are applied over surfaces which may be : POP Plastered Putty finished Of cement concrete Of Timber Of Metals Following are the objects of painting a surface: It protects the surface from weathering effects of the atmosphere and actions by other liquids, fumes and gases. It prevents decay of wood and corrosion of metal. It is used to give good appearance to the surface. The decorative effects may be created by painting and the surface becomes clean , colourful and attractive. It proves a smooth surface for easy cleaning.

3. Characteristics of an ideal paint Following are the characteristics of an ideal paint: It should possess a good spreading power i.e., maximum area of the surface should be covered by minimum quantity of the paint. The paint should be fairly cheap and economical. The paint should be such that it can be easily and freely applied on the surface. The paint should be such that it dries in reasonable time and not too rapidly. The paint should be such that its colour is maintained for a long time. The paint should form a hard and durable surface. The paint should not affect health of workers during its application. The paint should not be affected by weathering actions of the atmosphere. The paint should possess attractive and pleasing appearance. The surface coated with paint should not show cracks when the paint dries . When applied on the surface, the paint should form a thin film of uniform nature. Spray painting metal^ Painting wood

4. Ingredients of Paint A paint can have some or all of the following ingredients: Paint

5. Ingredients of Paint Base : A base is a solid substance in a fine state of division and it forms the bulk of paint. It determines the character of paint and imparts durability to the surface which is painted. It reduces shrinkage cracks formed on drying and it also forms and opaque layer to obscure the surface of material to be painted. Examples- White lead, Red lead, zinc oxide etc. 2. Vehicles or Carriers: The vehicles are the liquid substances which hold the ingredients of a paint in liquid suspension. They are required for mainly two reasons: To make it possible to spread the paint evenly and uniformly on the surface in the form of a thin layer; and To provide a binder for the ingredients of a paint so that they may stick or adhere to the surface. Examples- Linseed oil, Tung oil, Poppy oil (prepared from poppy seeds), Nut oil etc. < Linseed oil. It is extracted from flax seeds.

6. Ingredients of Paint Solvents or Thinners: The function of solvent is to make the paint thin so that it can be easily applied on the surface. It basically increases the fluidity of the paint. Thinner helps to penetrate into the porous surfaces, thereby making the paint smooth and easy to work with. Examples- Turpentine, naphtha, petroleum spirits, water etc. Colouring pigments: When it is desired to have a different colour than the base of the paint, a colouring pigment is to be added. The pigments are available in the form of fine powders in various colours and qualities. Some of the colouring pigments used to create particular tints of paints are Graphite (for black) prussian blue (for blue), Burnt umber, raw umber (for brown), chrome green (for green), Red lead (for red), raw sienna (for yellow) etc. Naphtha Chrome green pigment Prussian blue pigment Raw Umber Raw sienna powder

7. Ingredients of Paint 5. Additive and/or Drier: Additives are usually added in small quantities in different types of paints. They affect the properties of paint. These are also added to improve the paint properties, such as colour opacity, pigment dispersion, and stability. Driers are substances that accelerate the process of drying of paint. The various patented driers are available in the market. The litharge, red lead and sulphate of manganese can be used as driers. The litharge is the most commonly used drier. 6. Filler: Fillers are used to impart various physical properties other than colour i.e. opacity or texture or simply to make handling of paint better. They not only make the paint more durable but also reduce the costly base in paint, thereby making the paint economical. Litharge

8. Types of Paint Whitewash or Limewash - Whitewash is a low-cost paint made by adding water to a mixture of slaked lime. Generally we use it for the whitening of walls and ceilings. Colourwashing - Colourwashing is an application of a coloured limewash . To paint the wall in a specific colour and impart stability in paint, a colouring pigment and vehicle or binder like fevicol are added in the required proportion.

9. Colourwash (Coloured lime wash paint)

10. Types of Paint Distemper: A distemper is composed of base, carrier, colouring pigments and size (a thinned version of the adhesive). For base, the whiting or chalk is used and for carrier, the water is used. Hence distemper may also be termed as water paint. Thus it is more or less a paint in which whiting or chalk is used as base instead of white lead and the water is used as carrier instead of linseed oil. The surface to receive distemper is thoroughly rubbed and cleaned. After that a priming coat is applied and it is allowed to become dry. For ready made distempers, the priming coat should be composed of materials as recommended by the makers of distempers. For local made distempers, milk is used for priming coat. After priming coat, the first coat of distemper is applied. The second coat of distemper is applied after the first coat has dried and become hard. ` Some commercially available water based distemper paints are shown below.

