During the daily care as cleansing, bleaching, ironing and others the hair fiber becomes damaged due to alterations in superficial charges, cuticle breakage and the protein loss from cuticle and cortex (1,2). Cationic formulations are used to treat damaged hair fiber. Cuticle and cortex properties change by the adsorption and diffusion of formulation ingredients (1,2). The adsorption of cationic surfactants containing quaternary ammonium on hair surface has been majority attributed to electrostatic interactions between the negatively charged cuticle after shampooing and the positive charge of these compounds (1). The uniformity of the adsorbed layer has direct influence on damaged hair texture (3,4). Recent advances in computational image analyses and very low angle illumination on light microscope allow us to develop a new approach of hair texture evaluation (5). On the other hand, the diffusion of ingredients into cortex has been attributed mainly to size, concentration and affinity between the molecule and hair. Cationic surfactants play an important role in the diffusion process due to the deposition and charge-charge interactions on hair surface (1).
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