Performance Guidelines Physical test
Colour fastness to light
Light fastness relates to the ability of a
textile to retain its colour under the influence
of light. When testing for light fastness, the
samples are illuminated using artificial
daylight for a specified period. Together with
the samples, a so-called blue scale is also
illuminated. The blue scale consists of eight
standard textiles of known light fastness. In
the evaluation, the fading of the samples is
compared with the fading on the blue scale.
The evaluation scale ranges from 1 to 8, with
8 being the best value. An increase of one
point corresponds to a doubling of the light
fastness, i.e. the same fading takes twice as
long our minimum requirement is 5, and we
endeavour to ensure that all our materials
fulfil this requirement. In some cases,
however – e.g. pastel colours and un-dyed
items – that can be difficult to achieve.