The natural fluorescence of wool

Wool exhibits a natural fluorescence which increases markedly during irradiation. The tips of weathered wool fluoresce more strongly than the roots. Lambswool, which is weathered only slightly, shows only a weak fluorescence, although it has been found that a high intrinsic fluorescence of wool is not only caused by exposure to light. A direct correlation between yellowness and intensity of fluorescence exists. During photobleaching of initially yellow wool a decrease in fluorescence has been found, which reverses upon longer exposure to light.