SENSITIVE PROBE OF HAIR SURFACE 225 placed before the samples and photomultiplier tubes of the goniophotometer in all light-scattering experiments (2). The sample holder for the Brice-Phoenix photometer consisted of two supports, in- dented at the top and 4 cm apart, across which a single hair could be laid. A sample hair fiber was secured at one end and kept under constant tension by attaching a 2-gram alligator clip to the other end. Hair fibers had to be at least four inches long to conveniently fit on the sample holder. Because of the short distance between sample and photomultiplier tube in the Brice Phoenix photometer, samples run at an incident angle of 30 ø with respect to the perpendicular to the hair could only be scanned between 15 ø and 75 ø . This proved adequate for qualitative work, but for quantitative measurements, the incident angle was changed to 37.5 ø so that scans could be run between 7.5 ø and 75 ø . The scanning time for the latter interval was 72 seconds. For all experiments, hair fibers were oriented so that the direction of the incident light was toward the tip end of the hair (RER orientation in reference 1). The output from the goniophotometric measurements was sent to a Bascom-Turner 3120T electronic recorder (Bascom-Turner Instruments, Norwood, MA) that digitized each scan into 500 points. These points were then sent to an IBM PC computer for processing. SINGLE-FIBER SCREENING TESTS For single-fiber screening tests, single hair fibers were mounted on the goniophotometer sample holder and held taut with a 2-gram alligator clip. Treatments were then applied by dropping one or two drops of a test solution onto a glass microscope slide supported under the hair by a platform high enough so that the slide just missed touching the hair. After application of test solutions, the slides were moved back and forth under the hair for 60 seconds. Fibers were then rinsed with tap water in the same fashion. Following this, light-scattering curves were run, and the fiber was then either treated again or discarded. Note that some fibers are sufficiently irregular in cross section that movement of the sample holder from the instrument to the lab bench could cause the fiber to twist and change the light-scattering curve. A change in a measured curve was thus only consid- ered to be real if it could be reproduced after movement of the fiber holder. DYE-STAINING EXPERIMENTS Dye-staining experiments were performed using Sirius Red F3BA New, C. I. No. 35780. This is a high-molecular-weight (1372) anionic dye and was obtained from Mobay Chemical Co., Rock Hill, SC. Experiments were performed by wetting a 3-inch by 4.5-inch wool swatch (wool challis, Test Fabrics Inc., Middlesex, NJ) with water, applying 3 ml of a test shampoo, rubbing for one minute, and then rinsing under 100øF running tap water for one minute. Following this, swatches were either treated with dye solution or treated with 3 ml of a second shampoo, rinsed, and then treated with dye.

226 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Dye treatments consisted of placement of a swatch in 40 ml of a 0.5% solution of dye for 30 seconds. The swatches were then rinsed under 100øF running tap water for 30 seconds and hung up to dry. MEASUREMENT OF SHINE Shine, or luster, is perceived when an object scatters much more light at a particular angle or in a particular direction than in other directions. Under these conditions, surface highlights or brightness contrasts appear and the object is seen to be shiny (see, for example, references 6-8). In order to measure shine, therefore, one needs to be able to measure scattered light intensity as a function of angle. This is accomplished with a goniophotometer. Figure 3 shows, in rudimentary fashion, the operation of such an instrument with a hair fiber sample. In this case, the fiber is assumed to be held taut and is irradiated with light at an incident angle, i, that is prechosen and is measured with respect to the perpendicular to the fiber. The intensity of that portion of the incident light that is scattered by the hair is measured by rotating a photomultiplier tube, or light detector, from 0 ø to 75 ø. The illustration shows two of the positions of the photomultiplier tube. Typical results from a goniophotometer measurement are shown in Figure 2 for an undamaged Oriental hair. The light-scattering scan is presented as a plot of scattered light intensity as a function of angle. Figure 3. Rudimentary diagram of a goniophotometer experiment. A hair fiber is held taut and struck by incident light at angle i. Scattered light is then detected by rotatin'g a photomultiplier tube from 0 to 90 degrees with respect to the perpendicular to the fiber. Two of the photomultiplier positions are shown.