280 JOURNAL OF COSMETIC SCIENCE z.bo •.oo e.bo DC Hin _n,,, • ,'----- Spect•u. b DC Min Figure 6. AFM: surface distance analysis. (a) Control: virgin hair (0 hours). (b) Exposed (160 hours) to UV radiation. the high resolution of electron microscopy with the environmental and simple flexibility of light microscopy. The dual advantage that AFM affords may render it the ideal choice for studies of roughness, thickness, and any other changes in the topography of hair structure.

EVALUATION OF UV HAIR DAMAGE BY AFM 281 AFM was also successfully employed to investigate the changes in hair surface roughness when hair fibers undergo long-term exposure to UV radiation. By means of the Student t-test, it was possible to prove statistically that the AFM parameters of roughness and surface distance developed in this work, and cuticle thickness, are able to discriminate the two sets of samples--a set of unexposed hair samples and a set of damaged hair samples. ACKNOWLEDGMENTS The authors acknowledge the Brazilian funding support agencies CNPq, RHAE, and FAPESP. REFERENCES (1) E. Tolgyesi, Weathering of hair, Cosmet. Toilerr., 98, 29-33 (1983). (2) E. Hoting et aL, Photochemical alterations in human hair. I. Artificial irradiation and investigation of hair proteins, J. Soc. Cosmet. Chem., 46, 85-99 (1995). (3) S. Ratnapandian, Photodegradation of Human Hair, M.S. Thesis, University of Massachusetts, Amherst, 1997. (4) C. R. Robbins and M. Bahl, Analysis of hair by electron spectroscopy for chemical analysis, J. Soc. Cosmet. Chem., 35, 379-390 (1984). (5) J. B. Speakman and P. R. McMahon, The action of light on wool and related fibers, N.Z.J. Sci. Tech., 20 (1939). (6) L.J. Wolfram, in Hair Research, Status and Future Aspects, Organos, Montagna, and Sturtgen, Eds., 1981, pp. 479-500. (7) S. Wei, Efficts of Graying Process on Hair Properties, M.S. Thesis, Philadelphia College of Textiles and Science, 1995. (8) S. B. Ruetsch, Y. Kamath, and H. D. Weigmann, Photodegradation of human hair: An SEM study, J. Cosmet. Sci., 51, 103-125 (2000). (9) J. A. Swift and J. R. Smith, Atomic force microscopy of human hair, Scanning, 22, 310-318 (2000). (10) L. H. C. Mattoso, F.C. Ferreira, P.S. P. Herrmann, A.R. Martin, M.A. Pereira-Da-Silva, L.G. Paterno, M. A. Piza, A. A. S. Cuvelo, L. A. Coinago, and F. Denes, Atomic force microscopy as a tool for the evaluation of natural fibers and polymers surface, Fifth International Confirence on Woodfiber- Plastic Composites (Madison, Wisconsin, 1999), pp. 43-56. (11) M. L. Tare, Y. K. Kamath, S. B. Ruetsch, and H.-D. Weigmann, Quantification and prevention of hair damage, J. Soc. Cosmet. Chem., 44, 347-371 (1993).