Light fastness test:
Color fastness is the resistance of a material to
change any of its color characteristics or extent of
transfer of it’s colorants to adjacent white materials in
touch. It is a term used in the dyeing of textiles materials,
meaning resistance of the material’s color to fading or
running. In general, cloths should be tested for color
fastness before using bleach or other cleaning products.
Fastness tests establish the fitness for purpose of the
fabric and help identify the appropriate care label
instructions. Color fastness is a measure of two different
properties of a textile, the degree to which it changes
color when subjected to a particular treatment or
environment, and the tendency for the textile to cause
staining of other fabrics with which it comes into contact.
The color fastness properties of a textile will be related to
the type of fibers present, the construction of the
material, and especially to the type of dyestuff used and
the method by which it has been applied. Fastness
properties depend on the strength of the attractive forces
between the dyes and the fiber. Light fastness, wash
fastness and rub fastnesses that are standardized. The
light fastness of textile dye is categorized from one to
eight. The higher the number the better fastness is
obtained.