142 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I The Variables and the Calculated o/w Phase-Volume Ratios (4)) of the Thirty-Six HCV 0.2% Emulsions* Formula # % Petrolatum % Mineral oil % Water 1 0 0 78.9 0.06 2 0 10 68.9 0.19 3 0 20 58.9 0.35 4 0 30 48.9 0.57 5 0 40 38.9 0.88 6 0 50 28.9 1.34 7 0 60 18.9 2.10 8 0 70 8.9 3.59 9 10 0 68.9 0.19 10 10 10 58.9 0.35 11 10 20 48.9 0.57 12 10 30 38.9 0.88 13 10 40 28.9 1.34 14 10 50 18.9 2.10 15 10 60 8.9 3.59 16 20 0 58.9 0.35 17 20 10 48.9 0.57 18 20 20 38.9 0.88 19 20 30 28.9 1.34 20 20 40 18.9 2.10 21 20 50 8.9 3.59 22 30 0 48.9 0.57 23 30 10 38.9 0.88 24 30 20 28.9 1.34 25 30 30 18.9 2.10 26 30 40 8.9 3.59 27 40 0 38.9 0.88 28 40 10 28.9 1.34 29 40 20 18.9 2.10 30 40 30 8.9 3.59 31 50 0 28.9 1.34 32 50 10 18.9 2.10 33 50 20 8.9 3.59 34 60 0 18.9 2.10 35 60 10 8.9 3.59 36 70 0 8.9 3.59 * 4) values were calculated from Vo/V,, Vo and V,, are the total volume of oil phase and aqueous phase, assuming the density is equal to 1. (54.5% relative humidity), and potassium sulfate (97% relative humidity). Approxi- mately 30 mg of the test formula was applied on a microscope slide by means of a microdispenser and was spread to an even layer using a cover glass. The microscope slide was then placed on the probe, and the water evaporation rate (WE) was read to the nearest 0.1 g/m2h after it reached the equilibrium state in approximately three to five minutes. Weighing method. This method was based upon the percentage of remaining weight after a given period of time. A piece of glass supported by an iron stand was placed on the

EMULSION VEHICLES AND VASOCONSTRICTOR ACTIVITY 143 Table II Rating Scale of Physical Stability Evaluation Rating scale Physical stability 1 Stable 2 Beginning bleeding 3 Bleeding 4 Beginning separation 5 Separation surface of a water bath (37 --- 0. iøC). Approximately 50 mg of the test formula was weighed on a known weight of aluminum foil (2 cm X 2 cm) and then placed on the glass. The exact weight of the test material was recorded, and then it was reweighed after V2, 1, 2, 3, and 4 hr. This method was only used for the twelve selected formulas in the in vitro skin permeation study and in vivo transepidermal water loss determina- tion. TRANSEPIDERMAL WATER LOSS DETERMINATION (TEWL) The TEWL of the wrist and forearm of human volunteers was determined by means of the evaporimeter. The TEWL of the bare skin was first recorded before the test formula was applied to the spot. The TEWL was read again right after the test material was spread in an even layer using a small spatula, then continuously read every 15 minutes for 1 V2 hr. During measurement, the skin was left open and undisturbed at ambient conditions (23 --- 2øC, 40 ___ 5% RH). TEWL determinations were made only for the selected twelve formulas. COSMETIC ACCEPTANCE EVALUATION The twelve selected formulas were evaluated for their cosmetic acceptance using a self- designed rating system (Table lll). Five males and five females were asked to score the formulas. Color and appearance were judged by looking directly at the formulas in the jar. By rubbing approximately 0.5 gm of the test formula onto the back of the hand, odor, homogeneity, texture, spreadability, and greasiness were evaluated. Homoge- neity was also examined by spreading the formula on a big spatula using another smaller spatula. Finally, washability was scored by washing the applied formula on the hand using warm water (30 --- 3øC). Two-way analysis of variance (ANOVA) was used to analyze the scores obtained for individual and overall characteristics. Whenever the ANOVA results showed that the means were significantly different from each other, the Tukey's Honestly Significant Difference (HSD) test was conducted to obtain more de- tailed information about the differences among the means. This statistical analysis was done using an IBM 4033 computer. PREPARATION OF EXCISED HUMAN SKIN Human skin obtained from autopsy was cleaned of hair and fat with a regular razor blade, scissors, and forceps. The skin was then sectioned by a model 880 freezing microtome (AQ Scientific Instruments, Division of Warner Lambert Tech., Inc., Buf-