Paints and Varnishes MCQ Quiz - Objective Question with Answer for Paints and Varnishes - Download Free PDF

Concept-

The usual defects which are found in the painting work are-

Blistering:

• This defect is caused by the water vapour which is trapped behind the painted surface. The formation of bubbles under the film of paint occurs in this defect. It may occur from various causes such as imperfect seasoning of timber, excess oil used in final coat etc.

Bloom:

• In this defect, the formation of dull patches occurs on the finished polished surface. It is due to the defect in paint or bad ventilation.

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 small portion of the painted surface is sometimes seen loose. It is known as the flaking and is due to poor adhesion.

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 seen. This is known as the grinning.

Running:

• The paint runs back and leaves small areas of surface uncovered. This defect occurs when the surface to be painted is too smooth.

Sagging:

• When a vertical or inclined surface is too thickly painted, the defect of sagging occurs.

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:

• When a horizontal surface is too thickly painted, the defect of wrinkling becomes prominent.

Explanation:

The Metallic Oxide Used in the Form of Powder in Paints (Base)

Definition: The metallic oxide used in the form of powder in paint is called the Base. In the context of paint formulation, the base is one of the essential components that provide the paint with its desired properties. It is generally a metallic oxide or compound that serves as the main pigment and provides opacity, durability, and protection to the surface being painted.

Role of the Base in Paint:

• Opacity and Hiding Power: The base is responsible for the paint’s ability to hide the surface underneath. It scatters light and provides a uniform appearance to the painted surface.
• Durability: The base imparts durability to the paint, making it resistant to environmental factors such as moisture, sunlight, and corrosion.
• Protection: The base helps protect the underlying surface from damage caused by environmental exposure, including oxidation, rust, and wear.
• Adhesion: It improves the adhesion of the paint to the surface, ensuring that the paint stays on the substrate for a longer period.
• Color and Aesthetic Appeal: While the primary role of the base is not to provide color, metallic oxides like titanium dioxide, zinc oxide, or iron oxide are often used as bases because of their ability to enhance the color and brightness of the paint.

Examples of Bases:

• Titanium Dioxide (TiO₂): A widely used base due to its high opacity and brightness, making it ideal for white and light-colored paints.
• Zinc Oxide (ZnO): Known for its anti-microbial and anti-corrosive properties, it is commonly used in protective coatings.
• Iron Oxide (Fe₂O₃): Used in paints for its durability and strong color, especially in red and brown shades.
• Lead Oxide (Pb₃O₄): Historically used for its durability and anti-corrosive properties, although its use has declined due to toxicity concerns.

Process of Application:

The base is mixed with other components of the paint, including the vehicle, driers, and extenders. The mixture is then applied to the surface in layers to achieve the desired finish. The base ensures the paint provides a smooth, opaque, and durable coating that adheres well to the substrate.

Explanation:

Stopping

• This is the correct term for filling nail holes, cracks, and small defects in wood using putty or filler before painting.

• Ensures a smooth surface finish.

Additional Information Caulking

• Refers to sealing joints or seams in structures (like between walls, windows, or pipes) to prevent water or air leakage.

• Commonly done using caulk or sealant, not putty.

 Blocking

• In construction, it often refers to placing short pieces of wood between framing members for support or fire-stopping.

• Not related to surface finishing or painting.

 Knotting

• A treatment applied to wooden surfaces (especially over knots) using knotting solution to prevent resin from oozing out and affecting the paint.

• Done before stopping and painting.

Explanation:

Priming Coat

• Purpose: The priming coat is the first coat of paint applied to a new or bare surface. Its main function is to seal the surface, fill pores, and provide a smooth, stable base for subsequent coats of paint.

• Usage: The primer helps with the adhesion of the finishing layers of paint by ensuring they bond properly to the surface. It also helps in protecting the material beneath (such as wood, metal, or drywall) from moisture, rust, or other external elements.

Additional Information Putty Coat

• Purpose: The putty coat is applied to fill small cracks, imperfections, and uneven surfaces. It helps in smoothing out the surface before painting.

