SENSITIVE PROBE OF HAIR SURFACE 231 SHAMPOO B1 SHAMPOO B1/ SHAMPOO C1 Figure 7. A dye-staining experiment testing the effects of washing with shampoos B1 and C1. The pink color of the swatch on the left indicates the presence of Polyquaternium-10 after washing with shampoo B 1. The absence of a pink color for the swatch on the right indicates the lack ofcationic binding sites as a result of complexation of Polyquaternium-10 from B 1 and myristate anion from C 1. order to obtain meaningful instrumental shine values, therefore, it is necessary to treat tresses, rather than single hairs, and to then measure the shine values for a number of hairs from each tress and average the results. Aside from the resultant quantitative data, there are two other advantages to treating tresses rather than single fibers. First, unlike the case with individual hairs, the shine of treated tresses can be subjectively assessed and, if desired, compared to instrumental data. In addition, the conditions employed in treating tresses are much closer to actual in-shower conditions than is true for single-fiber tests. In the latter case, even though a hair is exposed to only one to three drops of treatment solution, this is still more exposure than it would receive buried in a head of hair. Thus, although results from single-fiber tests are valid for the conditions employed, they would not necessarily be observed in normal usage. To confirm whether an observed effect on single hairs would actually occur under in-shower conditions, it is necessary to treat tresses (containing more than a thousand hairs) rather than single fibers.

232 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS In order to test the validity of equation 1, and also to confirm the preceding single-fiber results, a series of tresses was treated with shampoos B 1 and C1 along with four other commercial shampoos and SLS. Table I lists the detergents contained in the shampoos employed, along with any ingredients substantive to hair that they contain. Each of the tresses employed in the current experiments was washed at least five times with a particular shampoo in order to simulate buildup. Following this treatment, hair samples were taken from each tress for light-scattering measurements. Tresses were then mounted on the evaluation frame for assessment by panelists. A large series of shine evaluation panels was run to determine treatment differences among all seven of the shampoos employed. The results are tabulated in Table II, where the rankings are listed in order of decreasing shine. Those treatments connected with a vertical line are not significantly different from each other. Table II also lists the instrumental shine values measured for each treatment, along with the associated standard deviations. The numbers were obtained by calculating an average shine for each tress and then averaging the shine numbers for all tresses treated with the same shampoo. The agreement between the subjective rankings and the instrumental values in Table II was tested using the Spearman rank correlation coefficient method (13). The value calculated for the Spearman rank correlation coefficient was 1.00, which is significant at a level greater than 99%. The agreement between panelists' assessments and instru- mental measurements is thus excellent, and one can conclude, therefore, that the numbers calculated from equation 1 are a reliable measure of hair shine. The results in Table II also indicate that the single-fiber effects reported in the previous section can be expected to be observed under actual usage conditions. Tresses washed with shampoo B 1 were found to be duller than clean tresses, while tresses treated with shampoo B 1 followed by C 1 were found to be duller than those treated with B 1 alone. In general, the shampoo treatments in Table II were found to fall into three main groupings. In the first group, indicated by the first vertical line in Table II, none of the shampoos had ingredients highly substantive to hair. Treatments with these shampoos resulted in the shiniest hair observed, and we consider this hair to be essentially clean. The second group of shampoos in Table II all contained Polyquaternium-10 (a cationic polymer) or fatty acid salts (soap). These ingredients are substantive to hair and can Table I Shampoos Employed in Shine Experiments I Shampoo Primary detergent Substantive ingredients A1 Ammonium lauryl sulfate A2 Sodium laureth sulfate SLS Sodium lauryl sulfate B 1 Trideceth-7 carboxylic acid B2 Sodium laureth sulfate C! Sodium laureth sulfate C2 Sodium lauryl sulfate Polyquaternium- 10 Polyquaternium- 10 Sodium myristate Coconut acid (sodium salts) All shampoos except SLS and A2 were commercial products on sale in the United States. Shampoo A2 was product available in England.