RHEOLOGICAL CHANGES IN COSMETICS 333 investigated with two different probes (block-type and roller-type). With the block-type probe, the spreading change of massage gels was clearly related to the detected frictional force, which correlated with the sample viscosity. On the other hand, the stickiness properties of cosmetics were well reflected in the force detected with the roller-type probe. The frictional force at the steady state correlated with the post-application stickiness, as well as spreading or absorption during application, and richness or hydra- tion after application. We conclude that this measuring device can provide useful information for the development of cosmetic formulations. REFERENCES (1) L. B. Aust, L. P. Oddo, J. E. Wild, O. H. Mills, andJ. S. Deupree, The descriptive analysis of skin care products by a trained panel of judges,.]. Soc. Cosmet. Chem., 38, 443-449 (1987). (2) A. H. F•3rster and T. M. Herrington, Rheology of two commercially available cosmetic oil in water emulsions, Int. `]. Costa. Sci., 20, 317-318 (1998). (3) S. Wang, M.S. Kislalioglu, and M. Breuer, The effect of theological properties of experimental moisturizing creams/lotions on their efficacy and perceptual attributes, Int. `]. Costa. Sci., 21, 167-188 (1999). (4) R. Bruinruer and S. Goriersky, Rheological studies to objectify sensations occurring when cosmetic emulsions are applied to the skin, Colloid. Surf A, 152, 82-94 (1999). (5) K. Masaki and N. Totani, The evaluation of oily components by using the frictional feel analyzer, `].Soc. Cosmet. Chem. `]pn., 32, 59-64 (1998). (6) K. Suganuma and M. Niwa, Relation between physical property of massage creams and skin surface smoothness,.]. Soc. Cosmet. Chem.`]pn., 23, 212-219 (1991). (7) I. Iida, H. Nishimura, Y. Ikeyama, and T. Koyanagi, Studies on typification of cosmetics-- Relationship between sensory evaluation and physical measurement of emulsions,`]. Soc. Cosmet. Chem. `]pn., 23, 295-300 (1990). (8) T. Nomura, K. Suzuki, R. Suzuki, and Y. Kajiwara, A newly-developed tactile sensor and its appli- cation to the evaluation of cosmetics,`]. Soc. Cosmet. Chem. `]pn., 31, 79-81 (1997). (9) J. K. Prall, Instrumental evaluation of the effects of cosmetic products on skin surfaces with particular reference to smoothness,`]. Soc. Cosmet. Chem., 24, 693-707 (1973). (10) A. F. El-shimi, In vivo skin friction measurements,`]. Soc. Cosmet. Chem., 28, 37-51 (1977). (11) H. Tanimoto and M. Nashimoto, Evaluation of cosmetic effects with a friction meter, Cosmet. Toiletr., 94, 20-24 (1979). (12) S. Nacht, J. Close, D. Yeung, and E. H. Gans, Skin friction coefficient: Changes induced by skin hydration and emollient application and correlation with perceived skin feel,`]. Soc. Cosmet. Chem., 32, 55-65 (1981). (13) M. Lod•n, H. Olsson, L. Skate, and T. Ax•11, Instrumental and sensory evaluation of the frictional response of the skin following a single application of five moisturizing creams,`]. Soc. Cosmet. Chem., 43, 13-20 (1992). (14) M. Date and I. Inaba,`]apanese Patent No. 3023142 (Japanese Patent Office, June 8, 1990). (15) u. Zeidler, The spreading of lipids on the skin, Fette Seij•n Anstrichmittel, 87, 403-408 (1985). (16) B. A. Salka, Choosing emollients, Cosmet. Toiletr., 112, 101-106 (1997).

j. Cosmet. sci., 54, 335-351 (July/August 2003) Optical properties of hair: Effect of treatments on luster as quantified by image analysis R. McMULLEN and J. JACHOWICZ, International Specialty Products, Wayne, NJ 07470. Accepted for publication August 19, 2002. Synopsis Image analysis has been employed to measure the luster of hair simulated by light reflected from a curved hair tress. Hair samples (up to four) were mounted side-by-side in a special sample holder in the form of a cylinder and illuminated by a uniform beam of white light. Digital images of hair tresses were captured with a high-resolution camera and were analyzed by scanning across highlighted and dark areas of the resultant image using image analysis software with developed macros. Plots, similar to goniophotometric scattering curves, were used to calculate luster values according to previously published work by Nickerson, Stamm, and Reich-Robbins. Both the Stamm and Reich-Robbins approaches were found to give similar results, while the Nickerson gloss parameter exhibited less sensitivity to hair modification with cosmetic ingredi- ents. The procedure was employed to assess the luster of natural white, light blonde, light brown, medium brown, and dark brown hair, and revealed an increase in luster indices in proportion to an increase in fiber pigmentation. Cosmetic oils such as phenyl trimethicone, amodimethicone, and castor oil were also found to increase the luster of hair as a result of the change in contrast between specular and diffuse reflection. Styling resins such as butyl ester of PVM/MA copolymer, vinyl caprolactam/PVP/dimethylaminoethyl methacrylate copolymer, and isobutylene/ethylmaleimide/hydroxyethylmaleimide copolymer were shown to increase hair gloss by a similar mechanism, as evidenced by calculated higher values of the Stamm and Reich-Robbins luster parameters. An effect of hair dulling by deposition of micronized ZnO at various concentrations, as well as by synthetic sebum, is also discussed. INTRODUCTION The attribute of hair luster has been of significant concern to the consumer and mar- keters for quite some time, especially recently because of the proliferation of reactive and damaging hair treatments. Luster is commonly defined as the ability of a given material to produce a bright reflection. A quantitative analysis of luster and comparison with theoretical models was carried out as recently as the seventies by Stammet al. (1,2). In the last twenty years there have been a number of studies published in this area that employed improved instrumentation. Stammet al. (1,2) employed a goniophotometer and multiple fibers to record the light distribution curves necessary to calculate luster parameters. This work was later expanded by Czepluch et al. (3), who constructed a computerized goniophotometer. Reich and Robbins (4) and Bustard and Smith (5), who also utilized a goniophotometer, employed single fibers to study the effects of sham- 335