Characteristic: Colour Fastness MCQs Quiz | Class 9
This quiz is for Class IX students studying Home Science (Code 064), focusing on Unit V: Fibre and Fabric. This specific quiz covers the topic of Colour Fastness, including key concepts like resistance to fading and bleeding. Attempt all questions and click ‘Submit Quiz’ to see your score. You can then download a PDF of your answers for revision.
Understanding Colour Fastness in Fabrics
Colour fastness is a crucial property of a textile, indicating how well its colour resists fading or running when exposed to various conditions. A fabric with good colour fastness will retain its original hue through washing, exposure to sunlight, rubbing, and perspiration. This is important for the longevity and appearance of our clothes and home furnishings.
Key Concepts: Fading and Bleeding
Two common problems related to poor colour fastness are fading and bleeding.
- Colour Fading: This is the gradual loss of colour from a fabric. The most common cause is exposure to sunlight (UV radiation), which breaks down the chemical bonds in dyes. Other factors include harsh detergents, high-heat washing or drying, and atmospheric contaminants.
- Colour Bleeding: This occurs when excess dye is not properly fixed to the fabric fibres and washes out, potentially staining other clothes in the same wash load. It is often seen in new, brightly coloured garments, especially with hot water.
Factors Influencing Colour Fastness
Several factors determine how well a fabric holds its colour:
| Factor | Impact on Colour Fastness |
|---|---|
| Type of Dye | Synthetic dyes like vat and reactive dyes are generally more fast than natural dyes. |
| Type of Fibre | Some fibres bond with dyes better than others. For example, polyester is dyed with disperse dyes that are very fast. |
| Mordants | These are chemical substances used to fix dyes on fabrics, significantly improving colour fastness. |
| Washing Method | Using cold water, mild detergents, and gentle cycles helps preserve colour. |
| Sunlight Exposure | Direct and prolonged exposure to sunlight is a primary cause of fading. |
Quick Revision Points
- Colour fastness measures a fabric’s ability to resist colour loss.
- Fading is colour loss, often due to sunlight.
- Bleeding is when dye washes out of a fabric.
- “Crocking” is the term for colour transfer due to rubbing.
- Check care labels for washing instructions to maintain colour.
- Washing new, dark-coloured items separately can prevent bleeding onto other clothes.
Extra Practice Questions
- What is the primary environmental factor that causes fabric colour to fade?
- Explain the difference between colour bleeding and crocking.
- Why is it recommended to wash dark and light coloured clothes separately?
- What role does a mordant play in the dyeing process?
- How can you test a new garment for colour fastness at home before washing it with other items?
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