What is lightfastness?
Colour stability of outdoor fabrics explained
Lightfastness describes how well a fabric colour withstands sunlight. It is tested to ISO 105-B02 and rated on an eight-step scale, where 1 is the lowest and 8 the highest lightfastness. This page explains what the rating actually tells you, what it does not tell you, and which value suits your application.
What lightfastness actually measures
Sunlight carries a high share of UV radiation, and UV attacks dyes. How much a fabric changes colour as a result is determined in a laboratory under controlled conditions. Four points explain the method.
A comparison, not a stopwatch
The fabric sample and a blue wool scale are exposed together, each partly covered. The difference between the exposed and the covered area is then assessed. The rating names the blue wool reference that behaved in the same way.
The blue scale is a textile
It is not an instrument but a strip of blue wool threads dyed to defined standards that fade at different rates. It is exposed alongside the sample and serves as the reference.
The scale doubles, but only by design
The eight steps are geometric by design: step 2 is intended to be twice as lightfast as step 1, step 3 twice as lightfast as step 2, and so on. The gap between 7 and 8 is therefore far larger than the gap between 1 and 2. The word by design matters: a peer-reviewed study by Ford and Korenberg (Studies in Conservation, 2023) shows that commercially available blue wool standards do not necessarily follow this rule in practice, because manufacturing batches vary. The rating is meant for orientation, not for calculation.
Two standards, one scale
ISO 105-B02 tests against artificial light from a xenon arc lamp that simulates daylight. ISO 105-B01 tests the same property against real daylight. The rating scale is identical in both cases.
The eight lightfastness ratings
Lightfastness is the branch of colour fastness that deals with light. The rating is always given relative to the scale and written as a fraction, for example 7-8/8. The denominator is the maximum of the scale, not a number of years.
| Rating | Meaning | Suitable for |
|---|---|---|
| 8 | outstanding | premium outdoor, best rating available |
| 7 | excellent | permanent outdoor use over several years |
| 6 | very good | outdoor use with a service life of years |
| 5 | good | seasonal outdoor use, bright interiors |
| 4 | moderate | interiors with daylight, short outdoor use |
| 3 | moderate to low | interiors with little daylight |
| 2 | low | interiors with little daylight |
| 1 | very low | not suitable for textiles exposed to light |
Two common misunderstandings
A lightfastness of 7/8 does not mean a fabric survives a set number of hours in the sun. It means the fabric behaved like blue wool reference number 7. How many real hours of sunshine that translates into depends on location, climate and installation, and cannot be derived from the rating alone. The American AATCC system makes this especially clear: it measures exposure in fading units, which are independent of time. Twenty fading units are not twenty hours. The AATCC states explicitly that light exposure is not measured in hours or days.
The blue scale carries the scale on which lightfastness is reported. The grey scale is the tool used to assess the degree of colour change. There is no red wool scale for lightfastness testing. Anyone asking for one usually means one of these two.
Why solution-dyed fabrics achieve higher ratings
Lightfastness is not determined by the fibre type alone but above all by how the colour gets into the fibre. There are two fundamentally different routes.
Solution-dyed: colour in the fibre core
The pigments are added to the liquid polymer before the fibre is extruded through the spinneret. The pigment therefore sits in the core of the fibre. UV light reaches it less easily, and even as the surface wears, the same colour lies underneath.
Conventionally dyed: colour on the fibre
Here the finished yarn or fabric is immersed in a dye bath, so the colour sits on the surface. Such fabrics generally reach lower ratings than solution-dyed ones and are very well suited to seasonal use.
Lighter shades usually rate higher
Within one collection, different colours reach different values. This is why lightfastness is often quoted as a range, for example 4-6/8. Vivid and very bright shades are more sensitive than pale or very dark ones.
No fabric is immune to UV
Even the best rating does not mean the colour lasts forever. It means a visible change occurs much later. Covering or storing cushions when they are not in use noticeably extends how long the colours stay fresh.
Lightfastness of our fabrics to ISO 105-B02
All values are taken from the manufacturers' technical data sheets. A range indicates that the colours within one collection perform differently.
| Fabric | Lightfastness | Dyeing method |
|---|---|---|
| Agora Air | 7-8/8 | solution-dyed |
| Agora Liso | 7-8/8 | solution-dyed |
| Agora Panama | 7-8/8 | solution-dyed |
| Agora Lines | 7-8/8 | solution-dyed |
| Agora Rayure | 7-8/8 | solution-dyed |
| Agora Liso Waterproof | 7-8/8 | solution-dyed, laminated |
| Agora Life Liso | 7/8 | solution-dyed, recycled |
| Agora Life Panama | 7/8 | solution-dyed, recycled |
| Agora Life Wabi | 7/8 | solution-dyed, recycled |
| Polysun | 7-8/8 | solution-dyed |
| Olefin | 7/8 or higher | solution-dyed |
| Livorno screen fabric | 7/8 or higher | 100% polyester |
| Cover PVC | 7-8/8 | PVC-coated polyester, UV-stabilised |
| Dralon Acrisol Liso | 4-6/8 | conventionally dyed |
Which rating do you actually need?
A higher value is not automatically the right one. What matters is how long and how directly the fabric is exposed to the sun. These four cases cover most situations.
Seasonal outdoor use, stored in winter
In use from April to September, then stored dry: a rating of 5-6/8 is enough here. Dralon suits this rhythm well and offers a particularly wide choice of colours.
Permanently installed outdoors
Awnings, shade sails, fixed shading and applications near water should be at 7-8/8. The solution-dyed Agora fabrics cover this range.
Indoors at a south-facing window
Curtains and cushions in direct sunlight through glass are under more strain than most people expect. A rating of 5-7/8 makes sense here.
Indoors with little light
Sofa cushions in the living room, seat pads in the dining room, scatter cushions away from the window: a rating of 4-5/8 is sufficient for these.
Frequently Asked Questions
Sources
- Ford, B.; Korenberg, C. (2023): Manufacturing Variations in ISO Blue Wool Fading Standards under Microfading Exposure Conditions. Studies in Conservation (peer-reviewed, DOI 10.1080/00393630.2023.2184555), free author copy
- AATCC (American Association of Textile Chemists and Colorists): Blue Wool Lightfastness Standard Updates, on time-independent measurement in fading units
- FEB (German association of resilient floor covering manufacturers): UV lightfastness, blue scale and grey scale in the test method
- All fabrics at Germes
- Germes guides
Last reviewed: 21.08.2026 · Reviewer: Germes-Team
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