NOVEL ACID-TYPE HAIR COLOR TECHNOLOGY Benzyl alcohol Ethyl alcohol Metal ion* A1Cl3 ·6H2O Acid** Glycolic acid Acid orange 7 Acid red 52 Hydroxyethyl cellulose Ager HCl Table I Formulation of Experimental Samples (w/w %) Sample A 8 20 (0.02 mol/1)*** (4 mmol/1)*** Sample B 8 20 (0.21 mol/1)*** 0.44 0.15 0.7 1.8 31 Sample Ct 8 20 0.5 1.6 0.44 0.15 0.7 1.8 Sodium lactate Ion-exchanged water pH adjusted to 3.0 Up to 100 pH adjusted to 2.3 pH adjusted to 3.5 Up to 100 Up to 100 "j" This formula is "permanent" acid-type hair color. *Metal ion: ZrC14, A1Cl3 ·6H2O, ZnC1 2 , FeC1·4H2O, CaC12·2H2O, MgCl2·6H2O, CuSO4·5H 2 O, FeSO4·7H2O, BaCl2 ·2H2O, MnCl2 ·4H2O, NaCl, or KCl. ** Acid: formic acid, glycolic acid, lactic acid, acetic acid, tertronic acid, or glycine hydrochloride. *** Final concentration. COLOR BRIGHTNESS AND COLOR LONGEVITY TEST Tresses (2 g) were treated with hair colorant (10 g) obtained as described above at 30 °C for 10 or 30 min. After the tresses were washed and dried, the colors were measured by a color analyzer (Color-Eye 7000, Sakata Inx, Tokyo). Color brightness was expressed as the degree of color changing (�E) before and after the treatment. This �E values are written as �Ed y ed hair• The Hunter Lab system was applied for calculating the �E values (12). The �E values, which express the strength of the color, are expressed by the following formulas: �E d yed = V (Ldyed - Lo) 2 + (a d y ed - ao) 2 + (bdyed - bo) 2 �£washed = V (Lwashed - Lo) 2 + (awash e d - ao) 2 + (bwash e d - bo) 2 (L d y ed : L value after dyeing. ad y e d : a value after dyeing. bd ye d : b value after dyeing. Lwashed: L value after washing. awash e d : a value after washing. bwashed: b value after washing. L0: L value of tress. a0: a value of tress. b0: b value of tress.) The tresses were then soaked in 2% SDS (100 ml), and shaken by a sample shaker (Uni Thermo Shaker NTS-3000, Eyela, Tokyo) at 30°C at 120 rpm for 10 min. The tresses were soaked by water and dried by a hairdryer. After this process was repeated six times, the colors of the tresses were measured again. This �E value is written as �Ewashed hair• SELECTION OF ACIDS The acids were investigated to obtain the best color-enhancing effect and color longevity. A concentration of 0.21 mol/1 acid (formic acid, glycolic acid, lactic acid, acetic acid, tertronic acid, or glycine hydrochloride) was added to the hair colorant of Sample B in Table I. The tresses (2 g) were treated with hair colorant (10 g), as described above, at

32. JOURNAL OF COSMETIC SCIENCE 30°C for 10 min. The color longevity effect was also tested as described above. The optimal concentration of gl ycolic acid was investigated at a specific pH of 3. 5. Color longevity was also tested as described above. The pH dependence of the color brightness of the hair colorant of Sample B in Table I, which contains 1.6% glycolic acid, was also investigated. The pH was adjusted to 2.3-4.1 with sodium lactate. The tresses (2 g) were treated with hair colorant (10 g) by the same method at 30 °C for 10 min. FORMATION OF DYE�METAL ION COMPLEX The formation of a dye-metal ion complex was observed by a microscope with a polar­ izing filter (BX50, Olympus, Tokyo). AlC1 3 ·6H2O (0.5 g) was dissolved in 100 ml of water. Acid orange 7 (0.1 g) was dissolved in 100 ml of the mixture of benzyl alcohol (8%) and water. The separated benzyl alcohol phase containing acid orange 7 was collected by a pasture pipette. One drop of the benzyl alcohol phase was put on a preparation, and one drop of the water phase was put next to the benzyl alcohol phase. The boundary face between benzyl alcohol phase and water phase was observed by the microscope with a polarizing filter. The condition for foaming dye-metal ion complex was studied in a simple-solution system that was prepared by dissolving acid orange 7 (0.5%), A1Cl 3 ·6H2O (0.5%), and benzyl alcohol (8%, 5%, 3%, 2%, 1 %, or 0%) in water. The separation of benzyl alcohol was also observed in a simple-solution system that was prepared by dissolving acid orange 7 (0.05%), A1Cl 3 ·6H2O (0.5%), benzyl alcohol (8%), and ethyl alcohol (20%, 15%, 10%, 5%, or 0%) into water. SELECTION OF MET AL ION A test sample was formulated of Sample A in Table I. Four mmol/1 of acid orange 7 and 0.02 mol/1 of metal ion (ZrC1 4 , A1Cl 3 ·6H2O, ZnC12 , FeCl2 ·4H2O, CaCl2 ·2H2O, MgCl2 ·6H2O, CuSO4 ·5H2O, FeSO4 ·7H2O, BaC12 ·2H2O, MnCl2 ·4H2O, NaCl or KCl) were added into the mixture of benzyl alcohol, ethyl alcohol, and water. The pH was adjusted to 3.0 using HCl. After being treated with the simple-solution system (50 ml) at room temperature for 20 min, the tress was rinsed with water and dried. The color of each sample tress was measured by a color analyzer (Color-Eye7000, Sakata Inx, Tokyo). The dyeing ability was expressed as the degree of color change (LiE) before and after the treatment (LiE d y ed ha ir- The dyed tresses were then soaked in 2% SDS water solution overnight. After washing and drying, the colors of the tresses were measured again (LiE washed haiJ The optimal concentration of AlC1 3 ·6H2O was investigated with the hair colorant described above. The tresses (2 g) were treated with the hair colorant (10 g) described above at 30 °C for 10 min. MICROSCOPIC OBSERVATION OF CROSS SECTION OF HUMAN HAIR The hair colorant of Sample C in Table I was obtained as described above. Tresses (2 g) were treated with the hair colorant (10 g) at 30 °C for 30 min. The dyed human hair