Faber-Castell uses the Blue Wool standard to evaluate lightfastness. This standard utilizes eight scales to evaluate lightfast colors and it has been used for Artist paints for many years. It is tested under museum conditions.
The Blue Wool test standard is comparable to ASTM D 5383-02 and ASTM D5383-97.
The Blue Wool standard relates to our star icons as follows:
*** = 7, 8 Blue Wool Scale
** = 5, 6 Blue Wool Scale
* = 3, 4 Blue Wool Scale
Prismacolor, Derwent and Van Gogh have embraced a new lightfastness standard developed in conjunction with The Color Pencil Society. This standard is called ASTM D 6901. This standard is not as precise as the Blue Wool method and only has two scales to evaluate lightfast colors.
It relates to our star icons as follows: I = ***, II = ** and *.