HAIR BREAKAGE DURING COMBING AND BRUSHING 635 Table III Length of Comb Stroke and Hair Breakage Average length of comb stroke No. of short breaks No. of long breaks LIS 8.9 cm 107 15.5 0.15 15.2 cm 120 21.3 0.18 RH = 60 ± 5%. Each number is an average of two or more replicas. 22.9 cm 249 105.5 0.42 Short-versus-long effect significant at the p = 0.02 level. Comb stroke effect significant at the p = 0.02 level. The ratios are significant at the p = 0.003 level. No. of short breaks No. of long breaks LIS Table IV Curvature and Its Effect on Hair Breakage Straight hair (C = 3 .14*) 39.5 6.5 0.19 RH = 60 ± 5%. Each number is an average of two replicas. Medium-curl hair (C = 6.77*) 324.5 204 0.63 * Curvature (C) was determined by the method of Robbins and Reich (5). Curvature effect, p = 0.0001. Short-versus-long effect, p = 0.017. Combing Brushing Table V Combing Versus Brushing and the LIS Ratio Non-bleached hair 0.18 2.16 Bleached hair 0.34 3.47 Brushing versus combing, p = 0.0001, highly significant. Non-bleached versus bleached, p = 0.05, sig­ nificant. dramatic change in the ratio. This is because the brush creates more looping of hairs over other hairs higher up in the tress and less end wrapping since the brush bristles are further apart than comb teeth and end wrapping does not occur as readily in the brush, producing fewer short segment breaks. Furthermore, the multiple columns and rows of bristles tend to create more looping of hairs higher up in the tress, providing more long segment breaks. Furthermore, the brush tends to distribute the hair over a wider area as compared to a comb, which tends to confine the hairs to a more narrow area. Thus the comb produces more end wrapping. CONCLUSIONS Hair breakage by brushing has some parallels with combing, but some differences also. Brushing provides a higher ratio of long-to-short segment breaks because the brush creates more looping of hairs over other hairs higher up in the tress, thus producing more long segment breaks. Less end wrapping occurs, with brushing producing fewer short

636 JOURNAL OF COSMETIC SCIENCE segment breaks. The ratio of long-to-short segment breaks is a good way to follow the effect of different variables on the types of hair breakage that occur under different conditions. Variables such as bleaching, a longer comb stroke, increasing fiber curvature, wet combing versus dry combing, and brushing versus combing all provide for an increase in long segment breaks and an increase in the LIS, with the largest effect produced by brushing. REFERENCES (1) C. Robbins, Hair breakage during combing. I. Pathways of breakage,]. Cosmet. Sci., 57, 233-243 (2006). (2) A. C. Brown and J. A. Swift, Hair breakage: The scanning electron microscope as a diagnostic tool,]. Soc. Cosmet. Chem., 26, 289-299 (1975). (3) C. Robbins, Hair breakage during combing. II. Impact loading and hair breakage,]. Cosmet. Sci., 57, 245-257 (2006). (4) C. Robbins and Y. K. Karnath, Hair Breakage during combing. III. The effects of bleaching and conditioning on short and long segment breakage by wet and dry combing of tresses,]. Cosmet. Sci., 58, 477-484 (2007). (Presented in part at the 2nd International TRI/Princeton Conference on Applied Hair Science, September 18-19, 2006.) (5) C. Robbins, Chemical and Physical Behavior of Human Hair, 4th ed. (Springer-Verlag, New York, 2002), pp. 432-433.