HUMAN HAIR MOISTURIZATION WITH COSMETIC PRODUCTS 319 swollen hair–water composite. A method has been developed to convert simple hysteresis data into a hysteresis ratio HR which can quantify the ability of hair treated with products and processes to retain (or repel) moisture as compared with the corresponding untreated hair. Work described in this communication shows that cross-linking with heat is more effective in retaining moisture as compared with rinse-off conditioning actives. The work described in this communication can be used to evaluate “moisturizing” or “anti- moisturizing” actives and products. Such information will be useful for formulators. The nature of sorption of water into the hair substrate has been considered from a molecular perspective. Swelling of the sorbent has a major effect on the measurement of pore vol- ume and surface area by the BET method. This analysis clearly shows that a large fraction of water is held in larger pores and is not accounted for by the BET analysis. This creates a discrepancy between the results of BET analysis by gas (nitrogen or carbon dioxide) adsorption and the DVS results obtained with sorption of water. Using carefully prepared hair samples, we have been able to show the effectiveness of DVS method in quantifying effi cacy of cosmetic formulations and processes with a limited number of experiments where the effects were robust. In the case of weak effects, adequate number of replicates will be necessary to establish statistically signifi cant outcomes. AC KNOWLEDGMENTS So me of the work reported in this communication was performed during the late nineties by Dr. Cordula Wilrich and Amy Lyttle at TRI/Princeton. The author gratefully acknowl- edges their contribution. Also, the author is thankful to Dr. David Graham, President of TRI for permission to publish this paper. RE FERENCES ( 1 ) C. R. Robbins, Chemical and Physical Behavior of Human Hair, 3rd Ed. (Springer-Verlag, New York, NY, 1994), pp. 23–28. ( 2 ) C. C. Wagner, P. K. Kiyohara, M. Silveira, and I. Joekes, Electron microscopic observations of human hair medulla, J. Microsc., 226, 54–63 (2007). (3 ) Nagase, S. Shibuichi, K. Ando, E. Kariya, and N. Satoh, Infl uence of structure of hair fi ber on hair ap- pearance. I. Light scattering from the porous structure of the medulla of human hair, J. Cosmet. Sci., 53, 89–100 (2002). ( 4 ) W. P. Bryan, Sorption hysteresis and the laws of thermodynamics, J Chem. Educ., 64, 209–212 (1987). ( 5 ) S. Rosenbaum, Solution of water in polymers: the keratin-water isotherm, J. Polym. Sci., C31, 45–55 (1970). ( 6 ) Y. K. Kamath, H.-D. Weigmann, and C. J. Dansizer, Surface wettability of human hair, Part 1: effect of deposition of polymers and surfactants, J. Appl. Polym. Sci., 29, 1011–1026 (1984). ( 7 ) W. J. Moore, Physical Chemistry, 3rd Ed. (Prentice-Hall, Englewood-Cliffs, NJ, 1964), p. 191. ( 8 ) S. B. Ruetsch and Y. K. Kamath, Penetration of cationic conditioning compounds into hair fi bers, J. Cosmet. Sci., 56, 323–330 (2005). ( 9 ) K. Keis, C. L. Huemmer, and Y. K. Kamath, Effect of oil fi lms on moisture vapor absorption on human hair, J. Cosmet. Sci., 58, 135–145 (2007). (1 0 ) W. J. Moore, Physical Chemistry, 3rd Ed. (Prentice-Hall, Englewood-Cliffs, NJ, 3rd Edition, 1964), Vol. 964, pp. 341–343. (11) S. Ross and I. D. Morrison, Colloidal Systems and Interfaces (John Wiley & Sons, New York, NY, 1988), pp. 50–53. (12) F. Thielmann, D. Pearce, and Y. Kamath, The characterizationof surface area and surface heterogeneity profi les of hair by inverse gas chromatography, IFSCC Mag., 5, 189–193 (2002).

JOURNAL OF COSMETIC SCIENCE 320 (13) Y. Z. Hessefort, B. T. Holland, and R. W. Cloud, The porosity measurement of hair: a new way to study hair damage mechanisms, J. Cosmet. Sci., 59, 303–315 (2008). (14) T. Gao, Y. He, P. Landa, and J. M. Tien, Study of hair surface energy and conditioning, J. Cosmet. Sci., 62, 127–137 (2011). (15) J. A. Swift, “Morphology and histochemistry of human hair,” in Formation and Structure of Human Hair, P. Jolles, H. Zahn, and H. Hocker, Eds. (Birkhauser Verlag, Boston, MA, 1997), pp. 165–170. (16) J. W. Rowen and R. L. Blaine, Sorption of nitrogen and water vapor on textile fi bers, J. Res. Natl. Bur. Stand., 39, 479 (1947). (17) M. Spei and H. Zahn, X-ray Small-Angle Examination of Swollen Fibre Keratins, Melliand Textilber., 60, 523 (1979). (18) Y . Kamath, N. S. Murthy, and R. Ramaprasad, Preiminary analysis of the distribution of water in human hair by small angle neutron scattering, J. Cosmet. Sci., 65, 37–48 (2014).