MOISTURE MASKS AND CHITOSANS 7 Table IV Effect of Adding Different Molecular Weights and Concentrations of Water-Soluble Chitosans on the Parameters of the Power Law Models of Moisture Masks at 23 ø _+ 0.2øC U3 chitosan U30 chitosan U120 chitosan Concentration (%) K n K n K n Control 3.417,** 0.51 a,, 0.50 4.325 0.46 b 4.215,6 0.48a,b 4.116 0.50 • 0.75 4.623 0.42 c'd 4.43 ¸ 0.45 c,• 4.335 0.47 s 1.00 6.79 • 0.36 e 5,972 0.39 d'• 4.533'4 0.42 • K: consistency index n: flow behavior index. * a-e values (n = 3) followed by the same superscript within the same column are not significantly different (p 0,05 by Duncan's multiple-range test). ** 1-7 values (n = 3) followed by the same superscript within the same column are not significantly different (p 0.05 by Duncan's multiple-range test). U3, U30, and U120 chitosan: the same as in table I. consistency indexes (Table IV) or the apparent viscosities (Table III) of the moisture masks increased with the increasing molecular weight of chitosans used (of the same concentration of water-soluble chitosans used). The apparent viscosities of moisture masks containing 2% methyl cellulose were lower than those of masks containing 0.5% U3 chitosan. COLOR OF MOISTURE MASKS Absorbance at 490 nm of moisture masks was used as an index of color. Results in Figure 2 show that absorbances of moisture masks at 490 nm increased from 0.01-0.02 to 0.06-0.08 with increasing concentrations of water-soluble chitosans in the formula from 0.5 % to 2.0%. Using water-soluble chitosans of different molecular weights (at the same concentration) produced no significant differences in the absorbances of moisture masks. SAFETY OF MOISTURE MASKS Table V shows the effect of adding different molecular weights and concentrations of water-soluble chitosans on the pH and safety (Draize score) of moisture masks. Draize scores of all moisture masks containing water-soluble chitosans (0.5%-2%) were zero. The results indicate that moisture masks containing water-soluble chitosans resulted in no erythema on shaved rabbit skin. The pHs of those moisture masks ranged between 6.2 and 6.5 and are close to the normal pH of human skin. THE EFFICACY OF MOISTURE MASKS IN TERMS OF WATER-HOLDING CAPACITY Figure 3 shows the changes of electrical capacitance increase ratio with time after application of moisture masks containing 2% different molecular weight water-soluble chitosans and 2% methyl cellulose (control) measured at 23 ø + 0.2øC and 60% RH. After applying moisture masks containing different molecular weight water-soluble

8 JOURNAL OF COSMETIC SCIENCE 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 0.5 1 1.5 2 2.5 Concentration (%) Figure 2. Effect of adding different molecular weights and concentrations of water-soluble chitosans on the absorbance (490 nm) of moisture masks (MW: ', 2.42 x 10 6 Da I, 1.62 x 10 6 Da &, 1.17 x 10 6 Da). chitosans or methyl cellulose (86,000 Da), the electrical capacitance increase ratio in- creased to 60%-65%, then decreased, and finally leveled off. Electrical capacitance increase ratios after 60 min were 38%, 34%, and 31% for moisture masks containing 2% U3 chitosan, 2% U30 chitosan, and 2% U120 chitosan, resprectively. The electrical capacitance of the moisture mask containing water-soluble chitosans was significantly higher than that of the mask containing 2% methyl cellulose, which had an electrical capacitance increase ratio of 26% after 60 min. Table V Effect of Adding Different Molecular Weights and Concentrations of Water-Soluble Chitosans on the pH and Safety of Moisture Masks Concentration (%) Draize score pH Control 0* 6.5-6.7 U3 chitosan O.5 0 6.3-6.5 1.0 0 6.3-6.5 2.0 0 6.3-6.5 U30 chitosan 0.5 0 6.2-6.5 1.0 0 6.2-6.5 2.0 0 6.2-6.5 U120 chitosan O.5 0 6.3-6.5 1.0 0 6.3-6.5 2.0 0 6.3-6.5 * Draize score of 0 indicates no erythema. U3 chitosan, U30 chitosan, and U120 chitosan: the same as in Table I.