Question

In testing the colour fastness of a dye, Crock meter is used. If the dye has best wash fastness, the grade will be

• A. 3
• B. 5
• C. 2
• D. 1

Hint:

• Crockmeter} tests colour fastness to rubbing.
• Wash fastness} tests colour resistance to washing.
• Most color fastness properties (rubbing, washing, perspiration, etc.) are graded using Grey Scales, typically from 1 (poor) to 5 (excellent/best).
• Grade 5 represents no change or no staining, indicating the best possible fastness.
• Grade 1 represents a very significant change or staining, indicating the poorest fastness.

Answer 1

The Correct Option is B

To understand this question, let’s break it down:

1. Crock Meter:

A Crock meter is a device used to test the color fastness to rubbing (also called "crocking") of dyed or printed fabrics. It assesses how well a dye resists being transferred to another surface through friction.

2. Wash Fastness:

Wash fastness refers to the resistance of dyed or printed fabric to washing, particularly the ability of the fabric to retain its original color without fading or bleeding during laundering.

Although the Crock meter tests color fastness to rubbing, in textile testing, fastness grades generally follow a standard scale from 1 to 5, where:

• Grade 1 = Poor fastness
• Grade 2 = Fair
• Grade 3 = Moderate
• Grade 4 = Good
• Grade 5 = Excellent fastness

3. Best Wash Fastness:

When the question asks about the best wash fastness grade, it refers to the highest level of resistance to washing — which is Grade 5.

Final Answer:

(2) 5 — This represents the best (highest) wash fastness grade.