32 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS o o • o o direction of scan in mm Figure 5. Chosen hair fiber (virgin brown hair, scan length 0.4 mm, pyramidal stylus). Reproducibility. Repeated scanning of defined segments of the hair surface showed almost constant values for roughness parameters (Table III). The direction of scanning was root to tip. Scanning in the opposite direction does change the surface, presumably because the stylus is lifting cuticular cells from supporting cell layers (Figure 7, left half of picture). Distribution of roughness values of hair fibers from difjSrent hair strands. Figure 8a shows the average distribution of the amplitudes of 14 scans (scan length: 10 mm) performed on Table I Mean Values of Roughness Parameters of 20 Hair Fibers Scanned at Different Distances From the Root (scanning lengths 0.4 and 1.25 mm) Scanning Distance length (mm) (mm) Rq Rt Rz hq Pc 7 0.4 • 0.201 0.83 0.44 4.4 1168 s 0.033 O. 152 0.095 0.457 69.9 1.25 • 0.373 1.51 1.08 4.7 1063 s 0.114 0.461 0.234 1.087 106.6 62 0.4 i 0.216 0.86 0.45 5.1 1144 s 0.037 0.125 0.064 0.579 97.5 1.25 • 0.411 1.60 1.08 5.0 1042 s O. 128 0.383 O. 177 0.876 133.4 mean-value. standard deviation.

PROFILOMETRY OF HAIR 33 1.25 1.00 0.75 0.50 0.25 o. GO ..__/ /% age (weeks) Figure 6. Surface roughness of a single hair fiber at segments of different age (weeks) (assuming a speed of growth of 0.3 mm/day). Table II Roughness Parameters and Peak Counts of a Single Hair Fiber as Function of Changing Scan Length -- Scan-length-- 40 nm 12.5 nm 4.0 nm 4.0 nm 1.25 nm 0.4 nm Rq 3.5 1.5 0.8 0.71 0.36 0.18 R t 14.0 4.6 3.4 2.7 1.4 0.7 Rz 7.6 3.4 2.0 2.0 1.1 0.4 q 0.8 0.8 3.3 1.9 4.1 3.9 Pc - - - 520 1043 1225 Table III Repeated Measurement of an Identical Segment of One Arbitrarily Selected Hair Fiber (scan length 12.5 mm) Parameter Rt x Rt2 Rt3 Rt4 Rt5 Ra Rq Rp Aq 1. scan 5.6 7.1 3.5 4.8 5.6 1.10 1.39 3.2 1.0 2. scan 5.6 6.9 3.5 4.8 5.5 1.11 1.39 3.2 1.0 3. scan 5.6 6.8 3.5 4.8 5.6 1.11 1.39 3.2 1.0 Rt•... 5 are defined as maximum/minimum distances of five segments of the whole scan length.