---
title: "Ingredients of paint and their role"
subject: "Civil Engineering Materials"
chapter: 9
key: "semester_3/civil_engineering_materials:ingredients-of-paint"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/ingredients-of-paint
site: BCT Engineering
---

# Ingredients of paint and their role

Civil Engineering Materials · Chapter 9: Paint and Varnishes

- Asked in: 2081 Baisakh (new course), 3 marks; 2081 Chaitra (new course), 2 marks; 2080 Baisakh, 3 marks; 2076 Asoj, 2 marks; 2074 Chaitra, 2 marks (asked 5 times)
- Video: [Components of Paints](https://www.youtube.com/watch?v=kyjYsKfEz88) — Engineering Motive
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/ingredients-of-paint
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-9

## Question

What are the different ingredients of paint? Explain their role as ingredients of paint.

## Short answer

Paint contains base, vehicle, pigment, drier, thinner and sometimes extenders. The base provides body and opacity; the vehicle binds and forms a film; pigment gives colour; drier speeds drying; thinner aids application.

## Answer

Paint is a mixture of a **base**, **vehicle**, **pigment**, **drier**, **thinner** and sometimes extenders, in liquid form. When applied, the thinner evaporates, the vehicle dries and a hard coloured film remains.

1. **Base:** The main solid that forms the body of the paint and gives opacity. It fills pores and gives a uniform surface. Examples: white lead, zinc white, titanium white, red lead, iron oxide, aluminium powder.
2. **Vehicle (carrier):** A liquid, usually a drying oil (linseed, tung, poppy oil) that holds the base and pigment, spreads them and binds them to the surface on drying. It forms the tough film and gives durability and gloss.
3. **Pigment:** A fine colouring powder that gives the colour and also helps resist weathering (e.g. lamp black, chrome yellow, Prussian blue, red oxide, ultramarine). It also gives some opacity.
4. **Drier:** Added (about 8% by weight of oil) to speed up oxidation and hardening of the oil. Examples: litharge, red lead, manganese dioxide, cobalt compounds.
5. **Thinner (solvent):** Added to make the paint thin enough to spread and to dissolve the vehicle; it evaporates after application. Examples: turpentine, mineral spirit, naphtha.
6. **Extender/adulterant (optional):** Cheap inert filler such as barytes, gypsum, china clay, which adds bulk and reduces cost.

**Ready mixed paint** contains all of these in a can and needs only stirring and thinning before use.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. The vehicle in paint is:
   A. A coloured powder
   B. A drying oil that holds and binds base and pigment into a tough film
   C. A solvent that evaporates
   D. A filler
   Answer: B. Linseed or tung oil forms the film on drying. (Key point: Vehicle)

2. The role of the drier is to:
   A. Add colour
   B. Thin the paint
   C. Speed up oxidation and hardening of the oil
   D. Add bulk
   Answer: C. Driers such as litharge and cobalt compounds speed drying. (Key point: Drier)

3. The thinner:
   A. Makes paint spread by dissolving the vehicle and then evaporates
   B. Stays in the film
   C. Gives colour
   D. Hardens the film
   Answer: A. Turpentine or mineral spirit evaporates after application. (Key point: Thinner)

4. Which is correct?
   A. Pigment gives colour; extender is a cheap inert filler like barytes that reduces cost
   B. Pigment is a thinner
   C. Extender speeds drying
   D. Pigment is the vehicle
   Answer: A. Extenders add bulk and lower cost. (Key point: Pigment and extender)

## Related in other subjects

- [Ingredients of an oil bound paint](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aoil-paint-ingredients) — Building Technology, chapter 9
- [Paints, oil paint ingredients, painting woodwork](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apaints-characteristics-066bh) — Building Technology, chapter 9