11. Distemper-painted Interiors examples

12. Types of Paint Cement Paint: This paint consists of white cement, pigment and additives. It is available in dry powder form. The cement paint is available in a variety of shades and exhibits excellent decorative appearance. It is water proof and durable. It proves to be useful for surfaces which are damp at the time of painting or are likely to become damp after painting. It is desirable to provide cement paint on rough surface rather than on smooth surface because its adhesion power is poor on smoothly finished surface. `

13. Types of Paint Oil paint: Oil paint consists of a base like zinc oxide, red lead, iron oxide etc., colouring pigment, binder like linseed oil, poppy oil etc., thinner, drier and filler. This paint is generally applied in three coats of varying composition. They are respectively termed as primes, undercoats and finishing coats. Oil paints are glossy, smooth, durable and stain-resistant . Oil paint should not be applied while there’s a presence of moisture on walls’ surface or during humid weather. It is advisable to redecorate the surfaces finished with oil paint with a coating of fresh oil paint only. The layer of old oil paint serves as a foundation for the fresh paint. Nowadays, due to the availability of advanced types of house paints in the market, oil paints are rarely used.

14. Types of Paint ^Metal furniture painted with oil paint. Wood furniture painted with oil paint >

15. Types of Paint Emulsion Paint: This paint contains binding materials such as polyvinyl acetate, synthetic resins, etc. This paint is easy to apply and dries quickly in about 1.5 to 2 hours. It can be used on both exterior and interior surfaces. The colour of this paint is retained for a long period and the surface of paint is tough and it can be cleaned by washing with water. Emulsions are defined as a mixture of two liquids that don’t blend well. Two non-blending liquids can form different types of emulsions. Usually, in emulsion paints, water is available at around 50-60% by volume, rest are the oily portions and the solids in the form of pigments. 

16. Types of Paint Enamel Paint: This paint contains white lead or zinc white, oil, petroleum spirit and resinous matter. It dries slowly and forms a hard and durable surface. It is usually used to coat metallic and wooden finishes/surfaces. It has a hard, glossy and opaque finish. It can be painted on walls to protect them from tough conditions. This paint is resistant to water, stain and heat. It can be used for both internal and external walls. In order to improve the appearance, it is desirable to apply a coat of titanium white in pale linseed oil before the coat of enamel paint.

17. Types of Paint Aluminium Paint: In this paint, the very finely ground aluminium is suspended in either quick-drying spirit varnish or slow-drying oil varnish as per requirement. The spirit or oil evaporates and a thin metallic film of aluminium is formed on the surface. Following are the advantages of this paint: Visible in darkness. Resists heat to a certain degree. The surfaces of iron and steel are better protected from corrosion by this paint than any other paint. It possesses a high covering capacity. A litre of paint can cover an area of about 200 m². It gives good appearance to the surface. It is impervious to the moisture. It possesses high electrical resistance. It is widely used for painting gas tanks, hot water pipes, marine piers, oil storage tanks, radiators, etc. Aluminium painted vintage gas tank (bike) ^ Aluminium painted machinery

18. Types of Paint 8. Anticorrosive paint: This paint essentially consists of oil and a strong drier. A pigment such as chromium oxide or red lead or zinc chrome is taken and after mixing it with some quantity of very fine sand, it is added to the paint. The advantages of an anticorrosive paint are as follows: It is cheap. It lasts for a long duration. The appearance of the paint is black. 9. Bituminous Paint: This paint is prepared by dissolving asphalt or mineral pitches or vegetable bitumen in any type of oil or petroleum. A variety of bituminous paints is available. The paint presents a black appearance and it is used for painting ironwork under water.

