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Effect of Light upon Wool: Part I: Greening and Yellowing by “Germicidal” Ultraviolet
- Launer, Herbert F.
- air, color, direct contact, irradiation, lamps, lipid content, ozone, photochemical reactions, radiant energy, reflectance, solvents, spectroscopy, temperature, textile fibers, water content, wool, woolen fabric
- Radiant energy from “Germicidal” lamps, consisting of 89% of ultraviolet at 253.7 mμ, caused undyed wool fabrics to become strongly greenish-yellow in air of normal moisture content. Comparative reflectance and absorption measurements indicate that the color is due to the production by this ultraviolet of probably two or more substances that absorb in the violet-blue and in the orange regions. The violet-blue absorber, which accounts for the yellowness, increased with time and temperature of irradiation. The orange (together with the violet-blue) absorber accounts for the greenness; it varied with time and temperature and reached a maximum in 45 min (direct contact with lamp). Greening was not evident under 2.5 min or over 10 hr. Both absorbers were produced in dark reactions that follow the initial photochemical reactions, as shown by the effect of temperature, which was greater for the orange absorber. The rate of formation of both absorbers, but especially the orange, was decreased by even moderately impeding the flow of air to the wool during irradiation. Ozone was not involved. Tristimulus and Munsell color values are given for comparison in one case. The effects of ultraviolet were practically indistinguishable for 6.1-oz flannel purified with solvents and for tropical worsted and 4.7-oz flannel of normal grease and oil content.