SENSITIVE PROBE OF HAIR SURFACE 233 Table II Subjective and Instrumental Assessments of Shampoo Treatments • Subjective rank 2'3 Instrumental shine 3 Shampoo A1 0.762 (0.10) Shampoo A2 0.714 (0.09) SLS 0.696 (0.03) Shampoo C2 0.602 (0.04) Shampoo B2/shampoo C2 0.582 (0.02) Shampoo B2 0.551 (0.08) Shampoo B! 0.486 (0.03) Shampoo B 1/shampoo C 1 O.427 (O.O3) Assessments were made with a minimum of three tresses per treatment. Treatments are listed in order of decreasing shine. Vertical lines connect treatments that are not statistically different. build up with repeated use. As a result of this particle deposition, the shampoos in group 2 all caused dulling. The third type of treatment effect occurred when the negatively charged fatty acid salts in one shampoo formed a complex with the positively charged Polyquaternium-10 previously deposited on the hair by another shampoo. These types of particles caused the greatest degree of dulling on hair. Although only one example of Polyquaternium-10/ myristic acid dulling is shown in Table II (B l/C1), a second example of this type of interaction and shine loss was observed in single-fiber tests between shampoos B2 and C1. The former product contains Polyquaternium-10 in a sodium laureth sulfate de- tergent system. CONCLUSIONS In this paper, goniophotometric measurements of shine were presented and shown to exhibit excellent correlation with a large series of subjective assessments. In addition to providing a quantitative measure of hair shine, the light-scattering methods presented were also shown to serve as a sensitive probe of the hair surface, permitting one to monitor deposition, removal, and even interaction of particles on hair. Employing the light-scattering methods developed, a group of shampoos containing highly substantive ingredients was shown to dull hair as a result of deposition on the fiber surface, while even worse dulling was observed as a result of interaction on the fiber surface of incompatible particles from different shampoos. It should be noted that the incidence and magnitude of dulling effects from deposition depends on the size of the particles deposited on the hair surface (14). The greatest degree of diffuse scattering and, consequently, the greatest degree of dulling, occurs from particles of the order of 0.4 to 0.7 microns. Particles of the order of 4 microns or larger, on the other hand, will reflect light specularly. Thus, although the substantive ingredients in the shampoos tested in this work caused dulling, it is conceivable that substantive ingredients from other products might be

234 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS deposited in the form of a film. Depending upon the orientation of its various parts, such a film might cause little or no dulling and, in fact, might even increase hair shine. ACKNOWLEDGMENTS We are grateful to Mr. Frank Schebece of Colgate-Palmolive, who performed the modification of the Brice-Phoenix photometer and also provided us with many useful suggestions. Most of the tress experiments were performed by Ms. Donna Hartnett and Ms. Judy McKendrick. REFERENCES (1) R. F. Stature, M. L. Garcia, and J. J. Fuchs, The optical properties of human hair. 1. Fundamental considerations and goniophotometer curves, J. Soc. Cosmet. Chem., 28, 571-599 (1977). (2) R. F. Stature, M. L. Garcia, and J. J. Fuchs, The optical properties of human hair. II. The luster of hair fibers,.]. Soc. Cosmet. Chem., 28, 601-609 (1977). (3) A. Guiolet, J. C. Garson, and J. L. Leveque, Study of the optical properties of human hair, Int. J. Cosmet. Sci., 9, 111-124 (1987). (4) 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). (5) W. J. Conover, Practical Nonparametric Statistics, 2nd ed. (John Wiley & Sons, New York, 1980), pp. 299-300. (6) R. Jeffries, Measurement of the extent of delustring of filament fabrics. Part I. Description of instrument and method of measurement,.]. Text. Inst., 46, T319-T328 (1956). (7) J. S. Christie, An instrument for the geometric attributes of metallic appearance, Appl. Opt., 8, 1777-1785 (1969). (8) B. J. Tighe, "Subjective and Objective Assessment of Surfaces," in Polymer Surfaces, D. T. Clark and W. J. Feast, Eds. (John Wiley & Sons, Chichester, 1978), pp. 269-286. (9) D. Nickerson, A raw cotton lustermeter for yarns and fabrics, Text, Res. J., 27, 111-123 (1957). (10) L. E. Holboke and L. P. Berriman, A study of the effect of cotton fiber structure on luster, Text. Res. J., 33, 205-217 (1963). (11) C. R. Robbins, Chemical and Physical Behavior of Human Hair, 2nd ed. (Springer-Verlag, New York, 1988), pp. 273-274. (12) R. J. Crawford and C. R. Robbins, A replacement for Rubine dye for detecting cationics on keratin, J. Soc. Cosmet. Chem., 31, 273-278 (1980). (13) W. Mendenhall, Introduction to Probability and Statistics (Duxbury Press, Boston, 1983), pp. 630-634. (14) D. B. Judd and G. Wyszecki, Color in Business, Science, and Industry, 2nd ed. (John Wiley & Sons, New York, 1963), p. 381.