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.).

36 pH 2.30 3.00 3.50 3.80 4.10 JOURNAL OF COSMETIC SCIENCE Table V Rerationship Between pH and Color Brightness Effect LlEc.lyec.l hair 51.54 47.86 46.55 44.09 42.97 Error range (mean +/- S.D.) 50.94-52.16 47.80--47.91 46.08--47.02 43.44--44.74 42.25--43.69 Tresses were dyed by acid-type hair colors, which contained 1.6% glycolic acid, for 10 min. The pH levels were adjusted by sodium lactate. LlEd yed hair is the degree of color change before and after dyeing. The error range was caliculated by using the mean value and the standard deviation (S.D.). Dye-metal ion complex Figure 1. Microscopic photographs by polarizing microscope. The benzyl alcohol phase contains acid orange 7, and the water phase contains A1Cl3 ·6H20. When the benzyl alcohol phase and the water phase contact, there is a concentration gradient of benzyl alcohol and water in the boundary phase. The dissolved A1Cl5 ·6H 2 0 diffuses to the benzyl alcohol phase and forms a complex with acid orange 7 at a certain concentration of benzyl alcohol. In the area close to the boundary face between the water phase and the benzyl alcohol phase in the benzyl alcohol phase, formation of the deposit considered to be the dye-metal ion complex was observed. is shown in Table VI. The longevity is represented by the LiE value ratio immediately after dyeing and washing. Table VI indicates that A1Cl 3 ·6H 2 O is substantially superior to the other metal ions in producing color longevity. ZrC14 formed precipitation, and no experiment was done. The results indicate that a specific metal ion provides color longevity under the specific pH. It is suggested that the color longevity effect depends on the strength of the bond between acid dyes and metal ions under the specific pH. To determine the optimal concentration of AlC13 ·6H2O, various concentrations of the ion were investigated. Figure 4 shows that 0.5% of A1Cl 3 ·6H2O was the optimal concentration to obtain color brightness. Using AlC1 3 ·6H2O in this hair color formula is one of the key technologies of this study. PERFORMANCE OF "PERMANENT" ACID-TYPE HAIR COLOR (FIGURE 5) Based on the results described above, the formula of Sample C in Table I was selected