Trim Light Fastness and Fading Guide

A hang tag goes pale after three weeks in a shop window, a woven label sample fades after a summer on the windowsill, a paper bag loses its colour after a few months by the door. Fading of garment trims is far more common than most teams assume. Colourfastness to light measures how well a material resists fading under daylight and artificial light, and it is a completely different property from fastness to washing or to rubbing. Most complaints of the “it survived the wash but changed in store” kind trace back to light fastness.

1. Separate the Four Causes of Fading First

Changing supplier at the first sight of fading rarely solves anything. The four causes behave differently, are tested differently and are fixed differently.

• Photodegradation of dyes: dyes in yarn and tape break down under UV and visible light, and moisture plus heat accelerate it clearly. Fabric that looks worn after sun exposure while losing only a little depth is usually this type.
• Ageing of pigments and inks: organic pigments used in offset, screen and digital printing differ hugely in light fastness. Blues, magenta, pinks and fluorescents are the most sensitive — they lighten first and the whole tag then looks grey.
• Yellowing of lamination and varnish: the resin base of matte or gloss film and UV varnish yellows under UV, showing up as “not faded, but yellowed and tired”. Poor varnish shows within three months.
• Optical brighteners and dye migration: fluorescent whitening agents in paper and pale yarn fail first, turning white to cream; dyes in dark wrapping paper or dark tape can also migrate into adjacent pale fabric when damp. Both are often misread as a printer cutting corners.

2. How Light Fastness Is Measured: Three Common Standards

The core of a light fastness test is a yardstick: reference standards whose fading rate is known. The same sample placed by a window for a month in a southern summer and a month in a northern winter gives two different results, so the work belongs in a lab with a controlled light source, recorded by radiant exposure rather than by hours.

Two details cause most of the confusion. First, the scales differ: a European grade 4 is generally stricter than an American grade 4, so agree on the system before quoting. Second, a report must state the radiant exposure (usually in kJ/m²) and the light source used for grading, otherwise “20 hours” is not comparable between machines. Most apparel brands ask trims to reach grade 3–4 or above, and dark or highly saturated colours often need a separately agreed minimum.

3. Light Fastness by Trim Type

4. Reducing Fading Risk at the Design and Sourcing Stage

• Limit high-risk hues: magenta, fluorescent yellow and orange, and bright violet generally have the lowest ceilings. If a brand colour must be used, reduce its area, move it to a spot colour with a protective coat, and run a window simulation early.
• Let the material be the background: kraft paper for the tag, or a black background actually woven from dyed yarn rather than printed, removes one fading layer. Full-bleed dark printing is where fading complaints concentrate.
• Choose a non-yellowing protective coat: matte lamination beats bare print for light fastness, but the film or varnish itself must be a non-yellowing grade — essential on pale and white backgrounds.
• Fix the display side too: switching window spots to low-UV LED, adding shading or a backing panel behind the sample clearly extends display life. It is why most brands rotate window samples every four to six weeks.

5. Writing Light Fastness into the Spec and the Inspection

• State four things: the standard, the minimum grade, the radiant exposure and the grading light source. “Light fastness OK” is not a requirement.
• Agree who submits the sample and who pays. The usual split is the supplier submitting and paying on first development, with annual re-testing or material changes negotiated case by case; costs depend on the lab and the test scope, so confirm before ordering.
• Keep and log reference samples: one physical sample per material, colour and ink system, with batch and date. When a complaint arrives, re-test the retained sample first and discuss liability afterwards.
• Require notice of changes: a new ink brand, a new paper, a new yarn supplier can all shift light fastness even when the appearance matches. Putting “changes require re-confirmation” in the order terms is the cheapest protection.

6. Five Common Misconceptions

• Confusing light fastness with wash fastness: passing a wash test says nothing about a window, so keep both reports.
• Assuming darker is safer: dark shades carry a higher dye load and often fade more, it is simply harder to see at a glance.
• Treating lamination as double protection: film blocks UV but can yellow itself; use a non-yellowing grade on pale products and keep a comparison sample.
• Testing only the hang tag: on the same style, bags and cords generate fading complaints at least as often as the tag itself.
• Judging fading from phone photos: auto white balance corrects the fading away. Compare against a retained sample under a defined light source, or grade to the standard.

Related Articles

• Trims FAQ: all articles
• Woven Label Colourfastness Guide: Washing, Rubbing and Bleeding
• Hang Tag Ink Safety Guide: Migration, Odour and Compliance
• Hang Tag Colour Management: Proofing, Matching and Batch Consistency