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Fading of artificial hair color has been investigated by simulating actual usage conditions through exposure to artificial radiation in a weatherometer, with 0.35 mW/(m(2) nm) at 340 nm, for 16 to 48 hours, and by periodical washing. Hair color was produced by using commercial two-part, permanent hair dyes with light auburn, medium auburn, and dark auburn shades. Formulations based on red couplers, such as 4-amino-2-hydroxytoluene and 1-naphtol, as well as primary intermediates, such as 1-hydroxyethyl-4,5-diamino pyrazole sulfate, were employed. Results indicate that the extent of fading, as measured by the total color change parameter, dE, is greatest for colored hair subjected to both irradiation and shampooing, and significantly smaller for hair undergoing only irradiation or washing. Color loss has been also found to be dependent upon the hair type employed, with colored natural white and bleached hair undergoing much greater change than colored brown hair. It has been also shown that hair color based on pyrazole intermediates displayed the deepest fading as a result of shampooing (dE approximately 4-6 after ten shampooings) and irradiation/shampooing (dE approximately 14-16 after 32 hours of light exposure and four shampooings). The contribution of UV light (UVB + UVA) to the artificial hair-color loss was found experimentally to be dependent upon the irradiation dose and varied from 63% at 16 hours of irradiation time to 27% at 48 hours of light exposure. The theoretical extent of photoprotection by a formulation was assessed by calculating the percentage of UV light it attenuates in the wavelength range from 290 nm to 400 nm. The results indicate that UVB photofilters, such as octyl methoxy cinnamate, absorb less than 25% of the total UV irradiation at concentrations as high as 30 mg/(g hair). UVA absorbers were found to be more effective, with benzophenone-3 and benzophenone-4 absorbing about 40% of UV at the same concentration. Corresponding experimental data were in reasonable agreement with the theoretical predictions. The data are also presented for color protection with treatments containing two photo-absorbers: benzophenone-3-ZnO; benzophenone-4-ZnO; octyl methoxy cinnamate-ZnO; and dimethylpabaimidopropyl laurdimonium tosylate-benzophenone-3. |
