388 JOURNAL OF COSMETIC SCIENCE expected, every hair became lighter after exposure. This change was more pronounced when UVB was cut out of the radiation system. Blond hair showed the greatest change, followed by white and dark-brown hair, respectively. Figure 2 shows the average results obtained for the yellow-blue difference parameter (Db*). Blond hair turns yellower after UV exposure, but not after UVB filtered radiation exposure. Dark-brown hair turns yellow after both UV and UVB filtered radiation exposure. Surprisingly, white hair turns less yellow after both UV and UVB filtered radiation exposure. Figure 3 shows the average results obtained for the red-green difference parameter (Da*). Dark-brown hair became redder after both exposure conditions. Blond and white hair showed an opposite trend, turning less red. Figure 4 shows the total color variation (DE*) obtained to the different hair type. Blond hair showed the greatest change, with DE* values on the order of 6.0 and 20.0 after 16 and 64 days of exposure, respectively. Total color difference values of about 3.0 for dark-brown and 10.0 for white hair were measured after exposure. Results show that hair color changes are mainly affected by UVA radiation in every hair type. According to Borges et al. (13 ), the total amount of melanin (eumelanin + pheomelanin) in blond and red hairs is about 2.5 mg/g hair, in dark-brown hair 5.2 mg/g hair and in black hair 7.2 mg/g hair. As expected, we observe that the hair color change increased with the decrease in melanin content. On the other hand, the observation of color changes on white hair (without melanin) after irradiation shows that the melanin type and content of each hair is not the only parameter related to hair damage caused by sun exposure. Keratin is also photosensitive. Among the keratin amino acids, tryptophan, cystine, tyrosine and histidine are more susceptible to photo-degradation. The total amount of these amino acids depends on hair type. Male hairs have more cystine than female and, usually, dark hairs have more cystine than light hairs (8). According to Bertazzo et al. (14), the amount of tryptophan in dark-brown and black hair is greater than in blond hair. The highest trypthophan concentration is found in gray and white hair, indicating that tryptophan concentration in hair increases with age. Vincenci et al. White hair Blond hair Dark-brown hair -1 ·c: -3 -5 -7 -9 16 16 64 64 16 64 days days days days days days Figure 2. Average values of the yellow-blue difference parameter (Db*) for white, blond and dark-brown hair obtained after 16 and 64 days of simulated sun exposure, considering 4 h exposure per day. Ten color measurements on each sample. UV exposed._) UVA exposed. Unexposed.

2006 TRI/PRINCETON CONFERENCE 2--,----------�--------��--------� White hair Blond hair -4 -5 �--------�--------��--------� 16 64 16 days 64 days 16 days 64 days days days 389 Figure 3. Average values of the red-green difference parameter (Da*) obtained for white, blond and dark-brown hair after 16 and 64 days of simulated sun exposure, considering 4 h exposure per day. Ten color measurements on each sample. UV exposed. [] UVA exposed. ■ Unexposed. White hair Blond hair Dark-brown hair ;­ 20 5 15 +I CII � 10 0 � 5 16 days 64 days 16 days 64 days days 64 days Figure 4. Average values of the total color difference parameter (DE*) for white, blond and dark-brown hair obtained after 16 and 64 days of simulated sun exposure, considering 4 h exposure per day. Ten color measurements on each sample. UV exposed. UVA exposed. ■ Unexposed. (15) studied red hair, observing that the amounts of pheomelanin and eumelanin vary with sex, age and color shade. In this way, it must be assumed that color changes are related not only to melanin photodegradation but also to protein photodegradation, in a way that is difficult to account by now. MECHANICAL PROPERTIES Figures 5 and 6 show, respectively, the breaking strength and breaking elongation data