Colorfast
Standard — one of 3 in the glossary
A measure of how well a dyed fabric holds its colour against washing, rubbing, perspiration and sunlight. It is not a yes or no property: mills test each of those separately and rate them, and a fabric can be colourfast to laundering but poor to light. It matters commercially because a customer judges a decorated garment by how it looks after a month, not on delivery. It also matters technically on dark polyester, where dye that is not fast under heat migrates out of the fabric and stains the print — the reason low-bleed inks and blocker underbases exist.
Not one property
Mills test colourfastness separately against washing, rubbing, perspiration, light and sometimes chlorine, and rate each on its own scale — commonly one to five.
A fabric can be excellent to laundering and poor to light, which is exactly the combination that produces a shirt that survives the wash and fades on a shop rail.
So "colourfast" without a qualifier says very little. The useful question is fast to what.
What each test is about
Washing: whether colour is lost from the fabric or transfers onto other garments in the load. This is the one behind a dye-catcher sheet.
Crocking, or rubbing: whether colour comes off on skin or on a car seat, dry or wet. Dark denim is the familiar failure.
Perspiration and light: whether sweat or UV breaks the dye down over time.
Each has its own standard test, so a spec sheet that gives a single number is summarising.
Where it bites on a decorated garment
The customer judges a printed shirt by how it looks after a month, not on delivery. A fabric that loses colour makes a good print look bad.
On dark polyester it matters technically as well as commercially: dye that is not fast under heat migrates out of the fabric and stains the ink. That is why low-bleed inks and blocker underbases exist.
If a job is going somewhere sunny or somewhere sweaty — outdoor events, sports kit — ask about light and perspiration fastness specifically rather than accepting a general claim.
Common questions
- What does colorfast mean?
- That a dyed fabric holds its colour under a particular stress — washing, rubbing, perspiration or light. Each is tested and rated separately, so a fabric can be fast to one and poor to another.
- What is crocking?
- Colour rubbing off a fabric onto skin or another surface, tested both dry and wet. Dark denim marking a light car seat is the everyday example.
- Why does dye migration matter on printed shirts?
- Because dye that is not fast under heat moves out of the fabric and into the ink, turning a white print on a dark polyester shirt pink or grey days after it left the press.
Where this comes up
See also
Last reviewed