29 TESTING OF HAND CREAMS The hand cream was centrifuged at high speed for 30 min, and no delamination was observed. The viscosity change rate was less than 0.61%, and the pH value change rate was less than 0.40%, which indicates good centrifugal stability. The thermal stability of the product was tested as described in the emulsion stability test section. After 7 d of thermal cycling, no oil-water separation was observed in the three product samples tested (Table XI). The viscosity change rate was less than 0.08%, and the pH value change rate was less than 0.80%, which indicates good thermal stability. Evaluation of sensory and skin care efficacy. According to the evaluation requirements in the evaluation of sensory and skin care efficacy section of the experimental methods section, 30 volunteers (classmates, 20–25 y) were selected for sensory evaluation after using the plant extract hand cream. The full score possible for each item was 5 points. It is important to clarify the details of the sensory evaluation criteria for this study. Odor was evaluated on a scale of 1 to 5, where 5 indicates a very pleasant odor and 0 indicates a very unpleasant odor irritation was evaluated on a scale of 1 to 5, where 5 indicates no irritation and 0 indicates very strong irritation moisturization was evaluated on a scale of 1 to 5, where 5 indicates that the skin remains moist after 0.5 h of product use and 0 indicates that after 0.5 h of product use, the skin had become dry freshness was evaluated on a scale of 1 to 5, where 5 indicates a fresh skin feeling and 0 indicates a greasy skin feeling and tightness was evaluated on a scale of 1 to 5, where 5 indicates no tightness and 0 indicates a strong tightness. The specific scoring for the sensory evaluation from the volunteers is shown in Table XII. The sensory evaluation data in Table XII indicates that this hand cream has the following product characteristics: a pleasant odor, no significant irritation, good moisturizing sensation, moderate oiliness, and no tightness. The skin moisture content test results (Table XIII) indicated that after using this hand cream, skin moisture content increased, but to varying degrees. After 1 and 2 weeks of use, Table IX Physical and Chemical Properties of the Plant Extract Hand Cream Serial number Viscosity (cp) pHa Experiment 1 10,306.11 7.44 Experiment 2 10,309.65 7.61 Experiment 3 10,305.90 7.54 Average 10,307.22 7.53 a Experiment temperature: 25.3°C, relative humidity: 46%. Table X Centrifugation Test Resultsa Sample number Before centrifugation After centrifugation pH Viscosity (cp) pH Viscosity (cp) 1 7.44 10,306.11 7.42 10,351.14 2 7.61 10,309.65 7.59 10,372.45 3 7.54 10,305.90 7.51 10,366.40 a Test temperature: 25°C, relative air humidity: 46%.

30 JOURNAL OF COSMETIC SCIENCE respectively, Volunteer A’s skin moisture content increased by 18.0% and 29.8%, Volunteer B by 19.7% and 29.9%, Volunteer C by 8.7% and 28.4%, and Volunteer D by 16.5% and 28.8%. Taken together, using the hand cream for 1 week led to an average skin moisture content increase of 15.7%, which further increased to 29.2% after 2 weeks of use. The results of the transdermal water loss test (Table XIII) indicated that using the plant extract hand cream reduced transdermal water loss. After using the hand cream, the transdermal water loss dropped by 10.2% and 31.5% for Volunteer A, 11.6% and 30.8% for Volunteer B, 16.0% and 23.6% for Volunteer C, and 21.1% and 27.7% for Volunteer D, Table XI Thermal Stability Test Resultsa Sample number Before thermal cycling After thermal cycling pH Viscosity (cp) pH Viscosity (cp) 1 7.44 10,306.11 7.47 10,297.68 2 7.61 10,309.65 7.57 10,301.56 3 7.54 10,305.90 7.48 10,302.40 a Test temperature: 25°C, relative air humidity: 46%. Table XII Sensory Evaluation Scores Volunteer number Odor Irritation Moisturization Freshness Tightness 1 4 4.5 5 4.5 4.5 2 4.5 4.5 5 4.5 5 3 4 4 4.5 4 4.5 4 3.5 3.5 4 3.5 4 5 4 4 4.5 4 4.5 6 3 3.5 4 3.5 3.5 7 4 5 5 4.5 5 8 3.5 4 4.5 3.5 4 9 3.5 3.5 4 3.5 4 10 4 4 4.5 4 4.5 11 3 3.5 4.5 3.5 4.5 12 4 4 4.5 4 4.5 13 3.5 3.5 4 3.5 4 14 3 3.5 4.5 3.5 4 15 4 4 4.5 4 4.5 16 3 3.5 4 3.5 4 17 3.5 3.5 4.5 3.5 3.5 18 4 4 5 4.5 4.5 19 3 3.5 4 3.5 3.5 20 4.5 5 5 4.5 5 21 3.5 4 4.5 4 4.5 22 4 4.5 5 4.5 4.5 23 3.5 3.5 4.5 3.5 4.5 24 4.5 5 5 4.5 5 25 3.5 3.5 4.5 3.5 3.5 26 4.5 5 5 4 4.5 27 4 4 5 4.5 4.5 28 3.5 3.5 4.5 4 4.5 29 3.5 4 5 4 4.5 30 4.5 4.5 5 4.5 4.5