SUNLIGHT AND PRETREATED HAIR 81 COLOR MEASUREMENT The hair color was determined in Datacolor © 3890 equipment using the CIELAB- system. TENSILE STRENGTH TESTS The breaking tenacity and breaking elongation were measured ten times on ten indi- vidually irradiated hairs in an Instron 1122 © apparatus. The test was carried out wet, in distilled water, using a gauge length of 10 mm, a test speed of 10 mm/min, and a preload of 10 N. LIPID DETERMINATION The extraction of surface lipids and internal lipids (IL), thin-layer chromatographic separation, and quantitative determination of cholesterol were carried out as described earlier (3) RESULTS AND DISCUSSION COLOR CHANGES For the assessment of color changes induced by irradiation of cosmetically treated hair, changes in brightness (AL*) and the color coordinates on the red green axis (Aa*) and the blue yellow axis (Ab*) were determined after two and four weeks of irradiation according to the CIELAB system. These results are compared in Table I. A difference of 1.5 units is significant. UV-B and IR irradiation did not cause a significant color change, whereas UV-A and VIS showed a considerable influence on the hair samples. Therefore, their resulting brightness and yellow values are represented graphically as a function of irradiation time and are discussed below. Brightening and color changes caused by sunlight occur linearly both in untreated and cosmetically treated hair with the exception of chemically bleached samples (see below). UV-A irradiateduntreated and permed hair shows after four weeks of irradiation no significant change in brightness hair dyed red increases in brightness after this period of time by 4.5 units and bleached hair by 9 units (Figure 1). VIS irradiated hair shows a considerably higher extent of bleaching than that irradiated with UV-A (Figure 2). Already after two weeks a significant brightening is visible both in cosmetically pretreated and untreated hair, which is further increased by another two weeks of irradiation. Chemically bleached hair brightens after four weeks of irradiation with visible light by 25.8 units, dyed hair by 10.8 units, permed hair by 6.8 units, and untreated hair by 3.9 units. Untreated and cosmetically treated hair becomes significantly more yellow after four weeks of irradiation with UV-A (Ab* is positive in Figure 3). Chemically bleached (Ab* = 5.7) and dyed samples (Ab* = 5.9) become considerably more yellow during this period of time than untreated (Ab* = 1.8) or permed hairs (Ab* = 2.2).

82 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Change of Color Values on the Brightness (AL), Red Green (Aa), and Blue Yellow (Ab) Axes of Untreated and Cosmetically Treated Human Hair After Irradiation With Individual Parts of Sunlight for Four Weeks Irradiation time 2 Weeks 4 Weeks Range of Treatment irradiation AL Aa Ab AL Aa Ab Untreated UV-B 0.3 0.3 0.2 0.6 0.5 0.5 Permed UV-B 0.4 0.2 0.4 0 0.3 0.4 Bleached UV-B 0.7 0.2 0.4 1.0 0.3 0.9 Dyed UV-B 0.5 0.4 0.7 0.3 0.7 1.3 Untreated UV-A 0.5 0.6 0.8 1.3 1.3 1.8 Permed UV-A 0.6 0.8 1.1 1.0 1.5 2.2 Bleached UV-A 4.0 0.6 3.4 8.2 0.7 5.7 Dyed UV-A 2.0 1.6 2.8 4.4 2.8 5.9 Untreated VIS 1.4 1.4 2.0 3.9 2.8 4.5 Permed VIS 2.5 2.1 3.2 6.8 3.9 7.6 Bleached VIS 15.6 1.2 5.7 2 5.8 3.8 6.1 Dyed VIS 5.0 2.5 6.4 10.8 4.1 12.4 Untreated IR 0.2 0.2 0.2 0.1 0.2 0.3 Perreed IR 0.6 0.3 0.2 0.5 0.4 0.5 Bleached IR 0.9 0.2 0.1 1.4 0.2 0.1 Dyed IR 0.5 0.3 0.6 0.8 0.5 1.1 6- 2- 0- •n bteoched • •m dyed •, *'•" • e•, - • ....- -' unfreafed -•.•'--' - .............. 8 permed o 2 Irrodiofion time in weeks Figure 1. Increase in lightness of untreated, permed, dyed, and bleached human hair after irradiation with UV-A. Treatment for four weeks with visible light (Figure 4) leads tO stronger yellowing than with UV-A. Untreated, permed, and bleached hairs show values for Ab* of 4.5-7.6 units, and dyed hair becomes more yellow by 12.4 units. VIS caused a visible change on the red green axis after irradiation for four weeks (Table