144 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and the curled length, L o of 15 of the longest hairs measured with the fibers hanging freely. Generally L c of the single hairs was in agreement with the average length of fibers hanging in the tress except for some oil-treated hair and for wet hair. The number of wave crests (N) in the hair were then counted to the nearest « N with the fiber hanging freely by its root end. A one-gram alligator clip was attached to the tip end of the hair and the taut length measured (LT). The curvature was then calculated from this expression: C = N/(Lc/L T) (1) The value of L c from single hairs was used except when it varied from the average length of fibers in the tress, in which case the latter measurement was used for L o Each value is an average from at least 15 different hairs. FRICTION MEASUREMENT Frictional resistance was measured by a capstan procedure with an Instron © attachment similar to that described by Scott and Robbins (4). The load hanging from the fiber was 1.1 grams, the angle of wrap 210 degrees, crosshead speed 0.051 cm per minute, and chart speed 2.54 cm per minute. Dry measurements were made at 60 --- 5% RH. Wet measurements were at 65 to 70 degrees F after soaking the hairs for 1 hour in deionized water. Mandrels were washed with absolute ethanol and dried after every third run. Friction values were measured at two different spots on each fiber, approximately 2.5 cm apart, and generally 10 fibers were measured for each friction value. The no-rinse sample was evaluated by determining friction with the entire setup immersed in 1% SAC in 30:70 ethanol:water. DIAMETER MEASUREMENTS Li,ear de,sity. Dry fibers were measured for length to the nearest millimeter and weight to the nearest 0.01 mg using a Roller Smith 3-mg Precision Balance (5). Assuming circularity, and a density of 1.32, diameters were calculated (6). Microscopy. As a cross check on the linear density method and to test the effects of bleaching on fiber diameter, 10 fibers from each hair type were glued to microscope slides and measured for diameter using a filar micrometer calibrated with stainless steel suture wire of known diameter (7). Five spots on each hair were measured and averaged. The calibrated fibers from O and KI hair were bleached as described above and diam- eters remeasured. Centrifugation. To estimate wet fiber diameters the centrifugation (8) method was em- ployed in the following manner. Hair samples from the tresses were cut into approxi- mately one-inch lengths and placed into 70-mm capped vials and tap water (100 de- grees F) added until the hair was completely immersed (approximately 13 ml water). After 10 minutes soaking, the water was decanted, the hair removed with forceps and blotted with filter paper, and placed in 11 X 100-ram test tubes with tissue paper in the bottom and centrifuged for 20 minutes. The hair was then removed into pre- weighed weighing bottles, weighed, and then dried in a vacuum desiccator overnight

HAIR ASSEMBLY CHARACTERISTICS 145 and reweighed. The percent diameter change was computed from the percent weight changes by the relationship Y = 0.44 X, calculated from data by Stam and cowork- ers (9). STIFFNESS A fiber of 5-cm gauge length was extended at a rate of 0.05 cm/min with chart speed at 12.7 cm/min using an Instron © Model TM with Tension Cell A set at 10 grams full scale load. From the linear portion of the charted tracing, the elastic slope was esti- mated as grams per mm extension (H) of the 5-cm fiber. Each stiffness value was generally an average from 15 fibers. For dry stiffness the RH was 60 ___ 5%. Wet stiffness measurements were made in deionized water after soaking the fibers for one hour. RESULTS AND DISCUSSION RELATIONSHIPS BETWEEN HAIR COMBING BEHAVIOR AND SINGLE FIBER PROPERTIES In the previous paper (1) it was hypothesized that changes in combing behavior could be described by six primary single-fiber properties measured under conditions relevant to combing behavior: K(Combing Ease) = f(Fs,Fk,S,C,D,E) (2) Equation (2) suggests that static friction (Fs), kinetic friction (Fk) , stiffness (S), curva- ture (C), diameter (D), and static charge (E) are all relevant to combing behavior. Furthermore, if one considers any particular consumer's hair described by K (combing ease), then the change produced by treatment of this hair is represented by equation 3. combing ease = -(N 1 ß Fk) -- (a 2 ß F s) - (a 3 ' E) + (nl' S) + (n2 ß D) - (N4' C) (3) Thus this hypothetical expression describes the effects of a treatment on combing be- havior of hair and suggests that combing behavior is influenced primarily by changes in fiber friction, static charge, and fiber curvature, with smaller contributions (small n) from fiber stiffness and diameter. In this study several experiments were conducted to test the effects of single-fiber prop- erties on combing behavior. Combability measurements were made by the method of Garcia and Diaz (3). Peak combing load (PCL), the highest load (in grams) during the combing of a swatch, and work of combing (ACL) in gm-cm were the quantitative criteria for combing behavior. Specifically the average PCL and ACL from three consec- utive combing runs of 5 to 10 tresses was employed. The actual combing data were developed in seven separate experiments and are summa- rized in Tables I and II. Each experiment of Table I was analyzed by both parametric and nonparametric statistical tests. The statistical conclusions are generally similar, but in the few instances where the analyses provide differences the nonparametric tests were the more sensitive. This is probably because of unequal variances or distributions that are not normal, necessary assumptions for ANOVA but not for the nonparametric tests. The ACL values of Table II were analyzed only by a nonparametric statistical test.