HAIR COLORING 51 3O 20 o 1 l0 • • 20 30 ?ime (rain) Figure 4. The effect of the treatment time in PPDA solution on coloring. 25% Hamamelis extract was used for pre-treatment. The treatments were carried out in 0.5% PPDA solution-suspended 0.2 g Ag-zeo- lite containing 10 wt% silver. Figure 6. It was not effective for coloring to use the high-concentration hamamelis solution above 10%. With this high concentration, the concentration of 1,3-buthylene glycol is consequently higher and it is thought to cover the hair surface and inhibit the diffusion of the dye molecules. OBSERVATION OF COLORED HAIR SURFACE The surface of colored hair was observed with SEM (Scanning Electron Microanalyzer X-650, Hitachi, Japan). The hair colored by Ag-zeolite and hamamelis extract was compared with that colored by hydrogen peroxide. While the coloring using hydrogen peroxide results in collapsed scales, that by silver-zeolite with hamamelis extract caused little apparent damage to the fiber surface (Figures 7a,b). SHAMPOO STABILITY The color stability to shampoo treatment is shown in Figure 8. There was little change in color in seven treatments. 40 • 0 : 25'C • • •: 37'C .- 20 •'•' ß • "" 0 0.5 1 .0 A9-Zeoloete Content (c//Smf) Figure 5. The effect of Ag-zeolhe content on coloring. 10• Hamamelis extract was used for pre-rrear- menr. The various amounts of Ag-zeolire containing 10 wt• silver were suspended in 8 ml of 0.1 • PPDA solution.

52 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 4O 2O , 210 I i 0 40 60 Hamamelis Extract Content (wt%) Figure 6. The effect of hamamelis extract content for pre-treatment on coloring. The hair tresses were immersed in the hamamelis extracts which were prepared in various concentrations. They were colored in 0.1% PPDA solution-suspended 0.2 g Ag-zeolite containing 10 wt% silver. ELUTION OF SILVER IONS IN SOLUTION FROM ZEOLITE The effect of pH between 7.5 and 11.0 on the silver ion elution from zeolite was investigated. The determination of silver concentration was measured after 30-sec incu- bation. It was shown that the higher the pH was, the more easily silver ions eluted (Figure 9). The zeolite skeleton destruction that was known to occur in strong alkali solution was not recognized under these conditions because the steep increase of silver ion concentration was not observed. The silver ion elution is considered to be caused by the ion exchange reaction with the cation of the appropriate size in the solution. To make sure of that, the relationship between eluting silver ion concentration and sodium concentration in the solvent was investigated. Sodium ion concentration was adjusted to 0-150 mM by dilution of the Carmody buffer with distilled water. The elution of silver ions increased according to increase of sodium ion concentration, as was expected (Figure 10). In order to increase the amount of the eluting silver ions for effective coloring, the relationship with Ag-zeolite content was investigated. The eluting behavior of silver ions was measured under conditions of various contents of Ag-zeolite from 0 to 1.0 g in 4 ml Carmody buffer. Below 0.1 g, the eluting silver ion concentration increased smoothly, but it decreased gradually above this (Figure 11). This is considered to be because the viscosity of the solution increased. It shows that there is an optimum con- tent of Ag-zeolite for effective coloring. RATE OF PPDA OXIDATION REACTION BY SILVER ION SOLUTION The time course of the absorption at 470 nm was measured. In Figure 12, the effect of the silver concentration on the reaction is shown. It shows that the increase of silver concentration slowed down the reaction rate and increased the amount of the final product. In the case of PPDA concentration, the reaction rate and the amount of products were proportional to it (Figure 13).