94 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS out at room temperature using a ratio of 2000 ml liquor to i g hair. The hair mounted onto frames was subjected to 5, 10, 15, and 30 cycles of chlorination. Each cycle consisted of soaking the hair for one hour in the chlorine solution, rinsing in water, and drying it for 15 minutes in an air-circulating oven at 40-50øC. The samples for weight loss and tensile tests were subjected to 10, 20, and 30 cycles of treatment. Each cycle consisted of soaking the samples for one hour in the chlorine solution. The samples were then transferred to fresh chlorine solution for the next cycle. After each 10 cycles of such treatment, the samples were rinsed in deionized water. COSMETIC TREATMENTS The hair was treated with either a bleach, dye, or perm treatment at one of two stages in the experiment, either as a pretreatment (before the chlorination procedure) or as a posttreatment (after the chlorination procedure). Control samples were subjected only to the chlorination procedure. Bleach treatment. A 3% H202 solution adjusted to pH 9 was prepared by diluting 30% H202 reagent with 0.1 M ammonium hydroxide. The hair was soaked in the bleach solution for one hour at room temperature using a 2000-ml-liquor to 1-g-hair ratio. After soaking, the hair was rinsed in deionized water and air dried. Dye treatment. A commercial oxidative dye (light auburn) was prepared following package directions. The hair samples were placed on polyethylene wrap and completely coated with the dye emulsion (150-ml to 1-g-hair ratio). The hair was treated with the dye for 30 minutes at room temperature, then rinsed with tap water until the water was clear. Immediately thereafter, the hair was soaked in a 5% sodium lauryl sulfate solu- tion for 10 minutes, rinsed with deionized water, and air dried. Perm treatment. A commercial permanent waving treatment (thioglycolate waving lotion and hydrogen peroxide neutralizer) was applied to hair samples lying on polyethylene wrap (150-ml to 1-g-hair ratio). The hair was soaked in the waving lotion for 30 minutes and rinsed with deionized water. The neutralizer was then applied to the hair and left on for 15 minutes. The hair was again rinsed with deionized water and air dried. ANALYSIS OF FIBER PROPERTIES Fiber properties were determined by methods described earlier (1). The twist method of Lindberg and Gralen (2) for measuring friction was used. Parameters examined included coefficient of friction and "percent stick," the percentage of total time involved in the sticking (positive slope) portion of a stick-slip profile. Surface morphology was studied by the examination of fibers in the scanning electron microscope. Changes in the weight of samples were evaluated by determining dry weights before and after treatment. The force and the work required to extend wet fibers 20% of their original length were measured on a constant-rate-of-extension tensile tester using a crosshead speed of 5 mm/min. Fiber tenacity and knot-breaking tenacity were measured on a constant-rate- of-extension tensile tester, using a crosshead speed of 10 mm/min. The ratio of knot- breaking tenacity to fiber tenacity (K/T) was then determined for each hair fiber.

THE CHLORINE-HAIR INTERACTION 95 Table I Effect of Cosmetic Treatment/Sequence and Cycles of Chlorination on the Coefficient of Friction and Percent Stick of Brown Hair Pretreated Posttreated Cycles Treatment p• s* % Stick s p• s % Stick s 0 Control 0. 130 0.017 36.6 1. 140 Bleach control 0. 196 0.027 38.0 1.225 Dye control 0. 166 0.015 36.8 1.095 Perm control 0. 196 0.015 38.4 0.894 5 Control 0. 180 0.016 38.0 0.707 Bleach 0.230 0.031 42.0 1.871 Dye 0.214 0.023 42.6 0.548 Perm 0.218 0.013 42.2 1.643 10 Control 0.246 0.027 41.8 2. 168 Bleach 0.218 0.028 41.6 2.881 Dye 0.276 0.013 39.2 1.304 Perm 0.234 0.018 42.4 1. 140 15 Control 0.244 0.021 43.2 1.483 Bleach 0.290 0.023 41.4 2. 191 Dye 0.272 0.023 37.8 0.837 Perm 0.254 0.018 43.0 2.828 30 Control 0.278 0.026 46.8 1.304 Bleach 0.326 0.015 52.2 3.421 Dye 0.294 0.036 39.6 0.894 Perm 0.280 0.025 54.6 3.782 0.300 0.035 45.4 2.408 0.193 0.019 38.0 0.816 0.244 0.009 42.6 1.342 0.306 0.025 47.8 2.490 0. 174 0.009 43.2 1.304 0.276 0.011 47.8 4.324 0.326 0.056 49.6 4.393 0.226 0.027 42.4 1.817 0.292 0.019 51.4 4.506 0.262 0.025 44.6 2.608 0.200 0.012 40.0 1.225 0.268 0.017 45.3 2.500 * s = standard deviation for five observations. STATISTICAL ANALYSIS Statistical analysis computations were performed using various procedures of the statis- tical analysis system (SAS). The general linear model procedure and the analysis of variance procedure were used to analyze the sources of variation. Pairwise comparisons were used to determine differences between levels of a given source of variation. All tests of significance were made at the 95 percent level. RESULTS AND DISCUSSION The effect of cosmetic treatment sequence and number of one-hour cycles of chlorina- tion on average values of the coefficient of friction are given in Tables I and II. Treat- ment and cycle effects are evident, with the blond and brown hair showing similar trends. The cosmetic treatments alone significantly increased the coefficients of friction beyond that of the untreated controls (0 cycles). When the cosmetic treatments pre- ceded chlorination, coefficients of friction generally increased with increased cycles of chlorination. This continual increase was similar to that of the control samples. These results indicated a gradual softening of the surface of the fibers, first with the cosmetic treatments and then with continual chlorination.