Light Fastness and Storage Fading: Protecting Colour on Display
Colour that fades on a shop display or a sunny shelf is a warranty risk, and light fastness testing is the only reliable predictor.
The following sections cover the definition, the specification values, production control, testing and commercial impact.
Test principle
Samples are exposed to controlled xenon arc or carbon arc light alongside blue wool standards and graded for fading.
Because it touches comfort, appearance and durability at the same time, it is worth planning deliberately.
Blue wool scale
Grades run from one to eight, with five or better usually required for apparel and six to seven for automotive or outdoor use.
Include the requirement in the purchase order, because that is the document both parties rely on commercially.
- Request test reports on production fabric, not on development samples
- Verify the sampling plan and the number of specimens
- Store reports with roll or lot identification for traceability
Fibre and dye influence
Basic dyes on nylon and pale fluorescent shades are the classic weak points.
Escalate deviations immediately, as a small change early in the run is cheap to correct and costly to fix later.
Storage fading
Phenolic yellowing and nitrogen oxide fading during storage are separate phenomena requiring specific tests.
Repeat the test when the fabric, the mill or the finishing route changes, as previous results no longer apply.
- Agree tolerances in writing before the first sample is made
- Define the measurement condition and the direction measured
- Review the limit each season against real performance data
Practical actions
Specify light fastness in the dye recipe brief, and test the finished fabric rather than the yarn or greige.
Choose suppliers who understand the requirement, because competence reduces the hidden cost of rework.
Summary
The technical content is straightforward. The discipline lies in writing it down, testing it on production fabric and repeating the result on the next order.
