Correlation of Visual Luster with Measured Reflectance of Cotton Fabrics

Abstract

A group of 20 white fabrics and 12 blue fabrics, that were carefully constructed from specially prepared cotton yarns to produce fabrics of varying degrees of luster were used in this study. Some of each group were chemically modified with dimethylolethyleneurea and some of these resin-treated fabrics were calendered to produce fabrics of high luster. These fabrics were rated by a panel and the consensus of visual luster rankings was compared with ranking of luster obtained by measurements of specular and disuse re flectances. Reflectances were measured with both the Photovolt Reflection and Glossmeter and the Farrand Spectrofluorometer modified as a reflectometer. The latter instrument was used to hieasure reflectance of both polarized and unpolarized light. Consideration has been given to angle of incidence and reflectance, peak intensities, areas under re flectance curves, depolarization techniques, size of sample irradiated, and treatment of combinations of specular and diffuse reflectance data in the correlation of measured luster and visual luster indices. Use of polarized light was slightly advantageous when used with blue fabrics. While various treatments of reflectance data obtained with both instruments yielded agreement of approximately 75% between instrument and panel con sensus, the best correlation (82%) was obtained by ranking fabrics according to the ratio of specular to diffuse reflectances as measured with the Photovolt instrument.