• Usage: It is typically used on surfaces that require smoothing or filling before applying the primary paint. However, it is not the first coat of paint applied and does not provide adhesion for subsequent layers.

 Finishing Coat

• Purpose: The finishing coat is the final layer of paint applied to achieve the desired color, texture, and sheen. It provides the finished look and protects the surface.

• Usage: After the priming coat and undercoat, the finishing coat is applied to give the surface its final appearance and durability.

 Under Coat

• Purpose: The undercoat is applied after the priming coat and provides an additional layer of coverage to improve the paint finish and durability. It also helps to enhance the adhesion of the finishing coat.

• Usage: The undercoat is essential for improving the adhesion and coverage of the final paint layer, but it is not the first coat applied to a new surface.

Explanation:

Bases: 

• It is a principal constituent of paint.
• It also possesses the binding properties.
• It forms an opaque coating.
• It also reduces the shrinkage cracks in the film on drying.
• Commonly used bases for paints are white lead, red lead, zinc oxide, iron oxide, titanium white, aluminium powder and lithophone.
• Lead paint is suitable for painting iron and steel works, as it sticks to them well.
• White lead is most suitable for wood surfaces.
• However, it is affected by atmosphere action and hence should not be used as a final coat.
• While zinc forms a good base but is costly.
• Lithophone, which is a mixture of zinc sulphate and barytes, is cheap.

Explanation:

Vehicle or carrier:

The vehicle is the liquid substance that holds the ingredients of paint in liquid suspension. They are required mainly for two reasons:

• 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 paint so that they may stick or adhere to the surface.

List of the vehicle for paints:

Important Points

• Turpentine oil is used as a solvent in the paint.
• The function of the solvent is to make the paints thin so that it can be easily applied to the surface. It also helps the paint penetrate through the porous surfaces. 

Explanation:

Paints are applied in multiple coats and each coat has a specific function which is described below:

1. Primer:

It is the first coat of paint that is directly applied to the surface. its purpose is to wet the surface and to provide good adhesion for subsequently applied coats.

2. Intermediate Coats:

Intermediate coats are applied to build the desired thickness of the surface. These may two, three, or any no. of coats as required. Generally, the thicker the coating, the longer the life.

3. Finished Coat:

The finish coat provides the required appearance and surface resistance of the system. Depending on the conditions of exposure, it must also provide the first line of defense against weather and sunlight.

Explanation:

As per IS 15489 : 2004:

1. Maximum Surface drying time for class A and Class B type plastic emulsion paint is 45 minutes.
2. Maximum Surface drying time for class C and Class D type plastic emulsion paint is 90 minutes.
3. Maximum Hard drying time for class A and class B type plastic emulsion paint is 240 minutes.
4. Maximum Hard drying time for class C and class D type plastic emulsion paint is 480 minutes.

Concept:

“Blistering” is the formation of “bubbles” in the exterior decorative paint film, resulting from localised loss of adhesion and subsequent lifting of the existing paint film from the underlying surface. It may be that one paint layer has lost adhesion to the one beneath or it may be that all the paint layers collectively have lost adhesion to the underlying substrate. The loss of adhesion and blistering can quickly lead to paint flaking and peeling.

Two main types of blistering:

1. Those caused by moisture entrapment within the substrate beneath the paint film, which converts from a liquid into a vapour when the surface is heated by the sun and expands but cannot escape through the paint film. 
2. Those caused by solvent entrapment beneath the paint film during application, where the solvent cannot escape (evaporate) when the surface is heated up quickly.

Important Points

Some other defects in painting:

1) Blistering:

This defect is caused by the water vapor which is trapped behind the painted surface. The formation of bubbles under the film of paint occurs in this defect. It may occur from various causes such as imperfect seasoning of timber, excess oil used in the final coat.

2) Bloom:

In this defect, the formation of dull patches occurs on the finished polished surface. It is due to the defect in paint or bad ventilation.

