PROFILOMETRY OF HAIR 35 o o o o o o o direction of scan in mm Figure 9. Surface profile of a hair fiber (scan length 4 mm, axe-shaped stylus). sponding to a wavelength of 0.4 mm. If hair growth is regulated by circadian rhythms as the basal layer of the epidermis and other skin appendages are, then daily periodic changes of the fiber's diameter are possible. o o C O. O0 ß ß ß ß i i 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 frequency (1/mm) Figure 10. Averaged amplitudinal spectrum of five hair fibers (brown, scan length 10 mm).

36 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 frequency 4.0 ( 1/ram) Figure 11. Averaged amplitudinal spectrum of 13 virgin hair fibers (scan length 40 mm). Fourier analysis of longer scan lengths yield a main distinct maximum at 0.1- 0.2 (per millimeter), corresponding to a wavelength of about 10 mm, which would be a growth rate of 28 days, a menstrual cycle (Figure 11). This would agree with Figure 8a and be in accordance with profiles consisting of sharp mountains and broad valleys. Cosmetic treatment. Table IV shows small differences between brown, blonde, and bleached hair fibers. The tested blonde hair fibers showed the least roughness, while the bleached fibers showed the most. Changes of roughness due to the drying of wet hair can be seen in Figures 12a and 12b. The hair samples had been placed in water of 30øC for three minutes. Then a series of Table IV Roughness Parameters of Hair Fibers From Different Strands (scan length 10 mm) Brown hair Blonde hair (N = 5) (N = 4) Bleached hair (N = 4) Rz = 9.970 •m 9.302 (ya z = 2.959 •m 2.083 Rp = 7.759 •m 7.635 (Yap = 2.517 •m 2.183 R s = 2.572 •m 2.264 (Ya• = 1.018 •m 0.603 Rq = 3.250 •xm 2.788 = 1 365 •m 0.750 (YRq ß [R•/Rq] = 0.791 0.812 .tm 11.547 •m .tm 2.940 •m .tm 8.536 •m .tm 3. 544 •m xm 3.026 •m xm 1. 153 •m xm 3.680 •m .tm 1.435 0.822