SILICONE-BASED SUNSCREENS 385 % RELEASED FILTER % RELEASED FILTER 100 100 80- 60- 40- 20- 0.25 0.5 0.75 1 1.25 2.75 24 TIME (hours) ß 310 rim. • 359 nm. Figure 9. Percentage of filters released by the formulation as a function of time. WASH-OFF TESTS Because the formulation was designed as a sunscreen, wash-off tests (13,14) were nec- essary to ensure that the silicones provided adequate substantiveness to the preparation. For 24 h, samples were subjected to a water flow at 25øC. The percentage of solar filter released from the sample after different times is shown in Figure 9. After 24 h (i.e., much longer than under conditions of normal use), approximately 40% of Parsol 1789 and 60% of Heliopan E-1000 had been lost from the formulation. This result indicates that a significant proportion of the filter remains on the skin even after repeated bathing. ACKNOWLEDGMENTS We thank Karen Shashok for translating the original manuscript into English. REFERENCES (1) J. Smid-Korbar, J. Kristl, and M. Stare, Efficiency and usability of silicone, surfactants in emulsions, Int. J. Cosmet. Sci., 12, 135-139 (1990). (2) M-•A. Ruiz, A. Hernlndez, A. Parera, and V. Gallardo, Dimethylsiloxane polymers: Vaporization rate test/freezing temperatures,J. Soc. Cosmet. Chem., 46, 175-180 (1995). (3) A.J. Disapio and M. S. Starch, New silicones emulsifier technology, Cosmet. Toilerr., 96, 55-57 (1981). (4) C. Willemin, Param•tres de solubilit& Caract•risation et selection des silicones, Parf•ms, Cosmetiq•es, Arames, 102, 75-78 (1992). (5) C. Cabeza, Derivados organomodificados de silicona, Noticias de cosmdtica y perfamer/a, 173, 17-24 (1990).

386 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (6) (7) (8) (9) (10) (11) (12) (13) (14) G. Backer and D. Ghirardi, Meeting the trend towards non greasy cosmetic products with silicone technology. Cosmetics Conference, London, 1993. Unique formulas for success. A guide to formulating with silicones. Dow Corning Corp., 1990. Merck-Igoda, Conceptos b•sicos sobre la protecci6n contra rayos UV en cosm•tica, Noticias de cosmdtica y perruiner/a, 184, 14-20 (1992). H. Brown, Sunscreens need vehicles, Cosmet. Toiletr., 101, 51-54 (1986). Real Decreto 1415/1995 of 14 September (B.O.E., num. 220). F. Puisieux and M. Seiller, Galdnica (5). Les Systbnes di3persfi' (Technique et Documentation, Lavoisier, Paris, 1983), pp. 444-450. L. Niemi, Influence of ageing on hydrocortisone particles in O/W creams, Acta Pharm. Nord., 1, 259-268 (1989). P. Treffel, B. Gabard, and R. Juch. Evaluation of barrier creams: An in vitro technique on human skin, Acta Derre. Venereol, 74, 7-11 (1994). L. Niemi and P. Kahela, Effect of water content and type of emulgator on the release of hydrocortisone from O/W creams, Acta Pharm. Nord., 1, 391-396 (1989).