38 JOURNAL OF COSMETIC SCIENCE 1 5 0 ....-----------------------, 140 ca 120 E ·;;: ca :i E I! en 0 . !!! :::c 100 0 Peak Maxima / Peak Minima 50 100 150 200 Vertical Distance (Horizontal Line Number) Along Fiber Axes 250 Figure 8. Horizontal luminosity analysis horizontally along a hair tress. The abscissa corresponds to each horizontal line in Figure 6, while each ordinate represents the maximum value obtained from either the maxima histogram (Figure 7 A) or the minima histogram (Figure 7B). Table I Results of Maxima/Minima Analysis for Various Types of Hair Medium Light Dark Medium Light Natural Oriental brown brown blonde blonde blonde white Maximum area 13,780 15,860 19,020 20,690 24,580 26,140 46,600 Minimum area 428 4,131 7,369 10,200 12,840 17,380 40,020 Maximum - minimum 13,350 11,730 11,650 10,490 11,740 8,765 6,586 LStamm * 0.72 0.70 0.65 0.32 LReich-Robbins * 0.67 0.32 0.19 0.06 * From reference (1). from the smaller face. It has also been suggested that microreflections from hair arise due to the internal porous structure of hair typically found in medullated fibers (3 ). As a final point, it has been suggested that such light patterns observed on hair may be due to diffraction, with the cuticular structure of hair acting as a diffraction grating (termed blazed grating) (4). We are most inclined to concur with the latter explanation, since the reflection patterns we have observed typically represent a spectrum of colors analogous to that observed with a diffraction grating when white light is split into its various wavelength components.

Cl) :::, 0" SPECULAR REFLECTION IN HAIR 39 200 150 100 50 16 48 81 113 145 177 210 242 274 306 339 371 403 435 468 500 532 565 597 629 Distance (µm) Figure 9. Histogram for the frequency of appearance for distances between peak maxima. A bimodal distribution at 81 µm and 145 µm was observed for all hair types analyzed. Table II Frequencies of Appearance for Distances Between Peak Maxima of 81 µm and 145 µm for Various Types of Hair Medium Light Dark Medium Light Natural Oriental brown brown blonde blonde blonde white 81 µm 410 332 262 154 234 222 260 145 µm 228 202 171 154 159 160 190 Total population 1007 878 717 560 669 616 769 Table III Frequencies of Appearance for Distances Between Peak Maxima of 81 µm and 145 µm for Untreated and Sebum-Treated Dark Brown Hair 81 µm 145 µm Total population Untreated 191 176 671 ANALYSIS OF REFLECTION PATTERNS FROM AFRICAN HAIR Se bum-treated 207 158 645 African hair provides an interesting substrate for optical analysis due to the multiple curls that are naturally present. As shown in Figure 10, the curls provide multiple