Abstract
The staining mechanism of oxidation hair color on white hair and black hair in the same person was studied. The quantitative analysis using ICP MS showed that the content of metals in the white hair was much less than that of the black one. This was due to low level of melanin granules in the white hair, one of the predominant structures containing metals, that was observed with TEM and EDS-TEM. The results of this study also showed that the penetrating speed of oxidation dyestuff monomers and of direct dyes into both the black hair and the white hair was the same under the condition without hydrogen peroxide, and the speed of direct dyes under the condition with or without hydrogen peroxide was also the same, and using oxidative dyestuffs the black hair had much higher staining efficacy in the presence of hydrogen peroxide than white hair. The fact that transition metals catalyze the oxidation reaction of hydrogen peroxide has been known. Therefore, the difference in staining efficacy of oxidative dyestuffs in white hair and black hair in the presence of hydrogen peroxide in the staining solutions might be due to the difference of metal content that results from the difference in the number of melanin granules in the hair.
