224 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Following mounting, tresses were evaluated by sixteen to twenty panelists, each of whom was asked to rank the tresses in order of relative shine. After evaluation, tress positions were interchanged and a new set of evaluations performed. This was done in order to minimize any positional biases. The data from the above rankings were evaluated statistically by the Friedman test (5). This is a non-parametric test and has several advantages over the corresponding para- metric methods since it does not require a normal distribution and makes no assump- tions concerning variance of the data. GONIOPHOTOMETRIC MEASUREMENTS The bulk of the goniophotometric measurements were performed using a Brice-Phoenix light-scattering photometer (Virtis Co., Gardiner, NY), modified by attaching a re- corder motor to the graduated disc in order to automate scanning of receiving angles. Subsequent to the research described in this paper, a Murakami GP-1R automatic goniophotomer was purchased (Hunter Associates Laboratory, Inc., Reston, VA). This instrument is not subject to the scanning limitations experienced with the Brice- Phoenix photometer. The sample light-scattering curve presented in Figure 2 was produced with the GP-1R photometer. In order to maximize the accuracy of the diffuse scattering measurement (D in Figure 2), polarizers having directions of polarization perpendicular to the plane of incidence were 0 15 30 45 60 75 SCATTERING ANGLE Figure 2. A typical light-scattering curve for a virgin Oriental hair. D is the diffuse reflectance and is calculated by measuring the area under the straight line connecting the light intensities at 0 and 75 degrees. S is the specular reflectance, and is the total area under the curve minus the diffuse region. W is the width of the curve at half height.

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.