Photobleaching of Wool Regardless of Yellowness Cause

Abstract

Light was found to bleach wool that had yellowed from a wide variety of causes. The spectrum of the bleaching light and, to a lesser extent, the chemistry of the pigment determine the rate. For rapid bleaching, light should contain no uv below 360 mμ, and preferably no uv at all, as this causes competitive yellowing. Photobleaching of wool previously exposed to uv at 254 mμ was found to be some 20,000 times faster than spontaneous dark bleaching (or reversion).