476 JOURNAL OF COSMETIC SCIENCE Many researchers have measured the luster of hair fibers or tresses using a classical gloss meter, shine box, goniophotometer, laser-based multiple-angle goniophotometer, or image analysis (1-7). However, it is not an easy task to quantitate luster in hair tresses because of the necessity to align the fibers of the tresses consistently, to control lighting, to use multiple observers to evaluate the tresses, and to use replication (8). Hair care formulators have difficulty in obtaining meaningful shine values because of the discon­ tinuous nature of hair, which causes tremendous variations in hair tresses (5 ,8,9). Recently, a fast polarimetric video camera with high polarization contrast was intro­ duced to effectively separate specular and diffuse light, and to carry out accurate gloss measurements (9). Using polarized illumination, the polarimetric camera, called SAMBA, provides reliable hair luster information with a simple measurement. In ad­ dition, the application of atomic force microscopy (AFM) to study hair was recently introduced (10-12). This technology has made it possible to make extremely small measurements on hair fibers and to image the hair fiber surface using methods such as scanning electron microscopy. In this study, the effect of phenyl trimethicone on hair tress luster was quantitatively measured by employing SAMBA as the polarimetric imaging system. We used AFM to measure roughness following treatment with phenyl trimethicone. We evaluated the correlation between the instrumental data from SAMBA and consumers' perception of luster after phenyl trimethicone treatment. MATERIALS AND METHODS HAIR TRESS PREP ARA TI ON All measurements were made on dark brown oriental hair tresses (DeMeo Brothers, New York) at ambient conditions (22° ± 1 ° C and SO ± 5% relative humidity). The hair samples were about eight inches in length and approximately 2 grams in weight. Tresses were washed twice with a solution of ammonium lauryl sulfate (4.5% w/w) in deionized water. They were rinsed under warm (40°C) running water for 30 seconds between washings and for 60 seconds after the second washing. Excess water was squeezed from the tresses by pulling them between two fingers. The tresses were laid on a clean paper towel and allowed to air dry overnight at ambient conditions (22° ± 1 ° C and SO ± 5% relative humidity). HAIR LUSTER MEASUREMENT The hair luster evaluation apparatus used in this study was described previously (9). A polarimetric imaging system called SAMBA (Bossa Nova Technologies, Venice, Cali­ fornia) consists of a black-and-white polarization camera (760 x 580 resolution) to record line profiles, polarized linear neon illumination, a hair cylinder, and SAMBA 12-bit hair-luster software. Figure 1 shows some geometric details of the system. SAMBA is based on the analysis of the light scattered by a hair tress and its decompo­ sition into specular light, surface-scattered light, and volume-scattered light or diffused light. The SAMBA camera takes linear polarization images in real time using a fast

EVALUATION OF LUSTER IN HAIR 477 (1) Figure 1. Photograph (A) and diagram (B) of SAMBA system. The distance between camera lens and sample is eight inches (De), and the sample is illuminated at a 12 ° angle (a) at seven inches distance (Di). (1) Polarization camera, (2) polarized illumination, (3) sample cylinder, (4) hair tress. liquid crystal, which allows switching rapidly between the parallel polarization image and the cross polarization image. The camera takes ten images of a sample, processes each image, and averages all results. In order to proceed to the analysis of the light scattered by the sample, the sample is illuminated with a polarized light source using a uniform linear neon illumination. The illumination is composed of two neon tubes (6 W per tube) and a polarizing filter. The hair tress holder is cylindrical the diameter of the cylinder is four inches, and it is black in color to minimize the light reflection on it (Figure lB.). The software provides calibration, acquisition of polarization images, and luster measurement, and analyzes the shine band by packets or groups of vertical lines. The width and length of a hair tress (2.0 grams) to be measured were one inch and eight inches, respectively. Usually, hair tresses are tied in a bunch at the root end and free at the distal end. The hair tress was fastened on the hair cylinder with two tappets at the two ends of the cylinders. The hair tresses were loaded on the hair cylinder to keep them aligned during the evaluation, and the hair tresses were uniformly aligned in the same direction with a comb to ensure reliable results. Hair luster was measured with SAMBA in a dark box before treatment. Luster (L) was calculated by the equation of Reich and Robbins (5 ): s L=---- D X W112 where S = parallel polarization - crossed polarization, D W 112 = the width of the specular peak at half-height. crossed polarization, and The specular and diffuse data were analyzed by integrating the area using SAMBA 12-bit hair-luster software. Phenyl trimethicone (Dow Corning, USA) was dissolved in absolute ethanol (Merck, Darmstadt, Germany) at different concentrations. Absolute ethanol was also used as a base. Phenyl trimethicone (200 µl) was dropped onto the