634 JOURNAL OF COSMETIC SCIENCE combing, but some differences too. For example, the primary similarity is that brushing appears to produce breakage by hair loops forming around bristles and other hairs, with the primary breakage resulting from hairs looped around other hairs and stressed or impacted against other hairs as in combing. However, from a quantitative aspect, hair breakage by brushing produces more long segment breaks and fewer short segment breaks for the reasons explained above. In our previous work (4) we showed the effect of wet-versus-dry combing, summarized in Table II. The data from this study show that wet combing reduces short segment breakage and increases long segment breakage and thereby increases LIS. This effect occurs because wet hair provides clumping of hairs near the ends and therefore inhibits end wrapping and short segment breakage. We next decided to examine the effect of the length of the comb stroke on LIS. The data from this experiment are summarized in Table III and show an increase in both short and long segment breaks with increasing comb stroke. These effects result from more loop­ ing higher in the tress and also more end wrapping. Also the LIS ratio increases with the increasing length of comb stroke because more snags are produced higher up in the tress, with increasing comb stroke length producing more long segment breaks relative to short segment breaks. However, this LIS effect is not as large as the effect of water versus a moderate relative humidity, as summarized by the data in Table II. We next decided to examine the effect of hair curvature on long and short segment breaks. The results of this experiment are summarized in Table IV in terms of the number of broken hairs and also the LIS ratio. For this experiment, the starting hair was permed in straight and curled configurations, as described in the Experimental section, and then after shampooing and drying was combed in the same manner as in the other experiments, with the exception that the large teeth of the comb were used rather than the fine teeth. The reason for this was that the curled tress provided too high a level of snagging and breakage with the fine-tooth section of the comb. As one would expect, both short and long segment breakage increase with increasing curvature, and the ratio of long-to-short segment breaks also increases. The former effect is a result of more snagging higher up in the tress with increasing fiber curvature, and the effect on the ratio is a result of a larger increase in the long segment breaks relative to short segment breaks. The data for the number of short and long segment breaks produced by brushing versus combing are summarized in Table I, and the ratios for this comparison are summarized in Table V. Brushing clearly provides more long and fewer short segment breaks, producing a Table II Wet-versus-Dry Combing and Hair Breakage Long-to-short segment ratios 60 ± 5% RH LIS* 0.18 * Each number is an average of three replicas. The difference is highly significant, p = 0.0003. Wet 0.99

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