LIGHT REFLECTION FROM HAIR 315 CONCLUSION The high-resolution, optical probing of the surface and interior of a hair fiber is enabled by fast data acquisition through simultaneous multi-angle goniophotometry, which gives quick access to the light reflection curve of a single hair at any given position along its length. By fitting up to three Gaussian peaks to the GP curve, the different types of reflected light are determined with respect to their receptor angles and intensity distributions. From the data, detailed insight into the reflection of light from hair and its changes along the hair length are gained. Specific changes of the parameters are observed for the three hair types and along the hair length that can be attributed to the antagonistic effects of hair damage and grooming as well as to other phenomena that are currently not well understood. The next, immediate step of these investigations is to derive a measure of luster for human hair from the observations on light reflection (22). REFERENCES (1) (2) (3) (4) (5) (6) (7) (8) (9) (lO) (11) (12) (13) (14) (15) (16) (17) H. K. Bustard and R. W. Smith, Studies of factors affecting light scattering by individual human hair fibres, Int. J. Cosmet. Sci., 12, 121-133 (1990). R. F. Stamm, L. M. Garcia, and J. J. Fuchs, The optical properties of human hair. II. The luster of hair fibers, J. Soc. Cosmet. Chem., 28, 601-609 (1977). M. Hailer, H. Schmidt, and G. Sendelbach, Measurement of the optical paths of light in hair, Poster 42, Proc 21 't IFSCC Int. Congress, Berlin, 2000. 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). Y. Tango and K. Shimmoto, Development of a device to measure human hair lustre,J. Cosmet. Sci., 52, 237-250 (2001). C. Reich and C. Robbins, Light scattering and shine measurements of human hair: A sensitive probe of the hair surface, J. Soc. Cosmet. Chem., 44, 221-234 (1993). W. Haertl, R. Klemp, and H. Vetsmold, Crystallization and characterization of crystallites in charge stabilized suspensions, Phase Transitions, 21, 229-235 (1990). R. F. Schmidt and G. Thews, Eds., Physiologie des Menschen (Springer-Verlag, Berlin, 1995), Chapter 16. W. Czepluch, G. Hohm, and K. Tolkiehn, Gloss of hair surfaces: Problems of visual evaluation and possibilities for goniophotometric measurements of treated strands,J. Soc. Cosmet. Chem., 44, 299-318 (1993). J.A. Swift, Human hair cuticle: Biologically conspired to the owner's advantage, J. Cosmet. Sci., 50, 23-47 (1999). R.F. Stamm, M. L. Garcia, and J.J. Fuchs, The optical properties of human hair. I. Fundamental considerations and goniophotometer curves, J. Soc Cosmet. Chem., 28, 571-599 (1977). E. Schulze zur Wiesche, Untersuchungen zur haarpflegenden Wirkung yon Henna, MSc Thesis, Aachen University of Technology, 1995. S. Nagase, S. Shibuichi, K. Ando, E. Kariya, M. Okamoto, R. Yakawa, A. Mamada, and N. Satoh, Light scattering control at the medulla enhances human hair shine: Internal structures of hair fiber and its shine, Proc 21 st IFSCC Int. Congress, Berlin, 2000, pp. 153-159. J. H. S. Rennie, S. E. Bedford, and J. D. Hague, A model for the shine of hair arrays, Int. J. Cosmet. Sci., 19, 131-140 (1997). Statistica for Windows (computer program manual) (StatSoft Inc., Tulsa, OK, 1999). J. H. Zar, Biostatistical Analysis (Prentice Hall, NJ, 1996). M. L. Tate, Y. K. Kamath, S. B. Ruetsch, and H.-D. Weigmann, Quantification and prevention of hair damage, J. Soc. Cosmet. Chem., 44, 347-371 (1993).

316 JOURNAL OF COSMETIC SCIENCE (18) M. Gamez~Garcia, The cracking of human hair cuticles by cyclic thermal stresses,J. Soc. Cosmet. Chem., 49, 141-153 (1998). (19) M. L. Garcia, J. A. Epps, R. S. Yare, and L. D. Hunter, Normal cuticle-wear patterns in human hair, J. Soc. Cosmet. Chem., 29, 155-175 (1978). (20) G. H. Henderson, Fractography of human hair, J. Soc Cosmet. Chem., 29, 449•467 (1978). (21) A. N. Parbhu, W. G. Bryson, and R. Lal, Disulfide bonds in the outer layer of keratin fibers confer higher mechanical rigidity: Correlative nano-indentation and elasticity measurement with an AFM, Biochemistry, 38, 11755-11761 (1999). (22) F.-J. Wortmann, E. Schulze zur Wiesche, and B. Bourceau, Analyzing the laser-light reflection from human hair fibers. II. Deriving a measure of luster, J. Cosmet. Sci., in preparation.