264 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS formation was investigated for a large number of detergents, the relative efficacy of most of these detergents in cleaning conditioner soil was not established. In this paper, it is shown that the light-scattering techniques described in reference 1 can be used to rapidly and conveniently answer the above questions concerning condi- tioner/detergent interactions on hair. As in reference 1 for shampoo complexes, it is shown, using light scattering, that conditioner:detergent complexes formed on the hair are very dulling and difficult to remove with common detergents. These effects are shown to be readily measured on single fibers, on hair tresses, and even on full heads of hair. Following this, surfactants not exhibiting formation of insoluble complexes on hair are presented, and the relative conditioner cleaning efficiencies of a large number of sur- factants is determined. The above measurements are performed with both conditioner actives and fully formu- lated conditioners. The results from both types of experiment are confirmed and sup- plemented with more detailed radiotracer experiments than were run in the previous work. The results in this paper show that light scattering can be used to rapidly and quanti- tatively measure the practical effects on hair of many hair care products. As was stated previously (1), much of this type of information would be difficult or impossible to obtain using other techniques. EXPERIMENTAL TRESS PREPARATION All tresses were prepared with three grams each of human hair purchased from DeMeo Brothers, New York. In order to minimize scattering from the interior of the hair, only virgin, Oriental hair was used (1). Permed tresses were prepared by perming 60-gram bundles of hair with a standard commercial perming product. After the initial perm, the hair was washed twice with a 20% solution of SODS, a detergent consisting of 45 % sodium octeth- 1 sulfate and 55 % sodium deceth-1 sulfate (Vista Chemical Co., Austin, TX). Following this treatment, the hair was permed and washed again, and then divided into three-gram tresses. TRESS TREATMENTS For all comparison series, a minimum of three tresses was prepared for each treatment. In addition, three control tresses, treated only with 20% SODS and representing "clean hair," were prepared for each series. When carrying out a comparison experiment, succeeding tresses in a series received different treatments so that any particular treat- ment was staggered throughout the entire series. For stearalkonium chloride (SAC)/detergent experiments, tresses were subjected to two prewashes, followed by three treatment cycles. In commercial conditioner/detergent experiments, the number of treatments was increased to five.

SURFACTANT INTERACTIONS 265 Prewashes were performed by applying 5 ml of 20% SODS to a tress, rubbing by hand for one minute, and then rinsing for one minute under running tap water at a temper- ature of 100 ø F. Treatment cycles for SAC/detergent experiments consisted of treatment with 2 ml of 1% SAC in a 30:70 ethanol/water mixture, rinsing, treatment with 0.5 ml of a 20% solution of a test detergent, and then another rinse. Each treatment solution was rubbed into the tress for one minute, while each rinse was carried out under 100 ø F running tap water for one minute. Commercial conditioner/detergent experiments were run in the same fashion as above, except that treatment quantities were increased to 5 ml of conditioner and 2 ml of detergent. HALF-HEAD TESTS Half-head tests were carried out by parting a panelist's hair down the middle and subjecting each half to different treatments. All treatment samples in each test were rubbed into the hair for one minute, while the duration of all rinses was also one minute. All half-head tests were begun by washing each side of the head with 5 ml of the test shampoo (detergent) to be used on that side. This was performed twice, followed by a rinse each time. Following the above, both sides of the head were treated with either 15 g of 6% SAC in a 30:70 ethanol/water mixture or 15 g of a commercial conditioner. This treatment was followed by a water rinse, after which each side of the head was treated with 5 ml of either 20% SODS or 20% triethanolamine lauryl sulfate (TEALS) and then rinsed again. The entire conditioner/surfactant cycle was repeated three times. For SAC experiments, 30-40 hairs were taken from each side of the head after the last shampoo and put aside for light-scattering measurements. The hair was then blow- dried, combed as straight as possible to avoid orientation artifacts, and evaluated sub- jectively. All subjective evaluations were carried out in a darkened room under an overhead point source lamp (Smith-Vicker fffi710 lamp Sylvania FBD, 500-watt bulb) by four to six trained evaluators. Note that, of the evaluators, only the hairdresser knew which treat- ment each side had received. For commercial conditioner experiments, the procedure followed was the same as the above, except that, in most cases, sampling and subjective evaluation were carried out after both the last conditioner and the last detergent treatments. RADIOTRACER EXPERIMENTS [14C]SAC, [14C]CTAC, [35S]ammonium lauryl sulfate (ALS), [35Sisodium deceth-2 sulfate (SDES-2), and [35Sisodium deceth-3 sulfate (SDES-3) were all synthesized in the radiotracer laboratories at Colgate. The precursor alcohols for the last two surfactants in the preceding list were provided by Vista Chemical Co., Austin, TX.