62 JOURNAL OF COSMETIC SCIENCE using a goniophotometer. The effect of fiber characteristics, such as fiber diameter, ellipticity, and curvature, on luster is demonstrated. The general model for light scat­ tering is used for showing how scattering by microscopic and macroscopic surface roughness, as well as scattering and absorption processes by the hair's interior, affect the position of the specular reflectance peak and its broadening. Absorption characteristics of the fibers are found to play a major role on the luster of hair. Results indicate that the specular peak broadening is one of the important features to take into account when evaluating luster. Therefore, a new equation for luster calculation from GP curves has been proposed. It takes into account the broadening of the specular reflection peak that reduces luster values. Furthermore, by using normalized W112 values in the equation, a dimensionless luster value is obtained. Luster defined by equation 4 can be adopted as a standard for hair. ACKNOWLEDGMENTS These studies were carried out in conjunction with the TRI project "Analysis and Quantification of Hair Damage," supported by a group of TRI corporate participants. REFERENCES (1) C. Reich and C. R. Robbins, Light scattering and shine measurements of human hair: A sensitive probe of the hair surface,]. Soc. Cosmet. Chem., 44, 221-234 (1993). (2) A. Guiolet, J. C. Garson, and J. L. Levecque, Study of the optical properties of human hair, Int. J. Cosmet. Sci., 9, 111-124 (1987). (3) H. K. Bustard and R. W. Smith, Investigation into the scattering of light by human hair, Applied Optics, 30, 3485-3491 (1991). (4) W. Czepluch, G. Hohm, and K. Tolkiehn, Gloss of hair surfaces: Problems of visual evaluation and possibilities for goniophotometric measurements of treated strands,]. Soc. Cosmet. Chem., 44, 299-317 (1993). (5) R. Schueller and P. Romanowski, Evaluating shine on hair, Cosmet. Toiletr., 116, 12, 47-52 (2001). (6) E. Tolgyesi, D. W. Coble, F. S. Fang, and E. 0. Kairinen, A comparative study of beard and scalp hair, J. Soc. Cosmet. Chem., 34, 361 (1983). (7) C. Nappe and M. Kermici, Electrophoretic analysis of alkylated proteins of human hair from various ethnic groups,]. Soc. Cosmet. Chem., 40, 91 (1989). (8) J. A. Swift, "Morphology and Histochemistry of Human Hair," in Formation and Structure of Human Hair, P. Jolles, H. Zahn, and H. Hoecker, Eds. (Birkhauser Verlag, Basel, 1997), pp. 149-175. (9) R. F. Stamm, M. L. Garcia, and J. Fuchs, The optical properties of human hair. I. Fundamental considerations and goniophotometer curves,]. Soc. Cosmet. Chem., 28, 571-599 (1977). (10) C.R. Robbins, Chemical and Physical Behaviour of Human Hair (Springer-Verlag, New York, 1994), pp. 211-226. (11) C. Hadjur, F. Fiat, M. Huart, D. Tang, and F. Leroy, Morphology of the cuticle of African hair, Second International Symposium-Ethnic Hair & Skin: New Directions in Research, Chicago, 2003. (12) S. Nagase, S. Shibuichi, K. Ando, E. Kari ya, and N. Satoh, Influence of internal structures of hair fiber on hair appearance. I. Light scattering from the porous structure of the medulla of human hair, J. Cosmet. Sci., 53, 89-100 (2002). (13) C.R. Robbins, Chemical and Physical Behaviour of Human Hair (Springer-Verlag, New York, 1994), pp. 327-330. (14) A. Franbourg, P. Hallegot, F. Baltenneck, C. Tontain, and F. Leroy, Current research on ethnic hair, J. Am. Acad Dermatol., 48, 6, S115-S119 (2003).

LIGHT SCATTERING FROM ETHNIC HAIR FIBERS 63 (15) M. Feughelman, "Morphology and Properties of Hair," in Hair and Hair Care (Cosmetic Science and Technology Series, Vol. 17), D. H. Johnson Ed. (Marcel Dekker, New York, 1997), pp. 3-8. (16) R. F. Stamm, M. L. Garcia, and]. J. Fuchs, The optical properties of human hair. II. The luster of hair fibers,]. Soc. Cosmet. Chem., 28, 601-609 (1977). (17) K. Keis, K. R. Ramaprasad, and Y. K. Karnath,]. Cosmet. Sci., submitted. (18) J.B. Hamilton, in The Biology of Hair Growth, W. Montagna and R. A. Ellis, Eds. (Academic Press, New York, 1958). (19) Y. K. Karnath, S. B. Hornby, and H. D. Weigmann, Mechanical and fractographic behavior of negroid hair,]. Soc. Cosmet. Chem., 35, 21-43 (1984). (20) C. R. Robbins and C. Reich, Prediction of hair assembly characteristics from single-fiber properties. II. The relationship of fiber curvature, friction, stiffness, and diameter to combing behavior,]. Soc. Cosmet. Chem., 37, 141-158 (1986).