Natural white hair Bleached hair FADING OF ARTIFICIAL HMR COlOR dE = 1.8 8.] dE = L7 4.5 Dark brown hair -p dE = O J , . •- -� I•- ... -1 415 u Vi,gm·e • . Color loss for �amples dyed dar · r d after ten shampooings or 32 hours of irradiation, with ,.,:ashing after every eight hours of exposure (irradiation). include the absorbance curves of hair subjected to ten shampooings and to 3 2 hours of irradiation/sl ampooing combination treatments. Dyed natural white and bleached hair exhibir- maximum ab or ance of approxi, atdy l.5-L6 near 500 nm, \vhich declines above 5 50 nm. · leachcc hair is characterize by greater : bs rbance above 600 nm, lea ling to che d rker app·arance of the s-u11ples tr ated wit.h a hair color. Based on the ab orbance �pecrra it is e id 11t that oly n smt 11 pero.:ntage of rhe dye is rel o cd .1 a result of sham po ing alon , fi r b th rypes of hair. Combimtion crcatmenrs (irradiati 1 / shampooing) lead m a greater los of col r for the nau ral whice and bleached h· ir. ] n contrast to this, as demonstrated by resulc not shown here, dyed dark hro\l n h. ir had a maximum absorbance of approxim rely 1.6, with a smaller decrease in abs rhance above 600 nm. The absorbance of the dark brown sampl s at 700 11m \Va!'. -1, with little change � frer shampooing or irradiation. Figure 6a shows images of natural white (Piedmont) hair dyed with a medium auburn dye (II, non-pyrazole) and exposed to 16 and 32 hours of irradiation. One set of samples was shampooed after every eight hour of irradiation, while the other \\as irradiated with no shampooing. All tresses h, d sections that \Vere not exposed to light, and their color loss is thought to e related to elevated temperature and humidity during irradiation. As in tile experimen described in the preceding paragraph, dyed hair samples expos d to both irradiation and shampooing lost noticeably more colo than samples that were only irradiarecl or slnmpooed (Figure 6b). The a erage total color changes for areas of the samples shampo eel but nor expo eel rn irradiation :vere 1.1 and l.5 after 16 and 32 hours of irradiation, which corresponc s to two and four shampooings, respectivdy. For areas exposed to irradiation but not shampooed the ·oral color changes were 3.3 and 7.5

416 JOURNAL OF COSMETIC SCIENCE Cl) u C C'IJ CD u C C'IJ -e 0 Cl) .Cl ct 2�-----------------------------. a: Natural White Hair 32 Hours irradiation with 4 washings 0 +------,-------.----------.---------.----------,--------, 400 450 500 550 Wavelength (nm) 600 650 700 2.00 �------------------------------ b: Bleached Hair Irradiated 32 hours with 4 washings -f 1.00 +-----------------------+---....::,,.,.=---�..-----, 0 Cl) .Cl ct 0.00 -l-------------------------------- 400 450 500 550 Wavelength (nm) 600 650 700 Figure 5. Absorbance spectra of natural white (a) and bleached (b) hair before and after dyeing, and after ten washings or 32 hours of irradiation, with washing every eight hours.