J. Cosmet. Sci.! 58, 477-484 CTuly/August 2007) Hair breakage during combing. Ill. The effects of bleaching and conditioning on short and long segment breakage by wet and dry combing of tresses CLARENCE ROBBINS and YASH KAMATH, 12425 Lake Ridge Circle, Clermont, FL, 34711 (C.R.), and Textile Research Institute, PO Box 6251 Princeton, NJ 08540 (Y.K.). Synopsis A recent publication (1), provided evidence for two types of hair breakage during combing, short segment breakage (approximately less than 1.27 cm) and longer segment breakage. We have confirmed these results and refined the separation distance between short and long segment breakage at about 2.54 cm. Further- more, chemical bleaching increased both short and long segment breakage while a commercial hair con- ditioner decreased both types of breakage. Whether the hair is chemically bleached or conditioned, for dry combing, short segment breakage increases with increasing comb strokes, that is, short segment breakage increases as combing damages the ends of the hair, however, long segment breakage does not increase with increasing comb strokes. Wet combing provided a decrease in short segment breakage and an increase in long segment breaks, but no increase in breakage with increasing comb strokes. Mechanical combing of tresses shows similar results qualitatively, however the variance was too large and adjustments need to be made to provide for a larger number of broken hairs to bring the mechanical and hand combing results in line. For dry combing, as the comb descends through the hair, hairs above it are made parallel and those beneath are either made parallel or knot by, hairs looping around other haits or hairs looping around comb teeth and other hairs several cm between the comb and the hair tips. As the comb advances through the looped/ knotted hairs long breaks occur or as the comb descends near the tips wrapped ends can result. End wrapping by inertia & possibly static charge produces short segment breaks which are more severe if the hair is cut at 90 degrees versus a tapered cut. For wet combing, clumping of hairs by a capillary action produces fewer short segment breaks, by reducing end wrapping however, crossed hair interactions occur & because of higher friction more severe snags arise higher up in the tress, and lower hair breaking load due to plasticization by water, producing a larger number of long segment breaks. The very best practical way to evaluate hair strength is by counting the actual number of short and long segment breaks and by considering both wet and dry combing. INTRODUCTION In a previous paper (1), it was demonstrated that during hand combing of hair, short fiber fragmentation (less than about 1.27 cm) and longer segment breakage occurs by different pathways. It was proposed that longer segment breaks occur primarily by 477

478 JOURNAL OF COSMETIC SCIENCE impact loading of one hair fiber over another which causes breakage at loads lower than tensile break loads, and breakage occurs at the hair-to-hair contact point with essentially no increase in hair length (strain) versus normal tensile loading which produces large strain increases (1,2). But, short segment breakage involves the wrapping of distal ends of hairs around comb teeth as shown by (1,2), thus increasing the end-peak force and with continued combing the ends are damaged more and more ultimately producing an increasing number of short segment breaks. The purpose of this current investigation was to re-examine the cut-off between short and long segment breakage, to investigate the effects of bleaching and conditioning on short and long segment breakage by both hand combing and by mechanical combing of hair tresses, to compare wet and dry combing effects and to develop a better under- standing of how hair snags form during combing. EXPERIMENT AL TRESS MAKING AND PREP ARA TI ON Tresses were made using six grams of 12 inch dark brown Italian hair from DeMeo Brothers, New York, NY for hand combing over the bottom 6 inches (� 15 cm) of the tresses. To produce approximately the same comb stroke distance over the same portion of hair in mechanical combing, 5 grams of 9.75 inch (25 cm), (2.25 inches (5.7 cm) was cut off from the root end of this same 12 inch (30.5 cm) hair tress) dark brown Italian hair was used for making tresses. The tresses were washed with a commercial cleaning shampoo based on sodium laureth sulfate and then dried and carefully detangled both wet and dry using a wide toothed comb. For both mechanical combing and hand combing, some of these tresses were bleached for 45 minutes with product from a commercial bleaching kit containing a peroxide persulfate mixture and then the bleaching agent was carefully rinsed out and the tresses hung up to dry. These bleached tresses were carefully detangled and washed again with the commercial cleaning shampoo and some of these tresses were air dried after detangling and others treated with a commercial hair conditioner, rinsed with tap water, detangled and hung up to dry overnight. HAND COMBING Dry hand combing was at 60 ± 2% RH and room temperature. Prior to combing for collecting hair fragments, the tresses were carefully detangled (10 comb strokes) with a wide tooth comb. The tresses were then combed 25 comb strokes at a rapid comb stroke rate using the fine tooth part of an ACE all purpose comb (#61286) starting each comb stroke at approximately six inches (15 cm) from the tip end of the tress and the broken hair fragments were collected on a large 18 x 24 inch (46 x 61 cm) piece of white poster board and separated by size into groups of less than 1 inch (2.54 cm) length, 1 inch to 2.5 inches (2.5 to 6.4 cm), 2.5 to 5 inches (6.4 to 12.7 cm) and longer than 5 inch lengths (12.7 cm) and the hair fragments in each group counted. Separate combs were used to avoid transfer of conditioner or surface ingredients between tresses. The tresses were combed a 2nd , 3rd and 4th time at 25 comb strokes each for a total of 100 comb