Spectrophotometric Measurement of Color in Wool Fabrics

Abstract

A method is described for measuring the differential absorption spectra of pale- colored fine-wool fabrics in the visible and ultraviolet regions. A strip of the fabric is immersed in a liquid having a refractive index close to that of wool and compared in an ultraviolet spectrophotometer with a similarly immersed uncolored or bleached strip of the same fabric. The method is applied to the measurement of the absorption spectra of normal un bleached wool fabrics and to fabrics which have been yellowed either by heating at 97° C. in an aqueous buffer solution at pH 8 or by exposure to ultraviolet irradiation. Fabrics which have been dyed or treated with reagents producing colored derivatives of particular amino acid residues in the wool proteins have also been tested. Sizing and finishing agents in the fabric which absorb in the visible or ultraviolet regions are detected by the method. When wool is yellowed by heating or exposing to ultraviolet irradiation, its absorp tion increases far more in the ultraviolet region of the spectrum, especially at 3100-3300 Å, than in the visible region above 3900 A.