10 JOURNAL OF COSMETIC SCIENCE Aqueous phase: Carbomer 1382 triethanolamine (TEA) distilled water. So/at filters: Isoamyl-p-methoxycinnamate (Heliopan E- 1000), butylmethoxydibenzoyl- methane (Parsol 1789). Preservative: Nipaguard: a mixture of sodium propyl and methyl hydroxybenzoate, 2-phenoxyethanol, and 2-bromo-2-nitropropane-l,3-diol. This combination is a specific preservative for solar filters. So/vent: Alcohol benzoic C12_15 (Finsol VTN). Formulation composition: Isoamyl-p-methoxycinnamate 7 % B utylmethoxydibenzoylmethane 1.5 % DC-244 (tetramer silicone) 4% Silbione V-5 (pentamer silicone) 4% Alcohol benzoic C12_15 4% Nipaguard BPX 0.5 % Triethanolamine 0.8 % DC- 1401 (dimethiconol) 3 % Carhomer 1382 0.7% Distilled water 78% FORMULA PREPARATION The galenical formulation was prepared by using the cold emulsifying technique (6-8), consisting, in this instance, of the following steps: 1. The sunscreens are mixed with the solvent. The preservative and the mixture of cyclomethicones are then added, followed by the carbomer, water, and TEA. Finally, dimethiconol is added and the emulsion is homogenized. 2. In the elevated-temperature preparation technique, the aqueous and the oily phases are raised to a temperature of about 60øC before mixing them together. 3. The preparations are heated to 40-60øC and centrifuged to study their stability, in accordance with commonly used stability test method. MICROPHOTOGRAPHIC STUDY Droplet size is expressed as the size of globules in the internal phase and depends on the type and amount of surfactant, the technique of emulsification, the order in which components are added, etc. Microphotography is an extremely useful technique in stability studies as it allows determination of such factors as creaming, coalescence, and recrystallization processes (9,10). A Lavobal H, Carl Zeiss Jena microscope equipped with a camera was used in this study (11). Photographs were taken of samples kept at room temperature, at 40øC, and at 60øC, as well as of samples that were centrifuged. RESULTS AND DISCUSSION There was scarcely any difference in the organoleptic characteristics of the formulations prepared at room or at elevated temperature, although over time the ones prepared at room temperature seemed to have slightly greater stability parameters. This fact, com- bined with their ease of preparation, comprises a clear advantage.

SILICONE-BASED EMULSION GELS 11 Figure 1. The sample prepared at room temperature. Figure 2. The sample prepared at elevated temperature.