2006 TRI/PRINCETON CONFERENCE 479 strokes per tress and the fragments collected by size and counted. The data was analyzed statistically by a modeling program from Statistical Analysis Systems (3). A similar procedure was followed for wet combing with the following changes. Each tress was washed with the commercial cleaning shampoo on the previous day and detangled with a comb when wet. The following day one tress was wet with water under the tap and placed in 125 ml of tap water (American Water Co.) in a 250 ml beaker for 2 minutes and then the water squeezed out between the forefinger and thumb into the beaker and the tress combed 10 comb strokes starting the combing at the mid-point of the tress. Broken hairs were removed from the tress onto an 18 x 24 inch piece of white fiber board and then the tress was combed another 15 comb strokes and all hair fragments carefully removed from the comb and then the tress was dipped into the beaker with water and swirled and water and hair removed by squeezing with the fingers 3 times to remove small broken hair clinging to the hair tress. The beaker was allowed to stand for at least 3 minutes, then the small hairs generally less than 0.64 cm (1/4 inch) were counted in the beaker. Hairs were separated by size 0.64, 1.27, 2.54, 6.35, 12.7 cm and counted. Each tress was combed a 2nd 3rd and 4th time, as above separating and counting the hairs by size in the same manner. The data from all combing experiments was analyzed statistically by a modeling program from Statistical Analysis Systems (3 ). MECHANICAL COMBING The tresses were detangled carefully using a wide tooth comb (separate combs used to avoid transfer of conditioner or surface ingredients between tresses) and stored prior to mechanical combing. The tresses were combed (at 60 to 65% RH and room temperature) at a comb stroke rate of 80/min for 1000 or 2000 comb strokes using the fine toothed portion of an ACE all purpose comb [(#61286) (same as for hand combing using separate combs per tress)} and the broken hair fragments were collected and saved for counting. The data was analyzed statistically by a modeling program from Statistical Analysis Systems (3). RES UL TS AND DISCUSSION HAND COMBING The data of Table I confirms the conclusions from the earlier study showing more short segment hair fragments ( 2.54 cm) than long segment fragments (2.54 cm) and an increase in short segment breakage with increasing comb strokes (1). These data versus the previous data also show a better cut-off between long and short segment breakage at 2.54 cm (1). An increase in short segment breakage occurs with increasing combing damage near the ends of the hair fibers resulting in an increase in the number of short segment breaks, but a similar effect does not occur for long segment breakage, that is the number of long segment breaks does not increase with an increasing number of comb strokes. This effect confirms the previous finding and suggests a different mechanism for long versus short segment breakage as suggested in the previous publication (1). Short

480 JOURNAL OF COSMETIC SCIENCE Table I Long versus Short Segment Breakage and Hair Length* Number of broken hairs at length (cm) (average of 3 replicas) No. of comb strokes 2.54 2.54-6.4 6.4-12.7 12.7 25 28 4 1 50 44.3 4.7 1 1 75 45.7 3.7 1.3 1.3 100 68.7 5.3 0.3 2 * Dry combing at 60 ± 2% RH. Significant difference in breakage by lengths, p = 0.0001. No. of short segment breaks increase with no. of comb strokes (p = 0.001). No. of long segment breaks do not change with no. of comb strokes (p = 0.29). segment breakage most likely occurs primarily by end wrapping and subsequent damage to the ends of the fibers by abrasion and deformation and ultimately breakage occurs primarily by deformation when the ends are sufficiently weakened. The wrapping of distal ends of hairs around comb teeth (1,2), increases the end-peak force and with continued combing the ends are damaged more and more, producing fiber/fiber en- tanglements, and consequently an increase in the number of short segment breaks. The wrapping of hair ends around comb teeth during combing most likely is driven by inertia in which the motion of the comb through the hair near the tip, especially where the hair has a slight curl at the end, produces a tendency for hair fibers to move and curl around the comb teeth (1,2). Since more numerous short segment breaks occurs in the dry than wet state, static charge may also be involved in end wrapping. This end breakage effect is consistent with an effect found by Garcia! et al. (4) who studied cuticle wear patterns among 6 Caucasian subjects who had never chemically treated their hair in which their hair ranged from 30 to 60 cm long. These scientists found that hairs 30 cm long on the scalp had lost many more cuticle cell layers at the distal ends than 60 cm hair at a distance of 30 cm from the scalp. They concluded that "at any common distance from the scalp x, the preservation of the cuticle is better for a longer hair subject", because of greater wear and breakage at the ends. The "distal-end-scale-loss" effect observed by these scientists is most likely due to the end wrapping effect described above. As described earlier (1), long segment breakage most likely involves impact loading of one hair fiber against another and is dependent on the probability that taut crossover hairs occur in snags and one hair impacts over another as the comb breaks through or detangles the snag. The data summarized in Table II shows the effects of hair bleaching on short ( 2.54 cm) and long segment (2.54 cm) breakage when hand combing Caucasian hair dry. The hair was bleached with a peroxide-persulfate commercial bleaching product as described in the Experimental section. These data show a significant increase in both long and short segment breakage by bleaching and significantly more short versus long segment break- age. For the short segment breakage, chemical bleaching increases interfiber friction and makes the ends more susceptible to damage by combing. Therefore, bleaching increases short segment breakage which also increases with the number of comb strokes. For the long segment breakage (Table III), bleaching increases inter-fiber friction thereby in-