If you have a wool carpet that loses color just few days after its installation, it may be due to defective wool. In addition to color loss, you may also see white streaks or lines. The wool new, may have a luster to it. This defect has to do with hollow regions inside the filament. These hollow regions are called modulation. If the wool can not be dyed, then it is said to be variegated.
Modulated fibers do not have sufficient dye sites to hold dark colors. Whereas this carpet has been dyed with dark colors, they have likely crocked at this point.
A test for medulated woolen fibers is to soak them in a solution of 69% oil of
aniseed and 31% benzyl alcohol. This solution has a light refractive index of
1.576; wool is 1.548. Thus, non-medulated fiber will become invisible; medulated
ones will become white. The degree of medullation will be proportional to its
degree of whiteness. The container needs to be black to show the contrast.
The picture below shows remnant on a five day old installed piece in an elevator.
