34 JOURNAL OF COSMETIC SCIENCE ment was CD 3 OD at 30°C. AL-Dye (10 mg) was dissolved in CD 3 OD (1 ml) and the supernatant was collected (Al-Dye/CD 3 OD). After the NMR spectrum of Al-Dye/ CD 3 OD was obtained, a few drops of 0.1 % EDTA in CD 3 OD was added to the NMR sample. The mixed solution was called Al-Dye-EDTA/CD 3 OD. SENSORY EVALUATION The obtained novel acid hair color was evaluated by 34 panelists (females, ages 21-57 years). Ten panelists were regular users of a conventional acid-type hair color for gray coverage (Test 1), seven panelists were regular users of a conventional oxidative hair color for gray coverage (Test 2), and 1 7 panelists were regular users of a conventional oxidative hair color for fashion shade (Test 3). The panelists compared a novel acid-type hair color with a conventional hair color that they regularly used. The evaluation result of the novel acid-type hair color was obtained by interviewing the panelists. To test various colors, the dye formulation of the novel acid-type hair color of Sample C in Table I was changed. The most popular brown shade on the market was used for Test 1 and Test 2, and the most popular orange, yellow, and ash (blue black) shades on the market for Test 3. RESULTS SELECTION OF ACIDS Added to the hair colorant of Sample Bin Table I was 1.6% of formic acid, glycolic acid, lactic acid, acetic acid, tertronic acid, or glycine hydrochloride. The color brightness and color longevity of the additional acid were investigated (Table III). In these acids, glycolic acid was chosen as the most preferable acid that can provide color brightness and color longevity effects because formic acid is undesirable in terms of its smell and safety. Formic acid Glycolic acid Lactic acid Acetic acid Glycine hydrochloride Tretronic acid Table III Characteristics of Acids Color brightness effect 55.808 55.863 54.942 53.813 54.53 53.783 Error range (mean +/- S.D.) 55.275-56.340 55.239-56.486 54.634-55.250 53.479-54.148 54.294-54.767 53.522-54.043 Color longevity effect(%) 90.519 96.562 94.816 95.111 94.011 93.593 Error range (mean +/- S.D.) 90.166-90.871 95.658-97.467 94.109-95.523 94.298-95 .923 93.329-94.693 93.081-94.104 The color brightness effect is expressed by 8-Elycl ha ir• The color longevity effect is represented by the following formula: Color longevity effect = 8-Ewashed ha j 8-Edyed ha ir x 100 where 8-Edyed hair and 8-Ewashed ha ir are the degree of color change after dyeing and washing. The error range was calculated by using the mean value and the standard deviation (S.D.). The Hunter Lab system was applied for calculating the 8-E values. The 8-E values, which express the strength of the color, is expressed by the following formulas: 8-Edyed = ✓ (Ldyed - La) 2 + (a dyed - ao) 2 + (b dyed - bo) 2 8-Ewashed = ✓ (Lwa.rhed - Lo) 2 + (awashed - ao) 2 + (bwashed - bo) 2 Ldyed : L value after dyeing. adyed : a value after dyeing. bdyed : b value after dyeing. Lwashed : L value after washing. awashed -' a value after washing. bwashed : b value after washing. L0: L value of tress. a0: a value of tress. b0: b value of tress.

NOVEL ACID-TYPE HAIR COLOR TECHNOLOGY 35 Then, the optimal concentration of glycolic acid was investigated to provide color brightness and color longevity effects. Concentration ranges from 0% to 3.2% of glycolic acid were investigated, and the color brightness and longevity effects were optimal at 1.6%. If the glycolic acid concentration increased, no additional benefit was expected (Table IV). Table V shows the pH dependence of the hair colorant containing 1.6% glycolic acid. Using glycolic acid is one of the key technologies of this study. SYSTEM OF NOVEL HAIR COLOR Figure 1 shows the observation of the boundary face between the benzyl alcohol phase and the water phase. The benzyl alcohol phase contains acid orange 7, and the water phase contains A1Cl 3 ·6H 2 O. When the benzyl alcohol phase and the water phase con­ tact, there is a concentration gradient of benzyl alcohol and water in the boundary phase. The dissolved A1Cl 3 ·6H 2 O diffused to benzyl alcohol phase and formed a complex with acid orange 7 at a certain concentration of benzyl alcohol. As a result, in the area near the boundary face between the water phase and benzyl alcohol phase in the benzyl alcohol phase, formation of a deposit considered to be the dye-metal ion complex was observed. It is indicated that the novel hair color penetrates into the hair and deposits the dye-metal ion complex in the hair. The condition that was unable to form the A1Cl 3 ·6H2O complex in the system was investigated. It is shown in Figure 2 that A1Cl 3 ·6H2O and acid orange 7 formed a precipitation that seems to be complex that is found under the condition of benzyl alcohol less than 2%. If benzyl alcohol is at a concentration of 3% or more, A1Cl 3 ·6H2O and acid orange 7 were unable to form a complex. This result inspired the possibility of a novel acid-type hair color that can be soluble in the bottle but forms a complex in the hair with benzyl alcohol at 2% or less. Figure 3 shows that the benzyl alcohol phase was dissolved evenly in the system under the presence of ethyl alcohol at more than 20%. SELECTION OF METAL IONS The color longevity effect of AlC1 3 · 6H2O, ZnCl2 , FeCl2 ·4H2O, CaC12 · 2H2O, MgCl 2 ·6H 2 O, CuSO 4 ·5H2O, FeSO4·7H2O, BaCl2 ·2H2O, MnCl2 ·4H2O, NaCl or KCl Table IV Optimal Concentration of Glycolic Acid Concentration of glycolic Color brightness Error range Color longevity Error range acid (%) effect (mean +/- S.D.) effect(%) (mean +/- S.D.) 0 42.86 42.84--42.88 69.84 69.48-70.2 0.4 44.54 43.49--45.59 77.13 76.49-77.77 0.8 45.76 45 .65--45 .87 82.2 81.94-82.46 1.6 47.76 47 .57--48.5 3 86.77 86.41-87.13 3.2 47.86 47.41--49.33 86.57 86.01-87.15 The color brightness effect is expressed by 8-Edy"d ha ir• The color longevity effect is represented by the following formula: Color longevity effect = 8.Edyed ha ir / 8.Ewashed ha ir x 100 where 8.Edyed hair and 8.Ewashed hair are the degree of color change after dyeing and washing. The error range was calculated by using the mean value and the standard deviation (S.D.).