222 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS to exhibit excellent correlation with a formula developed to calculate hair shine using goniophotometric measurements. In addition to providing a quantitative measure of shine, the light-scattering methods developed in this work are shown to provide a means of following changes to the hair surface, including deposition (soiling and buildup), removal of particles (cleaning), and even interactions at the fiber surface. Single-fiber techniques are presented and shown to provide a rapid, qualitative means of determining the effects on hair fibers of various treatments. The results of shine mea- surements of tresses exposed to various treatments of interest are then shown to confirm and make quantitative the foregoing single-fiber results. Finally, the shine of hair tresses treated with various shampoos is measured and shown to be a function of the nature of the substantive ingredients found in particular sham- poos. The results in this paper show that light scattering can be used not only to obtain quantitative information about shine but that it can also serve as a sensitive probe of the hair surface, providing information difficult or impossible to obtain using other surface techniques. EXPERIMENTAL SHAMPOO EXPERIMENTS All tresses for shampoo experiments were prepared using three grams of human hair purchased from DeMeo Brothers, New York. In order to minimize scattering from the rear cuticle, only dark brown Oriental hair was used (1). For each comparison series, a minimum of three tresses was prepared for each shampoo treatment. In addition, three control tresses, treated only with 20% sodium lauryl sulfate (SLS) and representing "clean hair," were prepared for each series. In comparison experiments, succeeding tresses in a series received different treatments so that any particular treatment was staggered throughout the entire series. All tresses were subjected to five pretreatment washes with SLS, followed by five treatments with a test shampoo. In those cases where shampoo combinations were employed, five treatments with the first shampoo were followed by three treatments with a second. Pretreatment cycles were performed by immersing tresses for five minutes in 250 ml of 5 % SLS in a graduated cylinder. The tresses were then removed, rubbed by hand for two minutes, and then rinsed twice for one minute each in graduated cylinders containing 500 ml of deionized water. Treatment cycles were performed in the same manner as the above, except that a 2: ! tap water, shampoo solution was substituted for SLS, while tap water rather than deionized water was employed in rinses. Note that the tap water used in these experiments had a water hardness level of 80 ppm. SUBJECTIVE SHINE EVALUATIONS Subjective evaluation of tress shine was performed on groups of six tresses each, with

SENSITIVE PROBE OF HAIR SURFACE 223 three tresses mounted for each treatment. Figure 1 shows a photograph of the frame used for mounting tresses for subjective comparisons. Each tress is clamped at the root end, stretched over the cylinder, and secured at the tip. This setup insures that all tresses are oriented in the same manner toward the viewing light and also minimizes orientation differences among the individual hairs comprising the tresses. Tresses were viewed under two lamps, each of which contained two cylindrical, 60-watt tungsten bulbs. The lamps were placed side by side so that all four bulbs were in a single row approximately ten inches above the tresses. This configuration maximizes the chances that each tress receives the same amount of light. Figure 1. Photograph of frame used for subjective shine assessments. Tresses are clamped at the root end and stretched over the cylinder. A wooden block is then placed over the tip end and held secure by wedging a small piece of flexible tubing between the frame and the block.