2008 TRI/PRINCETON CONFERENCE 95 These observations suggest that the presence of oil in recovered cavities prevents the oc- currence of cuticle cell lifting at alkaline pHs by the combined action of the two follow- ing mechanisms, namely: (a) by the oil acting as a hydrophobic barrier that decreases rapid swelling stresses as water diffuses into the cuticle cells, and (b) by the oil acting as a weak adhesive cement between two separate cuticle cells. The action of both mecha- nisms seems necessary to explain the reduction in cuticle cell lifting at alkaline pHs. For instance, the presence of oil in the recovered cavities or gaps acts as a barrier that decreases steep gradients of swelling. However, eventually the cuticle cells swell and reopen again if the oil does not provide enough adhesion between cuticle cells. CONCLUSIONS The experimental results discussed in the previous paragraphs indicate that the analysis of gap and microcavity formation in cuticle cells by light interference techniques can yield important information when water and oil are allowed to penetrate into these defects. Gaps and microcavities produced by reversible deformations were seen to close by a plasticization effect induced by water. However, the phenomenon of gap and cavity closing alone did not prevent the cuticle cells from reopening again when the hair fi bers were immersed in water at alkaline pHs. In contrast, when the phenomenon of cavity closing by water plasticization was combined with oil penetration, the degree of cuticle cell reopening was substantially reduced. Water penetrates into the cuticle cells and allows for recovery of the protein struc- ture by plasticization. However, water penetration also induces swelling stresses that buckle the cuticle cells if they are decemented. The protective role of oils or lipids may arise, thus, from their capacity to act as a barrier preventing rapid diffusion of water and swelling, and also from their ability to produce a weak adhesion at cuticle cell junctions. REFERENCES (1) C. R. Robbins, Chemical and Physical Behavior of Human Hair , 4th. ed. (Springer-Verlag, New York, 2002), pp. 211–206. (2) J. A. Swift, “The Hair Surface,” in Hair Research, Orfanos Montagna, Ed. (Stuttgen-Springer-Verlag, New York, 1994), pp. 211–226. (3) S. B. Reutsch and H. D. Weigmann, Mechanism of tensile stress release in the keratin fi ber cuticle I, J. Soc. Cosmet. Chem., 47, 13–26 (1996). (4) M. Gamez-Garcia, Patterns of light interfernce produced by damaged cuticle cells in human hair, J. Cosmet. Sci., 58(4), 269–282 (2007). (5) S. Nagase, S. Shibuichi, K. Ando, E. Kariya, and N. Satoh, Infl uence of internal structures of hair fi ber on hair appearance. I. Light scattering from the porous structure of the medulla of human hair, J. Cosmet. Sci., 53(2), 89–100 (2002). (6) M. Gamez-Garcia, Cuticle decementation and cuticle buckling produced by Poisson contraction on the cuticular envelope of human hair, J. Soc. Cosmet. Chem., 49, 213–222 (1998). (7) M. Gamez-Garcia, The cracking of human hair cuticles by cyclical thermal stresses, J. Soc. Cosmet. Chem., 49, 141–153 (1998). (8) M. Yoshinori, N. Hirofumi, and I. Genji, Characterization of the lipid composition at the proximal root regions of human hair, J. Cosmet. Sci., 56(1), 1–16 (2005). (9) M. Feughelman, Mechanical Properties and Structure of Alpha-Keratin Fibers: Wool, Human Hair and Related Fibres, University of New South Wales Press, 1997. (10) S. B. Hornby, Y. Appa, S. Ruetsch, and Y. Kamath, Mapping penetration of cosmetic compounds into hair fi bers using time of fl ight secondary ion mass spectroscopy (TOF-SIMS), IFSCC Magazine, 8, 99– 104 (2005).

J. Cosmet. Sci., 60, 97–109 (March/April 2009) 97 The behavior of hair from different countries CRYSTAL E. PORTER, FELICIA DIXON, CHO-CHO KHINE, BRADFORD PISTORIO, HAROLD BRYANT, and ROLAND de la METTRIE, L’Oréal USA— L’Oréal Institute for Ethnic Hair and Skin Research, Chicago, IL (C.E.P., F.D., C.-C.K., B.P., H.B.), and L’Oréal Recherche, Rio de Janiero, Brazil (R.d.l.M.). Synopsis The properties of curly hair from different countries were assessed using geometrical measurements from a laser scanning micrometer and a new hair shape classifi cation method. In addition, tensile tests, 2-D gel electrophoresis, and differential scanning calorimetry (DSC) were performed. Results concluded that hair characteristics are infl uenced by the degree of curl. For example, curlier hair tended to be more fragile. Inter- estingly, the degree of curl in hair also was dependent upon the country of origin. DSC and 2-D gel electro- phoresis showed that the thermal behavior and the protein markers in hair differed as a function of hair origin. The variability seen in hair characteristics may potentially infl uence how the hair responds to treat- ment and these differences could be caused by regional and cultural diversities in the population from where the hair originated. INTRODUCTION Interest in ethnic hair is growing in the cosmetic science fi eld and a number of researchers have reported on the effect of hair type on hair characteristics that pertain to cosmetic attributes such as visual appearance, manageability and response to treatment (1–4). Keis et al. studied macroscopic characteristics of hair from different ethnic groups to under- stand how ethnicity infl uenced luster (1). They showed that variables such as fi ber diam- eter, cross-sectional shape, and curvature had an impact on luster. Thus, products to modify these characteristics can be considered when enhancing the visual appearance of hair. Garcia and Diaz have shown that the manageability of African-American hair is more challenging compared to Caucasian hair because the increased degree in curl makes it necessary to use much more force during combing (3). Appropriate surface-enhancements and hair assembly treatments and processes can overcome combing obstacles and thus, manageability can be increased. Researches have also found that hair type can infl uence how the hair responds to treat- ments (4). This is particularly important as it pertains to hair from people of African descent because of its inherent fragility compared to people of other races. In addition, there are hair styles and treatments, such as braids and relaxers, that are common within