Hair Colouring by the Use of Dyestuffs Formed by Oxidation of (+)-Catechin Combined with Photosensitisers Absorbing Visible Light

Hair colouring by using dyestuffs formed by the oxidation of (+)-catechin (Cat.) under light irradiation was studied and the oxidation system was combined with photosensitisers which absorb visible light and generate oxidants. Rose bengal (RB) and Methylene Blue (MB) were used as the visible light photosensitiser. Hair was treated with the solutions containing them and was irradiated with artificial sunbeam in dry condition or in Cat. aqueous solution. It was found that hair is not coloured when it is pretreated with the aqueous solutions containing Cat., RB and MB, and irradiated with the light in the dry condition (dry system). In contrast, hair is coloured most when it is pretreated with the solutions containing RB and MB, and then irradiated with the light in Cat. aqueous solution (wet system). The RB and MB in hair may promote the oxidation of Cat. and production of colourants to give better colouration results, when the treated hair is irradiated with visible light in the solution condition.