Colour Fastness Explained: The Grey Scale, the Tests, and What to Spec

Colour fastness is a garment's resistance to losing colour - by fading, or by bleeding onto something else - when it meets the everyday agents it will face: washing, rubbing, light, sweat and water. It is one of the few quality properties a customer notices directly (a top that pinks the white sofa, jeans that rub off on a bag), and it is one every tech pack should state as a number, not a hope. Here is how it is measured and what to write down.

How fastness is graded: the two grey scales

Fastness is not pass/fail - it is a rating from 1 to 5, read against a standard grey scale under controlled light. Two separate scales are used:

• Grey scale for colour change - rates how much the test fabric itself shifted. 5 = no change, 1 = severe change.
• Grey scale for staining - rates how much colour transferred onto an adjacent white fabric. 5 = no staining, 1 = heavy staining.

Half-steps (4-5, 3-4, …) are normal. Most buyers set a minimum acceptable grade per test; anything below it fails the shipment. A typical commercial floor is grade 3-4 for wash and rubbing, but always defer to the buyer's standard.