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.

266 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The above radiolabeled compounds were diluted in their non-radioactive counterparts so that the final activities were between 0.1 and 0.3 microcuries per gram of solution. Wool swatches (7.6 x 11.4 cm wool challis, Test Fabrics, Inc., Middlesex, NJ) were prepared for radiotracer experiments by overnight immersion in a 1:1 mixture of acetone and ethanol. Following overnight drying, the cleaned swatches were cut with pinking shears into 0.14-g segments having areas of approximately 8.4 cm 2. At least five of the cut segments were prepared for each treatment under study. In all experiments, cut swatches were wetted with tap water, excess water squeezed out, and the swatch laid on a stainless steel wire gauze placed over a beaker. Following this, either 0.3 or 0.15 ml of a test material was applied to the swatch as evenly as possible. The wool was then rubbed for one minute between two lengths of rubber tubing mounted on stainless steel rollers especially constructed in our laboratories. After rubbing, swatches were rinsed in a beaker of tap water for 45 seconds, followed by a 15-second rinse in a second beaker. After the latter rinse, very little radioactive material could be removed from the swatches and a final rinse was performed for one minute under 100 ø F running tap water. Depending upon the particular experiment, after the above treatment, wool swatches were either hung up to dry overnight or treated again after excess water was squeezed out using rubber tubing placed over the ends of crucible tongs. Following treatment and drying, wool swatches were dissolved by placing each in a glass counting vial, adding 1 ml of 2M NaOH, and heating in an oven at 80 ø C for 1.5 hours. Three reference vials were also prepared in which a wool swatch was dissolved following addition of a known amount of radioactive material. After cooling, approximately 12 ml of Aquasol-2 LSC cocktail was added to each vial, followed by addition of 0.25 ml of concentrated perchloric acid. The vials were then shaken vigorously, resulting in a clear solution ready for counting. All measurements with radiotracers were run using only one radiolabeled substance at a time. Thus, for example, in experiments in which both conditioner and detergent deposition were measured for a given treatment series, the series was run twice, once with radiolabeled detergent and once with radiolabeled conditioner. LIGHT-SCATTERING MEASUREMENTS The use of a goniophotometer to carry out light-scattering measurements was described in reference 1. In the current work, all goniophotometric measurements were performed using a Murakami GP-1R automatic goniophotometer purchased from Hunter Associ- ates Laboratory, Reston, VA. The GP-1R, which employs collimated light from a tungsten halogen lamp, has several advantages over the Brice-Phoenix photometer employed in the previous work (1). Among these are the fact that it is a double goniometer instrument so that the sample can be turned to any angle desired with respect to the incident light. In addition, it has a large sample compartment permitting the sensitive stepping motors to run scans from 0 ø to 75 ø (or a full 360 ø if so desired). Finally, the instrument accuracy is quite high, with a specified scan repeatability of ---0.2%, an angle accuracy of ---20', and a pho- tometric accuracy of ---0.5 %.