19. Types of Paint Luminous Paint: Luminous paint  or  luminescent paint  is paint that exhibits luminescence. In other words, it gives off visible light through fluorescence, phosphorescence, or radio luminescence. The surface on which luminous paint is applied shines like radium dials of watches after the source of light has been cut off. The paint should be applied on surfaces which are free from corrosion or any other lead paint. This paint is of three types: 1. Fluorescent Paint 2. Phosphorescent Paint 3. Radio luminescent Paint

20. Types of Paint Luminous Paint Phosphorescent (glow in the dark) paints

21. Failure of Paint The failure of paint job on wall or wooden members or structural steelwork is not uncommon. The paint job, though an easy job, has peculiarities of its own. At the same time, a failed paint job involves substantial expenditure by way of scraping the old paint, repairing the surface and cost of new paint. Following are the causes of failure of a paint job: Bad workmanship: The paint job demands a certain degree of skill. A careless painter may be in the habit of thinning paint too much so that he can save material and labour both. The layer of paint can even be absent for portions of surface which are difficult to reach. 2. Conditions for painting: The job of painting should be carried out under favourable conditions. It should be seen that dirt, dust and moisture do not get entrapped during the process of painting. Also, very high or low temperatures and humidity during the application of paint can also seriously affect the performance of most of the paints.

22. Failure of Paint 3. Moisture: The leakage through sanitary installations, floors, roofs, water pipes, etc., make the painted surface moist and in case of newly constructed building, the water used during construction activity may require time to evaporate. Whatever may be the reason, the presence of moisture accelerates the process of separating the paint layer from surface. Salts and alkalies : The movement of moisture can transport salts from either internal volume of masonry or new deposits. Such salts and alkalies saponify [ turn (fat or oil) into soap by reaction with an alkali] the oil paints. Unsuitable surfaces: If the surfaces are not properly prepared or treated to receive the paint, it may lead to the failure of paint job. 6. Wrong choice of paint: Depending upon the climatic conditions, nature of surface to be painted and various other factors affecting the performance of paint, the choice of paint should be made. It is found that low quality paints are cheap in initial cost. But the durability of such painted surfaces is very poor.

23. Defects in Painting Following are the usual defects which are found in the painting work: Blistering: This defect is caused by water vapour which is trapped behind the painted surface. The formations of bubbles under the film of paint causes this defect. Blistering Blistering 2. Bloom: In this defect, the formation of dull patches occurs on the finished surface . It is due to the defect in paint or bad ventilation. Bloom Bloom

24. Defects in Painting Fading: The gradual loss of colour is known as the fading and it is mainly due to the effect of sunlight on pigments of paint. Flaking: A portion of the painted surface is sometimes seen loose. It is known as flaking and is due to poor adhesion. Fading Flaking of paint

25. Defects in Painting Flashing: Sometimes the glossy patches are seen on the painted surface. This is known as the flashing and it is mainly due to poor workmanship, cheap paint or weather actions. Grinning: When the final coat of paint has not sufficient opacity, the background is clearly visible. This is known as grinning . Sagging: When a vertical or inclined surface is too thickly painted, the defect of sagging occurs. Grinning Sagging Flashing

26. Defects in Painting Saponification: The formation of soap patches on the painted surface is termed as the saponification and it is due to chemical action of alkalies . Wrinkling: The surface of the paint which wrinkles and gathers together is called wrinkling paint.  It forms a layer like undulating waves on the painted surface. The main reason behind an appearance of waves can be application of too much paint or the oil in the paint is more than required. Wrinkling paint is more noticeable with enamels and varnishes. Saponification Wrinkling Wrinkling

27. Storage of paints Paint can be kept fresher for longer by following the points mentioned below: Paint should always be kept in securely closed containers where the air can’t spoil it. If one is halfway through painting and needs to store tins that are half full or more, lid should be removed and top covered with cling wrap. After that lid should be replaced and the paint product should be labelled with name and manufacturer, colour name or code, and date last used. In case of leftover paint, tins less than half full can be decanted into smaller containers with tight lids. Again, care should be taken to label the lid with the details as above. Paint is best stored at a constant temperature, away from direct sunlight and in a frost-free environment.

