Effects of Semi-Permanent Hair Dyes and Conditioning Polymers on the Color Enhancing Properties of Shampoo Formulations

This study examined the effectiveness of shampoos containing polymers and semi-permanent dyes in retaining the color of hair pre-dyed with permanent red oxidative dye. It concluded that polymeric conditioning agents in shampoos helped maintain color, while adding a cationic dye at a pH above the hair's isoelectric point resulted in a weak direct-dyeing effect. This effect was attributed to the deposition of colorants on the hair surface due to the short contact time. The combination of polymers and dyes enhanced color vibrancy and evenness, suggesting a beneficial interaction that provided consistent hair surface coverage.