Correct Answer: D. priming coat
Solution:
The priming coat, or primer, is the foundational layer applied to a bare surface. Its primary roles are to seal the substrate (filling pores) and to create a surface that subsequent coats of paint can adhere to effectively.
Correct Answer: A. 45
Solution:
According to Indian Standard IS 15489, for Class A (premium quality) plastic emulsion paints, the surface should be dry-to-touch within a maximum of 45 minutes under standard conditions.
Correct Answer: D. Turpentine oil
Solution:
The vehicle consists of the binder (which forms the film) and the solvent. Linseed, tung, and poppy oils are drying oils that act as binders. Turpentine oil, however, is a solvent or thinner; it dissolves the binder to make the paint workable but evaporates and does not form part of the final paint film.
Correct Answer: B. Blistering
Solution:
Blistering is the paint defect characterized by the formation of bubbles or blisters on the surface. It is typically caused by trapped moisture or solvent vaporizing and pushing the paint film away from the substrate.
Correct Answer: D. Red lead
Solution:
Red lead is a traditional and effective anti-corrosive primer for iron and steel surfaces that are exposed to the atmosphere. It provides a protective barrier against rust. It should not be used on steel that will be embedded in concrete, as it can react with the cement.
Correct Answer: A. Manganese
Solution:
Lead-based driers can sometimes react with certain pigments, causing discoloration. To counteract this, a small amount of another metallic drier is used. Sulphate of manganese acts as an effective co-drier that helps stabilize the paint and prevent discoloration issues associated with lead driers in zinc-based paints.
Correct Answer: B. Flaking
Solution:
Flaking is the paint defect where small portions of the paint film become detached from the substrate due to a loss of adhesion. This results in loose pieces or flakes of paint on the surface.
Correct Answer: D. Grinning
Solution:
Grinning (or grin-through) is a defect where the underlying surface or previous coat of paint is visible through the final coat. This happens when the topcoat has insufficient opacity or hiding power, or when it has been applied too thinly.
Correct Answer: B. Running
Solution:
If a surface is too smooth or glossy, the new coat of paint may not have enough "tooth" to adhere to properly. This can lead to the paint flowing downwards under gravity, creating drips or curtains. This defect is known as running or sagging.
Correct Answer: D. Rosin
Solution:
Boiled linseed oil acts as a vehicle (binder and part of the solvent system) in oil paints and varnishes. It is an effective solvent for natural resins like rosin (colophony), which is often used to make simple, inexpensive varnishes.
Correct Answer: B. Varnish
Solution:
This is the definition of varnish. It is a transparent coating made by dissolving a resin in a specific solvent (like alcohol, oil, or turpentine). When applied, the solvent evaporates, leaving the resin behind as a protective film.
Correct Answer: D. Drier
Solution:
A drier is a metallic salt (e.g., lead acetate, manganese sulphate) added in small quantities to oil-based varnishes and paints to act as a catalyst, speeding up the oxidation and polymerization process that causes the oil to harden or "dry".
Correct Answer: A. Oil Varnish
Solution:
Oil varnishes cure to a hard, durable, and water-resistant finish, making them ideal for surfaces that are exposed to wear, weather, and require frequent cleaning, such as doors, windows, and outdoor furniture.
Correct Answer: B. Spirit
Solution:
French polish is made by dissolving shellac resin in alcohol. Since alcohol is a type of spirit, French polish belongs to the spirit class of varnishes.
Correct Answer: C. POP
Solution:
POP (Plaster of Paris) is often applied over plastered walls in a thin layer (a skim coat) to fill minor imperfections and create a perfectly smooth, level surface that is ideal for receiving high-quality paints.