JOURNAL OF COSMETIC SCIENCE 266 length, 5–10 μm) or the chemical heterogeneity of the hair surface. The average sliding angle for virgin hair corresponded to a total average frictional force of 8.8 μN, or 2.2 μN per contact and a static coeffi cient of friction of 0.5. The 4X bleached hair data were not signifi cantly different from the virgin hair according to a t-test. This result refl ected the mild surface damage of the hair, which was assessed by wicking test (section 2.4). In contrast, the relaxed hair, which was hydrophilic (and therefore has signifi cant surface damage), displayed an average sliding angle of 31°—signifi cantly higher than the virgin hair 26°. These data suggested that the incline loop technique might detect hair surface damage. The same hair fi ber set (loops and pairs) was measured at two tensions (10 g and 50 g) and the data are displayed in Table I. The fi ber tension decreased the friction slightly. This could indicate that, at higher tension, the reduced friction related to a decrease of contact area as a result of to cuticle lifting. Treated hair. A typical histogram of angle values for silicone-treated hair is shown in Figure 5, in comparison with the untreated hair data. The treated hair clearly displayed a much broader distribution and a higher average sliding angle compared to the untreated hair. The average low load static coeffi cient of friction for untreated and treated hair is 0.6 and 1.1, respectively. The broad distribution is refl ected by a high standard deviation value. These data suggest that the hair surface treated with silicones presented patches of different adhesion strength. Observations by Bushan with AFM probes also suggested that the hair surface treated with conditioners was patchy and displayed a distribution of adhesion force (1). Histograms of angle values for different silicone treatments at constant dosage 3000 ppm on the hair are shown in Figure 6. A summary table of the analysis data is shown in Table I. All data for silicone-treated hair displayed a broad distribution of angles, which differed clearly from untreated hair. The distribution was closer to a normal distribution for amino ABn, indicating a more even coverage. For the experiments in which the silicone was delivered by a volatile organic solvent, the normal distribution model did not fi t the experimental data well. It is possible that the drying of volatile Figure 4. Sliding angle histograms of untreated hair (N = 50). X-axis: angle in degrees. Upper left: virgin Caucasin hair. Upper right: four time bleached hair. Lower left: relaxed hair. Black line is the normal distribu- tion fi t. [Note: Test data. Actual results may very.]

Table I Analysis Summary Table Tension (g) Dose (ppm) Average angle (degree) Standard deviation sin θ Adhesive tangential force (μN) cos θ Adhesive normal force (μN) Low-load static coeffi cient of friction Angle 90 (%) Virgin 26 6.4 0.44 2.2 0.89 0.5 0 4X bleached 29 7.1 0.48 2.4 0.87 0.6 0 Relaxed 31 7.0 0.51 2.6 0.85 0.6 0 Virgin 10 29 6.7 0.47 2.4 0.87 0.5 0 Virgin 50 25 5.8 0.42 2.1 0.90 0.5 0 Silicone quat 1000 47 15.0 0.71 3.5 0.66 1.1 0 3000 53 27.2 0.71 3.5 0.55 1.3 12 Amino Abn 1000 49 19.2 0.71 3.6 0.62 1.2 4 3000 71 28.5 0.83 4.2 0.32 2.6 22 Aminosilicone 1000 46 20.4 0.66 3.3 0.67 1.0 4 3000 70 35.7 0.77 3.9 0.32 2.4 28 Silicone gum 3000 117 42.6 0.68 3.4 −0.32 1.6 68 2008 TRI/PRINCETON CONFERENCE 267