PHOTOLIGHTENING MECHANISM OF RED HAIR 49 were prepared. The tresses were washed three times with aqueous sodium laureth sulfate solution (15%), adjusted to pH 7 with phosphoric acid, and air dried. TREATMENT OF RED HAIR WITH PAP AIN Red hair (50 g) was treated with papain to obtain brown granules. The treatment method was performed according to Zahn's method for the isolation of melanin granules (15). Crude granules (500 mg) isolated from the 50 g of red hair were washed twice with a hexane/isopropanol/water (6/6/1) mixture (200 g), and further washed three times with deionized water (200 ml) to purify them prior to drying under reduced pressure (10 cmHg, at 60°C, for 1 hr). The SEM image of the obtained granules is shown in Figure la. For comparison, the SEM image of the eumelanin granules isolated in the same way from Chinese black hair is shown in Figure 1 b. The granules obtained from the red hair were mainly of indeterminate form, with sizes of around 0.4 µm, which coincides with published data for pheomelanin granules (16). A small amount of rice-like granules, which are considered to be eumelanin granules, was also observed. IRRADIATION EXPERIMENTS Irradiation experiments were carried out with a solar simulator and some optical filters, under the same conditions as previously reported (1). VIS-light (wavelength 370-780 nm) and UV-light (wavelength 280-400 nm) intensities were representative of those found in natural sunlight. In this work, for each light irradiation experiment, one irradiation unit corresponds to a single light exposure in sunlight for one hour. Ir­ radiation was performed under dry conditions, between 25° and 35°C, and at 20- 30% RH. LIGHT IRRADIATION ON RED HAIR Red hair tresses were irradiated with VIS or UV light in the two cases detailed below. For each condition, six tresses were taken and their data averaged. Case 1: Irradiation with repeated washing. The hair tresses were washed at specific irra­ diation times (5-20 irradiation units) with aqueous sodium laureth sulfate solution (15%), adjusted to pH7 with phosphoric acid, rinsed, and then air dried. Thereafter, the color was measured and irradiation was carried out. a b Figure 1. Isolated granules through papain treatment. a: From red hair. b: From black hair.

50 JOURNAL OF COSMETIC SCIENCE Case 2: Irradiation without washing. The hair tresses remained unwashed throughout. The color was measured at identical irradiation times to those in Case 1. IRRADIATION OF GRANULES OBTAINED FROM RED HAIR In order to accurately measure the color, granules were fixed in a silicone film using the following method: Granules (40 mg) were dispersed in hexane (3g)/dimethypolysiloxane (Silicone SH-200C, 1,000,000 cs Toray Dow Corning Silicone, Tokyo, Japan) (0.6 g), after which 0.2 g of the dispersion was poured into a petri dish (I 16 mm) and left overnight to remove all the hexane and leave the granules in the silicone film. Nine samples were prepared. Three of the samples were kept shielded from light, three addi­ tional samples were irradiated with VIS light, and the final three samples were irradiated with UV light. The color of the irradiated samples was measured after each irradiation period, and it was found there was no color change of the shielded samples after the experimental period. IRRADIATION OF RED HAIR CROSS SECTIONS Three red hair fibers were fixed between two plastic plates and cut with an ultramicro­ tome to expose the hair cross sections in the way described in the previous paper (1). Twelve samples were prepared in this manner and divided into three groups. Four of the samples were shielded from light, an additional four samples had cross sections irradiated with VIS light, and the final four samples had cross sections irradiated with UV light. Irradiation of the cross sections was carried out for 20 irradiation units. Two samples from each group were gently shaken in deionized water (100 ml) for 30 seconds. The cross sections from both washed and unwashed samples were observed using SEM (magnification: x 7,000). Ten SEM images were taken for each unwashed sample, and the number of melanin granules, together with the number of cavities where melanin granules had run out, were then counted. The percentage of melanin granules that disappeared was defined as: Percentage of disappeared melanin granules = Number of cavities I (Number of cavities + Number of granules) x 100 In those cases where only a partial solid remained in a cavity, it was counted as one granule. In order to ensure the data were reliable, over 1000 cavities and granules for each experimental condition were counted. Percentages were calculated for each image and then averaged. COLOR MEASUREMENT The lightness (L) values of the samples were measured using a chromameter CR-300 (Minolta Co., Ltd., Osaka, Japan), according to the CIELAB system (illuminant C, 2° standard observer). The lightening degree (� L) was calculated as follows: �L = Lt - L0 where L0 is the L value of the untreated sample and Lt is the value of the treated sample.