3) Fading:

The gradual loss of colour is known as fading and it is mainly due to the effect of sunlight on pigments of paint.

4) Flaking:

A small portion of the painted surface is sometimes seen loose. It is known as flaking and it is due to poor adhesion.

5) Flashing:

sometimes the glossy patches are seen on the painted surface. This is known as the flashing and it is due to poor workmanship, cheap paint, or weather actions.

6)Wrinkling:

When a horizontal surface is too thickly painted, the defect is wrinkling becomes prominent.

Concept:

Paints:

• It is the mechanical dispersion of one or more fine pigments in a medium (thinner + vehicle). When the paint is applied to a metal surface, the thinner evaporates, while the vehicle undergoes slow oxidation leading to the formation of a pigmented film.

Constituents of paint:

1. Base: 

• It is a metallic oxide which is the principal constituent of a paint. It makes the paint film opaque & processes binding properties which reduce the shrinkage cracks in the film on drying.
• E.g- White lead, Red lead, Zinc oxide, Iron oxide, etc

2. Vehicle or drying oils: 

• It is a liquid that binds the pigment to the surface and protects pigment from decay e.g. linseed oil, dehydrated castor oil, etc.
• E.g- Linseed oil, Tung oil, Poppy oil, Nut oil, etc

3. Extenders or fillers: 

• The function of the addition of filler in paint is that it improves the properties of the paint and mainly reduces the cost. The main purpose is to increase pigment volume concentration.
• E.g- Gypsum, Calcium carbonate, Aluminium silicate, Magnesium silicate, Talc, Diatomite, etc

4. Thinners or solvents: 

• It is a volatile solvent, which is often added to paint which helps to adjust the consistency of the paint.
• Solvents of oil paints are used to thin the paints and increase the spread.
• E.g- Turpentine, White spirit, Naptha, Benzine, Petroleum, etc

5. Drier: 

• The main function of a drier is to increase the drying power of the vehicle. They act as oxygen-carrying catalysts.
• E.g- Litharge, Red lead, Sulphate of manganese, etc

6. Plasticizer: 

• They remain permanently in paints and varnishes.
• They improve the elasticity of the paint film which prevents cracking of the film.

Concept:

Paints:

• Paint is a substance used as the final finish to all surfaces and as a coating to protect or decorate the surface.
• Paint is a pigmented opaque material that completely covers and hides the surface to which it is applied.
• Paint is available in oil-based and water-based formulae.
• It is used as a protective coating and is normally sprayed/brushed on. Paint prevents corrosion.
• It is a combination of pigments with suitable thinners or oils to provide decorative and protective coatings.
• For different conditions, different types of paints may be useful. 

Plastic paint:

• Plastic paints contain plastic as the base.
• Plastic paints dry very quickly, provide a better appearance, and have high covering power. 
• This paint uses water as a thinner.

Varnish:

• Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials.
• Varnish is traditionally a combination of drying oil, a resin, and a thinner or solvent.
• Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of "flatting" agents.

Hence, S1 is false and S2 is true

Additional Information

Thinner:

Liquid thinner is added to the paint is as follows:

• To increase fluidity
• To make the paint more smooth
• To help penetration into porous surfaces

Concepts:

The common defects in paints are:

1. Blistering and Peeling:  Blistering and peeling are defects in which swelling of the paint film occurs caused by the formation of an air bubble under the paint film due to the presence of moisture or oil or grease matter. If it is due to moisture then it is called peeling and if it is due to oil and grease matter then it is called blistering.

2. Fading: Fading is the discoloration of the paint surface due to atmospheric agencies such as sunlight, and moisture.

3. Grinning: The visibility of the background due to insufficient opacity of paint film even after the final coat is called grinning.

4. Chalking: Chalking is the formation of powder on the painted surface. This is due to the use of insufficient oil in the primer.

5. Flaking: The detachment of paint film from the surface is called flaking. It occurs when the bond between surface and paint film is poor. 

6. Blooming: The formation of dull patches on a painted surface is called blooming  It is due to improper ventilation, weathering, defective paint, etc.

