REGENERATION OF NMF 29 These studies confi rm the conclusions previously drawn (14) as to the effects of soaking on the NMF that is to say, a simple ten-minute fresh-water soak can remove signifi cant amounts of the free amino acid components of the stratum corneum. No clear correlation was observed between NMF levels and skin hydration as measured by the MAT, but it appears likely that NMF (as free amino acid levels) relates to SC pH. These results are consistent with studies showing that hydration measurements relate mainly to extremely superfi cial layers of the SC (21), from which the NMF has already been almost completely lost and cannot be replaced without shedding of the uppermost cells. Our results confi rm that SC recovery to its baseline condition after soaking is relatively slow and complex in its kinetics. ADDITIONAL INFORMATION Complete numerical NMF data are available by correspondence. ACKNOWLEDGMENTS This work was supported by an SCC Graduate Fellowship. REFERENCES (1) A. M. Kligman, in Bioengineering of the Skin: Water and the Stratum Corneum, P. Elsner, K.-P. Wilhelm, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 251–255. (2) D. W. Ramsing and T. Agner, Contact Dermatitis, 34, 258–262 (1996). (3) T. F. Tsai and H. I. Maibach, Contact Dermatitis, 41, 311–314 (1999). (4) R. R. Warner, K. J. Stone, and Y. L. Boissy, J. Invest. Dermatol., 120, 275–284 (2003). (5) A. M. Allen and D. Taplin, Lancet, 1185–1189 (1973). (6) I. Willis, J. Invest. Dermatol., 60, 166–171 (1973). (7) I. M. Stender, C. W. Blichmann, and J. Serup, Clin. Exp. Dermatol., 15, 206–209 (1990). (8) E. Berardesca, G. P. Vignoli, F. Distante, P. Brizzi, and G. Rabbiosi, Contact Dermatitis, 32, 83–87 (1995). (9) W. K. Loke et al., J. Appl. Toxicol., 19, 285–290 (1999). (10) R. Gfatter, P. Hackl, and F. Braun, Dermatology, 195, 258–262 (1997). (11) Y. Hatano et al., J. Invest. Dermatol., 129, 1824–1835 (2009). (12) E. H. Choi et al., J. Invest. Dermatol., 127, 2847–2856 (2007). (13) K. P. Ananthapadmanabhan et al., Int. J. Cosmet. Sci., 25, 103–112 (2003). (14) M. O. Visscher, G. T. Tolia, R. R. Wickett, and S. B. Hoath, J. Cosmet. Sci., 54, 289–300 (2003). (15) R. R. Wickett, G. Tolia, B. Fugitt, M. O. Visscher, and S. B. Hoath, Bioengineering evaluation of the water handling capacities of stratum corneum in vivo, Proc. 2001 IFSCC Intl. Conf., Taipei, Taiwan, 37–46 (2001). (16) G. B. Jemac and J. Serup, Acta Derm. Venereol. (Stockh.), 70, 245–247 (1990). (17) P. Treffel and B. Gabard, Arch. Dermatol. Res., 287, 474–479 (1995). (18) I. R. Scott, C. R. Harding, and J. G. Barrett, Biochim. Biophys. Acta, 719, 110–117 (1982). (19) P. M. Krien and M. Kermici, J. Invest. Dermatol., 115, 414–420 (2000). (20) P. G. M. van der Valk, M. Kucharekova, and R. A. Tupker, in Bioengineering of the Skin: Water and the Stratum Cornuem, J. Fluhr, P. Elsner, E. Berardesca, and H. I. Maiboch, Eds. (CRC Press, Boca Raton, FL, 2004), pp. 97–104. (21) L. Brancaleon, M. P. Bamberg, T. Sakamaki, and N. Kollias, J. Invest. Dermatol., 116, 380–386 (2001).

J. Cosmet. Sci., 61, 31–38 (January/February 2010) 31 Modeling the time-dependent water wave stability of human hair F.-J. WORTMANN, M. STAPELS, and L. CHANDRA, Textiles & Paper, School of Materials, University of Manchester, PO Box 88, Manchester M60 1QD, UK (F.-J.W.), DWI e. V. and ITMC, RWTH Aachen, Pauwelsstrasse 8, D-52056 Aachen, Germany (M.S.), and Unilever R&D, Port Sunlight, CH63 3JW Wirral, UK (L.C.). Accepted for publication June 15, 2009. Presented in specifi c parts at the 3rd International Conference on Applied Hair Science, TRI Princeton, September 15–16, 2008. Synopsis The viscoelastic bending recovery of human hair is described by a hydro-rheologically complex, two-phase model, where the humidity dependence of the pertinent parameters as well as the effects of physical aging are known. Model calculations are conducted to assess the consequences of the time- and humidity-dependent bending recovery of human hair for the formation and the stability of the water wave. It is shown that a hair fi ber that has been set in bending will achieve at 65% RH a recovery of about 50% after about ten times its storage time prior to release, if it is a non-aging material. However, aging drastically slows the recovery pro- cess so that it approaches an apparent “equilibrium,” fi nal recovery value of about 60%. The values of fi nal recovery decrease linearly with water content, vanishing as expected at maximum water content, where the hair fi ber is above its glass transition. The calculations further show that damage to the elastic modulus, attributed to the intermediate fi laments, is expected to reduce recovery and thus enhance fi ber set. The cal- culations demonstrate that it is in fact the phenomenon of physical aging that makes water waving a feasible and practically successful process for hair styling. INTRODUCTION In a recent investigations (1) we considered the recovery of human hair from bending deformation in an experimental context related to the formation and stability of a water wave. The bending recovery behavior was determined for a range of humidities and aging times and comprehensively analyzed on the basis of a two-phase fi lament/matrix model representing the complex morphology of hair. In this model the intermediate fi laments (IF) (2), or rather their α-helical fraction, are identifi ed as the fi lamentous phase in hair. The matrix in consequence contains as major components the amorphous IF-associated proteins (IFAP) (3) and also summarily the rest of the morphological components, such as cuticle, cell membrane complex, etc. (4). Address all correspondence to F.-J. Wortmann. The current address of M. Stapels is Kao Chemicals Gmbh, D-46446, Emmerich, Germany.