Tested under museum conditions, 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. 8 is the level of the highest lightfastness. 

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 *.