JOURNAL OF COSMETIC SCIENCE 132 Figure 9. The effect of pH on fi lm hardness. Figure 10. The effect of pH on fi lm hardness. dispersion during pre-formulation, and enables them to select softer or harder poly- mers—or a blend of both—for a balanced system. 3. Our experiments showed a modifi cation of fi lm hardness under the several factors such as pigment interaction, adjusting the pH of the polymer, adding surfactant (high or low HLB), and the effect of temperature. 4. The experiments allowed us to differentiate a suitable emulsion system to achieve the desired properties of the polymer.

2008 TRI/PRINCETON CONFERENCE 133 5. The neat polymer may not exhibit the hardness desired, but may be more appealing when subjected to heat or blended with typical formulation ingredients (surfactants, pigment), as can be seen with Sample G. 6. More data need to be compiled on polymers with similar technology in order to better understand the correlation between fi lm hardness and the performance of the fi nal product, especially the effect of different pH adjusters on fi lm hardness as well as the effect of various emulsifi ers. 7. The hardness test does not necessarily correlate with mascara performance, but it helps to defi ne the formulation approaches and better understanding of polymer performance in a mascara formula. All of these factors, and their effect on the fi nal formulation, continue to be investigated in our laboratory. ACKNOWLEDGMENTS The authors are grateful to Coty’s Nail Lab personnel sharing their experience in fi lm hardness determination and appreciate Rossana Lanza’s participation in this study as well as all volunteers who participated in the study. REFERENCES (1) A. Prada, Experimental Study of the Effectiveness of Gels for Profi le Modifi cation (Master’s Thesis, The Univer- sity of Oklahoma, Norman, Oklahoma, 1998). (2) J. E. Glass, Water Soluble Polymers: Beauty with Performance (Advances in Chemistry Series 213), (Ameri- can Chemical Society, Washington, D.C., 1986). (3) C. R. Robbins, Chemical and Physical Behavior of Human Hair, 3rd ed. (Springer, New York, 1994). (4) C. R. Robbins and M. J. Bhal, Analysis of hair by electron spectroscopy for chemical analysis, J. Soc. Cosmet. Chem., 35, 379–390 (1984). (5) C. Zviak. The Science of Hair Care (Marcel Dekker, New York, 1986).