Effects of co-surfactant and conditioning agent on colour

Optimising the cleansing efficacy of shampoos in relation to colour protection claims is of interest to formulators. This study investigates the effects of two co-surfactants and a range of conditioning additives, polycationic and silicone-based, on the colourfading of hair tresses treated with red oxidative hair dye and put through repeated wash-and-dry cycles. The results indicate that the choice of co-surfactant alone, and in combination with the conditioning additives, can significantly influence the colour fading of red oxidative dye treated hair during shampooing. The amphoteric co-surfactant offered statistically significant improved colour retention, compared to the nonionic. Furthermore, the silicone based conditioning additive delivered enhanced colour retention in comparison with the selected cationic polymers. 

Present in the hair cortex is melanin, which gives hair its natural colour. Modern consumers often use colorants with variable degree of longevity in order to change or enhance their natural hair colour. The permanent hair dyes, also referred to as oxidative dyes, have two components which are mixed just before application. The alkalising agent, hydrogen peroxide, swells the hair, enabling the dye precursors and a catalysing agent to reach the cortex. These promptly undergo several steps of chain reactions, producing new chromophores which are too large to diffuse out of the hair fibre.¹ Despite that, it is observed that hair treated with red hair dyes is particularly prone to fading after UV exposure and shampooing. Studies have quantified the precise degree of colour loss using spectrophotometric measurements based on the CIELAB (Commission Internationale de l’Eclairage’ or ‘International Commission on Illumination’ [eng.]) system. For example, Medice and Joekes² found that red coloured hair tresses lost colour to a larger extent than those dyed using black, brown and blond hair dyes, while Fernandez et al³ measured total hair colour loss of bleached and coloured hair as DE=2.97. Zhou et al4 recorded DE>4 for dyed hair tresses soaked in surfactant solutions, also noting time and pH dependant curves. Thus colour fastness of the hair dyes is not only a key performance characteristic of the dye formulation, but could be also of high importance when formulating targeted wash products. 

Primary surfactants are most commonly anionic, due to the superior cleansing and foaming performance of these materials. Kiplinger et al⁵ studied the effects of sulfates (SLS and SLES) on colour changes, concluding that their substitution by milder anionics, or the addition of amphoteric cosurfactants, can reduce the rate of colour fading during shampooing.