How fabric behaves
Colourfastness
Colourfastness is a set of separate properties rather than one. A fabric can hold colour perfectly in washing and transfer it onto a white shirt when rubbed, or survive both and fade in sunlight. Each behaviour has its own test, its own grade and its own relevance depending on what the garment does.
Contents
Colour problems often reach the customer, because they appear in use rather than at inspection. A dark polo that marks a white collar, a sports top that fades along the shoulders, a black apron that transfers onto a chef's jacket: none of these are visible when the goods are packed, and all of them are testable before production.
The four tests that matter for apparel
| Property | Standard | What it simulates | When it matters most |
|---|---|---|---|
| Fastness to washing | ISO 105-C06 | Domestic and commercial laundering with a reference detergent | Everything that is washed, and especially uniform and workwear programmes |
| Fastness to rubbing | ISO 105-X12 | Colour rubbing off onto another material, tested dry and wet | Dark and saturated shades, denim, anything worn against light clothing |
| Fastness to perspiration | ISO 105-E04 | Contact with acidic and alkaline solutions representing sweat | Sportswear, workwear and anything worn during exertion |
| Fastness to light | ISO 105-B02 | Exposure to a xenon arc light source | Outdoor garments, and anything displayed in a window or worn in strong sun |
Rubbing fastness, sometimes called crocking, is one buyers often underestimate. It is tested both dry and wet, and the wet result is usually the weaker of the two, which is why colour transfer complaints often come from garments worn in warm weather. How a colourfastness result feeds a care instruction is covered in materials, trims and care instructions.
How results are expressed
Results are graded visually against grey scales. Change in the colour of the specimen itself is assessed against the scale described in ISO 105-A02, which runs from grade 5 for no perceptible change to grade 1 for severe change, with half steps between. Staining of an adjacent white fabric is assessed against a separate staining scale.
That is why a colourfastness requirement is normally written as two numbers: one for shade change and one for staining. A specification that asks only for good colourfastness is not a specification, because it cannot be passed or failed.
What decides the result
- Fibre and dye class. Cotton is normally dyed with reactive dyes and polyester with disperse dyes, and the two behave differently. Disperse dyes in particular can move under heat, which is a separate problem covered in colour change on polyester.
- Depth of shade. Deep and saturated colours carry more dye, and more dye means more available to transfer. Black, red and royal blue are the classic risk shades for rubbing.
- Dyeing and washing-off. Unfixed dye left on the fibre surface after dyeing is a common cause of poor rubbing results, and it is a process control issue at the dye house.
- Finishing. Softeners and other surface treatments can affect fastness results in both directions.
- Blends. A fabric with two fibre types is dyed with two dye systems, and one of them may be the weaker link.
What to specify, by product
| Product | Tests worth specifying |
|---|---|
| Everyday retail garments | Washing and rubbing, dry and wet |
| Uniform and workwear programmes | Washing at the actual laundering temperature, plus rubbing and perspiration |
| Sportswear and teamwear | Washing, perspiration and light, since all three are met regularly |
| Dark and saturated shades | Rubbing given priority, with the wet result stated explicitly |
| Outdoor and display products | Light fastness in addition to the usual set |
| Products with a light component against a dark one | Staining assessed specifically, since transfer between components is the risk |
Where this connects to production
Colourfastness is a property of the dyed fabric, so it is established at fabric approval rather than at garment inspection. Two practical points follow. The test should be run on the actual production fabric and shade, not on a similar colour from the same quality, because depth of shade changes the result. And the retained approved lab dip is the reference the production fabric is judged against, which is the same physical standard used for shade assessment, described in the colour matching guide.
Where a delivery has already been rejected for colour, the assessment method matters as much as the result. Judging shade and staining under uncontrolled light produces disagreements rather than answers, as covered in why fabric shade varies between dye lots.
Questions buyers ask about this fabric
What is colourfastness?
The resistance of a dyed textile to losing or transferring colour under a specific condition: washing, rubbing, perspiration or light. Each condition is a separate property with its own test, so a fabric can perform well in one and poorly in another.
Why does a new dark garment mark other clothing?
That is poor rubbing fastness, usually caused by unfixed dye left on the fibre surface after dyeing. It is tested dry and wet under ISO 105-X12, and the wet result is normally weaker. Deep shades carry the highest risk, so specify the test for dark colours.
How are colourfastness results reported?
As grades against grey scales, normally from 5 for no perceptible change down to 1 for severe change, with separate grades for the shade change of the specimen and for staining of an adjacent white fabric. A requirement should state both.
Which colourfastness tests do we actually need?
Washing and rubbing as the baseline. Add perspiration for sportswear and workwear, and light fastness for outdoor or displayed products. Specify the test at the temperature and conditions the garment will really face rather than a default.
Is colourfastness the same as shade matching?
No. Shade matching is whether the fabric is the right colour to begin with. Colourfastness is whether it keeps that colour and keeps it to itself. A fabric can match the approved standard perfectly and still fail a rubbing test.
Specifying colour requirements for a programme?
Tell us the shade, the fabric and how the garments will be washed and worn. We will confirm which tests are relevant, run them on the production fabric and report the grades before bulk.
Discuss colour testing
