The hair shape of Japanese people is generally categorized as straight. On the other hand, most of Japanese women have concern about their hair appearance caused by curvature of the hair. The state and relationship of hair shape and appearance in Japanese women has been investigated.
Two hundred and thirty Japanese woman volunteers, aged from 10 to 70 years, were randomly selected and the curl radii of ten fibers from each volunteer were measured. Hair appearance of those volunteers was photographed under constant lighting conditions and hair style and hair luster were evaluated by hair stylists and researchers. Hair luster index was determined by the image analysis of the photographs. Then, the relation ship between the hair appearance and curl radius was analyzed.
The evaluation of hair style revealed that 53 % of Japanese women volunteers have straight hair as natural style, while the remaining 47 % have curved hair style (slightly wavy, wavy or frizzy style). The average curl radius of the women hair was determined to be 4.4 ± 2.3 cm and ranged from 0.6 to 16 cm. The mean curl radius of each hair style was confirmed as following order; straight > slightly wavy > wavy ~ frizzy. It was found that the hair with high curvature tended to show lower luster, and that hair luster of each volunteer correlated with the mean curl radius of the hair. In addition, there were slight inverse correlation between curl radius and volunteer’s age.
It was concluded that approximately half of Japanese women had curved hair, and hair luster was affected by hair fiber shape. These results suggest that microstructural analysis of curved hair may be important to solve hair concern caused by curved hair shape.