---
title: "Defects in paints"
subject: "Civil Engineering Materials"
chapter: 9
key: "semester_3/civil_engineering_materials:defects-in-paints"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/defects-in-paints
site: BCT Engineering
---

# Defects in paints

Civil Engineering Materials · Chapter 9: Paint and Varnishes

- Asked in: 2078 Bhadra, 2 marks
- Video: [Types Of Defects In Paints, its Causes and Remedies |Defects In Painting](https://www.youtube.com/watch?v=MPcZLqR7A1k) — Civillogy (Study of Civil Engineering)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/defects-in-paints
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-9

## Question

Explain any four defects in paints.

## Short answer

Blistering is bubbling from trapped moisture or damp substrate. Flaking/peeling results from poor preparation or dampness. Cracking and crazing appear from ageing or a hard coat over a soft one. Chalking is a powdery surface from binder decay under sun. Fading is colour loss from sunlight or chemical action.

## Answer

Common defects in paint work:

1. **Blistering:** Bubbles in the film caused by moisture or gas trapped under the paint, or by painting on a damp surface.
2. **Flaking (peeling):** Paint comes off in flakes because of poor surface preparation or dampness.
3. **Cracking and crazing:** Fine cracks caused by ageing, unequal drying rates, or a hard coat applied over a soft one.
4. **Chalking:** A powdery surface caused by decay of the binder under sun and weather.
5. **Fading:** Loss of colour due to sunlight or chemical action.
6. **Sagging (running):** Paint flows down in curtains when it is applied too thickly or has been thinned too much.
7. **Wrinkling:** The top surface dries and forms a skin before the paint below it has dried, so the film wrinkles.
8. **Bloom and grinning:** A dull, cloudy film (bloom), or the earlier coat showing through because of poor covering power (grinning).

## Check yourself

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

1. What causes blistering of paint?
   A. Too many coats of primer
   B. Sunlight fading
   C. Moisture or gas trapped under the paint
   D. Thin paint
   Answer: C. Moisture or gas trapped under the film, or painting on a damp surface, forms bubbles. (Key point: Blistering)

2. What is chalking?
   A. Paint flowing in curtains
   B. Powdery surface from binder decay by sun and weather
   C. Colour loss only
   D. Surface skin forming
   Answer: B. Chalking is a powdery surface from decay of the binder by sun and weather. (Key point: Chalking)

3. Sagging (running) occurs when paint is applied how?
   A. Too thick or too thin
   B. On a hot dry surface only
   C. With a dirty brush
   D. In the dark
   Answer: A. Paint applied too thick or too thin flows down in curtains. (Key point: Sagging)

4. What commonly causes flaking (peeling)?
   A. Good preparation
   B. Poor surface preparation or dampness
   C. Too much drier
   D. Fading
   Answer: B. Poor surface preparation or dampness makes paint come off in flakes. (Key point: Flaking)

## Related in Civil Engineering Materials

- [Defects caused by seasoning](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aseasoning-defects-timber) — Civil Engineering Materials, chapter 7

## Related in other subjects

- [Common acoustic defects](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aacoustic-defects) — Building Technology, chapter 1
- [Solidification, shrinkage and casting defects](https://www.bctengineer.com/question.md?key=semester_4%2Fmanufacturing_and_production_processes%3Asolidification-shrinkage-casting-defects) — Manufacturing and Production Processes, chapter 4