Studies in Wool Yellowing

Abstract

Equipment is described which is suitable for irradiating small samples of fabric or solution with high-intensity uv light of known wavelength. A 1000-watt mercury vapor lamp and a 1600-watt xenon arc have been used in such equipment to irradiate fine wool fabric with consecutive 20 m μ bands covering the wavelength range 250-410 m μ. With both sources the "yellowness index" and "apparent thiol" concentration were found to increase with decrease in wavelength, while the concentrations of cystine and trypto phan decreased. In experiments with the xenon arc, tyrosine and, to a lesser extent, methionine and histidine were also partly destroyed. Doubling the exposure signifi cantly increased the destruction of cystine but not yellowing or destruction of other amino acids. The changes in amino acid concentration were relatively slight compared with yellowing of the fabric, and it is suggested that the effects may have been restricted mainly to the surface layers of the exposed fibers.