156 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The actual volume increase from 60 to 100 percent was obtained by subtracting 16 [% vol increase 0 to 60% RH (9)] from the values of the percent weight gain column of Table XII. These values were then multiplied by 0.44 to convert to percent diameter increase (9) and added to the dry diameters determined by linear density for the corre- sponding hair samples of Table X. The data of Table XII show more swelling for the steam set hair (KI) than for the other samples, and, as expected, greater swelling for bleached hair compared to unbleached hair. One sample of SAC-treated hair was evaluated and no effect on water swelling was detected vs the corresponding SLS control. Therefore all SAC-treated hair samples were assumed to have the same wet diameter as the corresponding SLS-treated hair samples. Friction. Frictional resistance was determined for single hair fibers cut from the swatches, as described in the experimental section. Only root to tip friction was mea- sured. The data of Table XIII summarizes the dry (60% RH) friction values of the various hair type/treatment samples employed in this study. In general the bleached hair samples provide the highest frictional resistance, the SLS samples are in the middle, and the SAC- and oil-treated hair provides the lowest frictional resistance. Table XIV summarizes the wet friction data. These data are generally higher than the corresponding dry friction data, consistent with the effect of increasing humidity on keratin friction (4,22). The bleached hair samples also generally produce higher friction values than the corresponding unbleached (SLS) samples, and the SAC-treated samples Table XlII Dry Frictional Resistance of Different Hair Types/Treatments Frictional Load Waller Duncan Hair Type/Treatment Grams Groupings KI- Bleached 6.84 Cau- Bleached 6.68 O- Bleached 6.36 KI-SLS 6.04 KII- Bleached 5.88 O- SLS 5.74 KII-SLS 4.98 Cau-SLS 3.44 KII-SAC 3.14 O-SAC 3.09 KII-Oil 2.83 KII- Bleach/Oil 2.78 Cau- SAC 2.71 O-Oil 2.65 Cau-Oil 2.42 KI-SAC 2.39 KI-Oil 2.35 0.50 0.49 0.48 0.46 0.46 0.45 0.41 0.31 0.29 0.28 0.26 O.25 O.25 0.24 0.22 0.21 0.21 Root to tip friction at 1.1 glTl load. One way ANOVA indicates significance beyond tx = 0.0001 level. Waller Duncan groupings indicate which friction values are different at tx = 0.05 level. Minimum signifi- cant difference = 1.064.

HAIR ASSEMBLY CHARACTERISTICS 15 7 Table XIV Frictional Resistance in Water of Different Hair Types/Treatments Frictional Load Waller Duncan• Hair Type/Treatment Grams Groupings KI- Bleached 14.85 * 0.71 KI- SLS 11.51 •g 0.64 O-Bleached 11.34 0.64 O-SLS 10.31 0.61 Cau- Bleached 8.56 I I 0.5610.530.50.47 Cau- SLS 7.73 KI-SAC-rinse 7.02 O- SAC-ri nse 6.58 I 0.49 Cau-SAC-rinse 6.19 KI-SAC-no rinse 4.60 0.39 Root to tip friction with 1.1 gm load (no correction for buoyancy). •: Waller Duncan groupings indicate which friction values are different at o• = 0.05 level. Minimum significant difference = 2.18. * Significantly different from all other means at o• = 0.05 level. all produce lower friction than the corresponding SLS hair samples. The no rinse value, the lowest wet friction result, was determined in SAC solution as compared to treating fibers with SAC rinsing and soaking, and measuring friction in deionized water. This procedure not only produced lower friction values, but the friction curve was altered, providing no slip stick action in contrast with all other friction determinations, sug- gesting extensive alteration of the hair fiber and/or the mandrel surfaces by this type of treatment. SUMMARY This study shows that it is possible to describe fiber assembly properties such as combing behavior in terms of a few relevant single-fiber properties, i.e., curvature, friction, stiffness, and diameter. Of these four single-fiber properties, fiber curvature has the most important impact on combing behavior and the curvature effect increases as the hair becomes more curly. Fiber friction and stiffness also contribute significantly to combing behavior. However, compared to the other variables, fiber diameter is of less importance to combing behavior. Increasing fiber curvature or friction makes combing more difficult as expected however, increasing fiber stiffness results in lower combing forces. ACKNOWLEDGMENT The authors would like to acknowledge Mr. Richard Polanski for helpful discussions and advice with the statistical analyses. REFERENCES (1) C. R. Robbins and G. V. Scott, Prediction of hair assembly characteristics from single fiber proper- ties,.]. Soc. Cosmet. Chem., 29, 783-792 (1978).