ALIGNMENT CONTROL AND SOFTNESS CREATION IN HAIR 21 In this study, we have investigated the effect of fi ber alignment on the perception of hu- man hair softness, together with a study of the role of a new softening agent, glycylgly- cine (GG), and attempted to connect consumer perception with tangible measurements of fi ber properties. Stress relaxation, assessment of hair initial elastic modulus, and atomic force microscope (AFM) force measurements have been performed to evaluate the changes in hair fi bers after treatment with GG. EXPERIMENTAL HAIR SAMPLES In this study, hair samples for the physical measurements were obtained from a tress of heavily damaged (by bleaching) curly hair provided by a Japanese female volunteer, aged 32 years. For perception tests, hair samples were obtained from a virgin straight tress, collected from a Japanese female volunteer, aged 35 years, and a virgin naturally curly tress, collected from a Japanese female volunteer, aged 32 years. All hair samples were initially around 30 cm in length. For AFM force measurements on hair cross sections, 15-mm length samples from both the roots of the naturally curly Japanese hair fi bers and the tips of the damaged curly Japanese hair fi bers were then selected. For the model damage experiment to show the effect that damage has on the alignment and shape of an otherwise healthy hair bundle, a virgin straight hair tress (approximately 8 g) was subjected to a chemical treatment comprising of permanent waving, followed by 15 cycles of shampooing, conditioning, and blow drying. The tress was then bleached and followed by another 15 cycles of shampooing, conditioning, and blow drying. The bleaching and washing process was repeated fi ve times, in total. The permanent waving treatment was carried out using a commercially available permanent wave/straightening product containing approximately 4.7% thioglycolic acid (liquid 1) and approximately 8.7% sodium bromate (liquid 2). Liquid 1 was applied for 10 min at room temperature, in a ratio of 1:2 (hair/bath). After rinsing for 30 s under warm running tap water, liquid 2 was applied to the tress for 10 min at room temperature, also in the ratio 1:2 (hair/ bath). The tress was then shampooed, using a plain shampoo formulation, for 30 s, before rinsing for 30 s under warm running tap water. The tress was then blow dried. The bleaching treatment was also carried out using a commercially available product, con- taining approximately 1.3% ammonia, 1.0% monoethanolamine, and 3.4% hydrogen peroxide. The processing conditions were 30 min and 30°C, at a hair/bath ratio of 1:1. After processing, the tress was rinsed under warm running tap water for 30 s, shampooed for 15 s, rinsed and shampooed again, and then rinsed for 15 s and blow dried. The wash- ing cycle applied between each treatment consisted of shampooing, with the plain formu- lation, for 30 s, followed by the application of a simple conditioner for 30 s, and then rinsing under warm running tap water for 30 s. Finally, the tress was blow dried. TREATMENT CONDITIONS The treatments used throughout this study are given in Table I. The level of GG used for these experiments was 2%. Prepared solutions were equilibrated at 40°C in a water bath

JOURNAL OF COSMETIC SCIENCE 22 for several hours before use. All samples were individually tagged with small pieces of electrical insulation tape and numbered with waterproof marker pen before being treated by placing the samples of each set (untreated control, control treatment, GG treatment N = 10 per set) in a shallow glass dish and covering with 20 ml of the relevant solution. After treatment for 30 min at 40°C, the samples were rinsed with deionized water for 30 s and air dried at 20°C/20% RH for at least 36 h. Before the perception evaluation, the tress was treated by immersion in an excess of the GG treatment for 30 min at 40°C, rinsed with deionized water for 30 s, and then air dried at 20°C/20% RH for at least 36 h. SOFTNESS PERCEPTION EVALUATIONS Fifteen experienced researchers were chosen as panelists for evaluating the softness of six tresses containing samples of the virgin straight and naturally curly Japanese hair. Mean curl radii of both types of hair were estimated by measurements on 100 randomly drawn fi bers from each initial tress. Curl radius was measured by placing the hair on a template of accurately drawn concentric circles of known radii. The straight hair showed a mean curl radius of 56.6 ± 22.0 mm, whereas for the curly hair the mean radius was 21.7 ± 17.9 mm, a statisti- cally meaningful difference at the 99% confi dence level (as determined by the Student’s t-test). For the perception test, the curly hair content of each tress was 0%, 2%, 5%, 10%, and 20%, by weight. A second tress containing 20% curly hair, by weight, was prepared and treated with an excess of the GG treatment as described earlier. Each tress weighed 5 g. The panelists were blindfolded and were asked to handle each tress and arrange in order in terms of softness. The order provided by each panelist was recorded and converted into a six-point scale, according to the frequency with which each tress was positioned. Each panelist was individually interviewed and asked to describe how they felt softness when touching their hair. Their comments were recorded, and then frequently occurring key points were extracted. EVALUATION OF THE STRESS REQUIRED TO STRAIGHTEN UNRULY HAIR The maximum load required to straighten an unruly tress during typical fi nger combing and teasing motions, such as would be performed by consumers when assessing the state Table I Treatment Compositions Ingredient Composition/wt (%) Control formulation GG formulation Lactic acid 4 4 Benzyl alcohol 1 1 GG 0 2 Deionized water Balance Balance pH To 3.7 To 3.7