Light-sensitive papers as controls for testing textile colorfastness and stability of materials under arc lamp exposure

Abstract

A simple method of control of the integrated exposure of the fluctuating arc lamps used in the textile and other industries for testing lightfastness of textile dyeings and stability toward light of materials in general, is described. A piece of light-sensitive paper is placed in lamps along with materials to be tested, and the exposure is terminated when a match with a standard, observable with the unaided eye, is obtained. The standard is a strip of the same batch of paper that has been exposed in a master lamp to a definite light dosage. The method is based upon standard light quantities and is thus largely independent of variation between batches of light-sensitive paper. The variations among fading lamps used in the textile industry and the causes, such as differences in lamp models, and line voltage, are discussed. A 4-percent difference in line voltage leads to a difference in radiant output of 11 percent in the waveband from 300 to 480 millimicrons, the region probably causing most of the fading of dyed textiles. Variations in line voltage considerably larger than 4 percent are probable in many communities. The papers were made in batches of 20 to 30 thousand test pieces by dip-dyeing special cotton-rag or wood-fibers papers with aqueous solutions of Niagara Blue G, or with Victoria Blue B in aqueous ethanol. One paper was made by beater-dyeing wood fibers with Niagara Blue G to give a nonleaching paper and was sized with melamine resin to impart high wet strength, making the paper suitable for lamps with water spray. Other paper-dye combinations were studied. Data are presented indicating the visual sensitivity of the various types of papers from 1 to 100 hours of usual arc exposure, the permanence of the papers during storage in the dark, the uniformity throughout each batch, and the effect of nonuniformity, temperature effect, lasting qualities of the standard strips during use, correlation with textile dyeings, and the effect of intermittent exposure. The master lamp used for standardizing the papers, its accessories, and reproducibility of input power and radiant output are discussed.