630 JO URN AL OF COSMETIC SCIENCE York City. The hair photographs were made using a Nikon D2X camera equipped with a 55-mm close-up lens. COMBS AND BRUSHES USED A Goody "flat" brush with holes in the back was used (see Figure 1). It was 22.2 cm long with a handle 10.2 cm long. The bristles were a white plastic with blue bulbous tips. The bristle shaft diameter was 0.1829 cm, the bristle shaft length 1.9 cm, and the bristle bulb diameter 0.2134 cm. A cylindrical Priven styling brush with a wooden 11-cm long handle was attached to a 2.2-cm diameter shaft containing plastic bristles (see Figure 1). The bristles were 1 cm long with a bristle shaft diameter of 0.0762 cm and bristle bulbs 0.1118 cm in diameter. An Ace comb #61286, the same type of comb used in the previous hair breakage experiments was used in these studies. PREPARATION OF HAIR FOR CURVATURE EXPERIMENTS One-gram tresses of the DeMeo hair described above was permanent-waved in straight and curled configurations using a commercial ammonium thioglycolate home wave for normal-to-wave hair in the following manner. For the curled hair, each tress was wet with 2 grams of waving lotion, wound tightly around a 6-mm rod, and bound at the top and bottom with rubber bands. It was wet with waving lotion a second time after ten minutes, and then after 20 minutes it was rinsed with 20 ml of water and allowed to stand on the rod for another ten minutes. Neutralizer was then added. After remaining Figure 1. Two different brushes used in this work. Ar the top is the Goody "flat" brush and at the bottom is the styling brush.

HAIR BREAKAGE DURING COMBING AND BRUSHING 631 on the rods for another five minutes, the tress was removed from the rods and more neutralizer was added while massaging it through the hair. The tress was rinsed thor­ oughly with water and blotted dry with a towel before air drying. For straightening hair, the same process was applied as above, but the tress was squeezed between the forefinger and the thumb from top to bottom in order to form it into a straight configuration. This same process was applied for each addition of waving lotion, rinse, and neutralizer. Four weeks later (for convenience only) the tresses were shampooed, rinsed, and dried and used in the combing experiment testing for the curvature effect. The combing was for 25 strokes 15.2 cm long, using the wide-tooth spacings of the Ace comb described above. BRUSHING HAIR After experimenting with brushing variables, the following procedure was adopted for consistency. Three-gram tresses of the hair described above, both non-bleached "virgin" hair and bleached hair (using the bleaching procedure described in our former paper (4)) were brushed (15 .2-cm brush stroke) after shaking the tress three times and then brushing it 50 strokes, pausing to collect hairs at ten-stroke intervals. The tress was held lightly at the bottom of the brush with the thumb and engaged into the brush bristles at about a 45° angle. The brush was then pulled through the hair rapidly while the thumb continued to hold the hair at the bottom of the brush. COMBING HAIR Combing of hair and statistical analysis was as described in our previous paper (4), with the exception that in the case of the curvature experiment the comb teeth with wide spacings were used. Combing was for only 25 strokes, and only hair segments 2.54 cm or longer and those shorter than 2.54 cm were collected. For the length-of-comb-stroke experiment, the fine-tooth part of the comb was used with 50 comb strokes, and hair fragments were collected at 2.54 cm or longer and shorter than 2.54 cm. RESULTS AND DISCUSSION As indicated above, hair fibers break during combing by two primary pathways, pro­ viding for long (3) and short (4) segment breaks. Long segment breaks occur primarily by a hair fiber looping over another hair and impacting on it, and short segment breaks occur primarily by end wrapping via abrasion and deformation. Since we had already shown that bleaching increases both short and long segment breakage, and conditioning decreases both short and long segment breakage (4), for this paper we decided to examine other important variables involved in combing and also to look at brushing. In addition, we decided to look at the effect of the ratio of long-to-short segment breaks as a means to show how these two different pathways of breakage are affected by these variables.