92 JOURNAL OF COSMETIC SCIENCE (a) (b) ß ! ! i I I 1 O0 Ixm 100 pm Figure 3. Further magnified views of a single fiber in Figure 2. Parts a and b correspond to the respective notations in Figure 2. (a) (b) : i : 1 50 I•m 50 I•m Figure 4. SEM images of cross sections of hair fibers: (a) without and (b) with white lines at the fiber center (a) ' (b) ' ! ! [ I mm I mm Figure 5. Reflecting optical microscopic views of hair fibers: (a) from untreated dark hair and (b) from bleached hair. GONIOPHOTOMETRIC MEASUREMENT Figures 6a and 6b show the reflection intensity curves of two hair tresses observed at 400 nm (open circles) and 700 nm (closed circles), with less (Figure 6a) and more (Figure 6b) porous medulla. These two hair tresses were from different origins and prepared under the same bleaching conditions (bleaching agent: 3.4% H202/0.67% NH3 agent/hair = 1/1 by weight, treated at 30øC for 20 min). In the case of few medulla pores (Figure 6a), the reflection curve at 700 nm (closed circles) shows two peaks. The main peak around 40 degrees is specular reflection from

MEDULLA STRUCTURE AND HAIR APPEARANCE 93 (a) 0.5 0.4 0.2 0.1 0.0 0 20 40 60 80 Receiving Angle / degree (b) 0.5 0.4 0.3 0.2 0.1 0.0 0 20 40 60 80 Receiving Angle / degree Figure 6. Goniophotograms for hairs with (a) lesser and (b) greater amounts of porous medulla ar 400 and 700 nm wavelength. Open circle: at 400 nm. Closed circle: at 700 nm. the front surface, and the second peak around 55 degrees is the reflection from the backside surface of the hair fibers (11,12). On the other hand, the reflection curve at 400 nm (open circles) shows only a single peak around 40 degrees. This difference in the reflective properties can be understood through the light absorption behavior of melanin granules. Because melanin granules absorb light with a shorter wavelength than light