1.1 ,This practice covers a method for exposing specimens of colored art materials indoors to sunlight coming through a closed window. A card containing eight Blue Wool References2 is exposed simultaneously. Blue Wool References2 3, 6, and 7, are used as controls in determining when to remove test specimens from exposure and rate them. Test specimens are rated by assigning each specimen the number of the Blue Wool Reference that shows the same amount of color change.