Overview
If your sofa is not in the darkroom of an establishment, it is permanently exposed to light. The UV component of the light is responsible for the fading and decomposition of the upholstery fabric. Areas that are exposed to sunlight change their appearance significantly after some time. The colors of the sofa fabric fade.
Lightfastness is determined by the wool scale (grades 1-8) or by the assignment of stars (classification system from 0 to 5 stars).
The wool scale – the DIN measuring method
To determine the degree of lightfastness via the wool scale, the sample material, together with eight wool strips, is exposed to UV light. The wool strips are each dyed with blue dye in different light fastness.
To perform the test, a part of each of the wool strips and the test fabric is covered, i.e. not irradiated with UV light.
When the wool strip with the most lightfast coloration starts to fade, the test is stopped and the sample is used for comparison. Depending on which wool strip is closest to the degree of fading of the sample, the lightfastness is determined.
Light fastness according to wool scale
| Level according to wool scale | Rating | Days* |
|---|---|---|
| 8 | excellent | 700 |
| 7 | superb | 350 |
| 6 | very good | 160 |
| 5 | good | 80 |
| 4 | pretty good | 40 |
| 3 | moderate | 20 |
| 2 | low | 10 |
| 1 | very low | 5 |
* Number of days a fabric is exposed to the sun outdoors in Central Europe before a color change occurs.
Classification by stars
Another system divides the lightfastness of cover fabrics into six different classes. Here, five stars are awarded for the highest lightfastness and zero stars for very low lightfastness.
Light fastness in stars
| Level in stars | Corresponds to wool scale | Rating |
|---|---|---|
| 5 Stars | Level 8 | very high lightfast |
| 4 Stars | Level 7 | high lightfast |
| 3 Stars | Level 5-6 | lightfast |
| 2 Stars | Level 4 | limited lightfast |
| 1 Stars | Level 3 | low lightfast |
| 0 Stars | Level 1-2 | volatile |
Color fastness of upholstery fabrics
Rub fastness (also abrasion resistance according to the Martindale method), perspiration fastness, saliva fastness, wash fastness and bleach resistance provide information about the color fastness of a fabric.