28. Now let us learn about Varnishing The term varnish is used to indicate the solution of resins or resinous substances prepared either in alcohol , oil or turpentine. Following are the main objects of applying varnish on a wooden surface: It brightens the appearance of the grain in wood. It renders brilliancy to the painted surface. It protects the painted surface from atmospheric actions. It protects the unpainted wooden surfaces of doors, windows, roof trusses, floors, etc., from the actions of atmospheric agencies.

29. Characteristics of an ideal varnish Following are the characteristics of an ideal varnish: It should render the surface glossy. It should dry rapidly and present a finished surface which is uniform in nature and pleasing in appearance. The colour of varnish should not fade away when the surface is exposed to atmospheric actions. The protecting film developed by varnish should be tough, hard and durable. It should not shrink or show cracks after drying.

30. Ingredients of a varnish Following are the ingredients of a varnish: Resins or resinous substances: The commonly used resins are copal, lac or shellac and rosin. The copal is a hard substance and is available from the earth at places where pine trees existed in past. It is available in variety of forms. The lac or shellac is obtained by exudation of some types of insects in India. The rosin is obtained from pine trees. Other resins are amber, mastic, gum dammar, etc. Driers: The function of a drier in varnish is to accelerate the process of drying. The common driers used in varnishes are litharge, lead acetate etc. v Copal resin Shellac Rosin v Lead acetate

31. Ingredients of a varnish Solvents: Depending upon the nature of resin, the type of solvent is decided. Following table shows the solvent for different resins. No. Solvent Resins 1. Boiled linseed oil Amber, Copal 2. Methylated spirits of wine Lac or shellac 3. Turpentine Mastic, Gum dammar, Rosin 4. Wood naphtha (Methanol) Cheap varieties of resins

32. Types of varnishes Depending upon the solvent, the varnishes are classified into the following four categories: Oil varnishes: In this type of varnish, the hard resins such as amber and copal are dissolved in linseed oil and if the varnish is not workable, a small quantity of turpentine is added. The oil varnishes dry slowly but they form hard and durable surface. In fact these are the hardest and most suitable varnishes. They are specially adopted for exposed works which required frequent cleaning. They are used on coaches and fittings in houses. Spirit varnishes: Resins of soft variety such as lac or shellac are used with methylated spirit of wine as solvent in this type of varnish. These varnish dry quickly but are not durable and are easily affected by weathering actions. These are greatly used for furniture. The French polish is a variety of this class of varnish and the desired colouring tinge can be obtained by addition of suitable colouring pigment. < A commercially available variety of French polish.

33. Types of varnishes  French polishing is a method of applying shellac based spirit varnish to wood furniture, musical instruments, or decorative accents in many thin layers—typically well over 100—that results in a highly glossy, glass-smooth surface with a rich depth that beautifully highlights the grain of the wood. The French polish is one of the finest finish for ornamental furniture prepared from superior quality of wood. ^ Furniture before and after using French polish

34. Types of varnishes Turpentine varnishes: The turpentine is used as solvent in this type of varnish. The resins adopted are of soft variety such as gum dammar, mastic and rosin. These varnishes dry quickly and possess light colours. They are not durable and tough as oil varnishes. Water varnishes: The shellac is dissolved in hot water and enough quantity of either ammonia or borax or potash or soda is added such that shellac is dissolved. These varnishes are used for varnishing maps, pictures, etc. They are also used for delicate internal work and as a covering for wall paper.

35. Process of varnishing Preparation of surface: The woodwork is thoroughly rubbed down by means of sand paper or pumice stone. The surface is then made smooth and clean. Knotting: The process of knotting is then carried out. [The term knotting is used to indicate the covering or killing of all knots in woodwork with a substance through which the resin cannot exude or come out.] Stopping: The surface of woodwork is then stopped. This is done by means of hot weak glue size. It will fill up the pores on the surface. Alternatively, the boiled linseed oil can be applied in two coats. When the surface becomes dry it should once again be dubbed down with sandpaper. Coats of varnish: The varnish is then applied on the surface in thin coats. The next coat is applied after the previous one has thoroughly dried up. The varnishing should not be done with ordinary paint brushes. But fine haired varnishing brushes should be used. The application of varnish on the woodwork is carried out in the following way:

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