7. Bittiness: Bittiness is a condition in which small particles project above the surfaces of the film of paint or varnish yielding a rough surface. This may be due to dirty surfaces, dirty brushes, or a dirty atmosphere.

8. Bleeding: The diffusion of colored material into the upper coat from the undercoat.

Explanation:

Anticorrosive paint

• This paint essentially consists of oil and a strong drier.
• A pigment such as chromium oxide, lead, red lead or zinc chrome is taken and after mixing it with some quantity of very fine sand, it is added to the paint.

Asbestos paint

• This is a peculiar type of paint and it is applied on the surfaces which are exposed to acidic gases and steam.

Bituminous paint

• This paint is prepared by dissolving asphalt or mineral pitches or vegetable bitumen in any type of oil or petroleum.
• The paint presents a black appearance and it is used for painting ironwork underwater.

Oil paint

• This is the ordinary paint and it is generally applied in three coats of varying compositions.
• They are respectively termed primers, undercoats, and finishing coats.
• This paint is cheap and easy to apply and it possesses good opacity and low gloss.

Plastic paint

• This paint contains the necessary variety of plastics and it is available in the market under different trade names.
• The application of plastic paint can be done either by brush painting or spray painting.
• This paint possesses a pleasing appearance and is attractive in color.
• This paint is widely used for showrooms, auditoriums, etc.

Explanation:

Paints:

It is the mechanical dispersion of one or more fine pigments in a medium (thinner + vehicle). When the paint is applied to a metal surface, the thinner evaporates, while the vehicle undergoes slow oxidation leading to the formation of a pigmented film.

Constituents of paint:

1. Thinners or solvents: 

• It is a volatile solvent, which is often added to paint which helps to adjust the consistency of the paint.
• Solvents of oil paints are used to thin the paints and increase the spread.
• E.g- Turpentine, White spirit, Naptha, Benzine, Petroleum, etc

2. Vehicle or drying oils: 

• It is a liquid that binds the pigment to the surface and protects pigment from decay e.g. linseed oil, dehydrated castor oil, etc.
• E.g- Linseed oil, Tung oil, Poppy oil, Nut oil, etc

3. Extenders or fillers: 

• The function of the addition of filler in paint is that it improves the properties of the paint and mainly reduce the cost. The main purpose is to increase pigment volume concentration.
• E.g- Gypsum, Calcium carbonate, Aluminium silicate, Magnesium silicate, Talc, Diatomite, etc

4. Pigment: 

• It is an essential constituent of paint. It provides color and opacity, in addition to that imparting strength and aesthetic appeal to the paint.
• E.g- White lead, Red lead, Zinc oxide, Iron oxide, etc

5. Drier: 

• The main function of a drier is to increase the drying power of the vehicle. They act as oxygen-carrying catalysts.
• E.g- Litharge, Red lead, Sulphate of manganese, etc

6. Plasticizer: 

• They remain permanently in paints and varnishes. They improve the elasticity of the paint film which prevents cracking of the film.

7. Anti-skinning agents: 

• These are chemicals added to paints to prevent gelling and skinning of the film is called plasticizers.

Concept-

The usual defects which are found in the painting work are-

Blistering:

• This defect is caused by the water vapour which is trapped behind the painted surface. The formation of bubbles under the film of paint occurs in this defect. It may occur from various causes such as imperfect seasoning of timber, excess oil used in final coat etc.

Bloom:

• In this defect, the formation of dull patches occurs on the finished polished surface. It is due to the defect in paint or bad ventilation.

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 small portion of the painted surface is sometimes seen loose. It is known as the flaking and is due to poor adhesion.

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 seen. This is known as the grinning.

Running:

• The paint runs back and leaves small areas of surface uncovered. This defect occurs when the surface to be painted is too smooth.

Sagging:

• When a vertical or inclined surface is too thickly painted, the defect of sagging occurs.

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:

• When a horizontal surface is too thickly painted, the defect of wrinkling becomes prominent.