LIGHT SCATTERING THEORY TO MEASURE RINSABILITY OF HAIR CONDITIONERS 401 this could be attributed to the material’s poor water solubility. It is also worth noting that Conditioner C had more conditioner material left on the hair compared with conditioners B (the di-Behenyl quat) and D (the non-ionic). Conditioner D, our non-ionic emulsifying negative control system, as expected, rinsed out very quickly, leaving very little product on the hair after 60 s. As it can be predicted, this system would not exhibit any substan- tivity to the bleached hair surface, and therefore would be expected to rinse out quickly with little to no residual product left behind. The data on the rinsability of the conditioners on virgin hair are displayed in Figure 3. Some similarities are observed in the rinsing profi le of some of the conditioner systems, namely Conditioners C and D on both bleached and virgin hair, as exhibited in Figures 2 and 3. Conditioner C, the amine salt, once again took the longest to rinse out of virgin hair before it plateaued, thereby exhibiting a similar profi le to its performance on bleached hair. However, on virgin hair, more residual conditioner C material was left on the hair when compared with the other systems. Conditioner D, our negative control, once again exhibited similar rinsing patterns as it did in its performance on bleached hair, by rinsing out the quickest and leaving very little to no residual material on the hair surface as would be expected. Conditioner A and B, the behenyl and di-behenyl quat system respec- tively, exhibited similar rinsing profi les on virgin hair, contrary to their performance on bleached hair. Both conditioner systems had less affi nity for or were less substantive to virgin hair, thereby both products rinsed out quickly, but with Conditioner A having much less residual product remaining on the hair as compared with its rinsing profi le on bleached hair. TIME CONSTANT RELATIVE TO RESIDUAL CONDITIONER MATERIALS To further describe the pattern in these rinsing curves, a mathematical representation of the percent time constant and percent residual material is illustrated in Figures 4 and 5, Figure 3. The Rinsing Behavior of Conditioner Systems on European Virgin Hair as a Function of Time.

JOURNAL OF COSMETIC SCIENCE 402 representing the rinsing behaviors of the tested conditioners seen previously for bleached hair and virgin hair in Figures 2 and 3, respectively. The time constants (%) were calcu- lated based on slope and time for each rinsing curve, indicated by the fi rst bar in Figures 4 and 5. Furthermore, percent residue of conditioner product left on the hair was also Figure 4 . Time constant of slopes of the curves as a function of remaining residual conditioner product left on European bleached hair. Figure 5. Time constant of slopes of the curves as a function of remaining residual conditioner product left on European virgin hair.