336 JOURNAL OF COSMETIC SCIENCE pooing and dyeing on the luster of hair. Maeda et al. (6) have presented luster measure- ments performed by using a color image processor, which analyzed the pattern of light reflected by a natural-hair wig on a model head. The data were obtained by scanning across highlighted and dark areas of the obtained image, and could be presented in a plot similar to a goniophotometric scattering curve. The authors reported good agreement between calculated luster and the rating of luster obtained by visual inspection of hair tresses. Recently, hair luster was measured using diffuse reflectance spectrophotometry in which the color difference parameter, AE, was used as an indicator of luster (7). The method of subjective shine evaluation is also commonly used and can provide a useful guidance for formulators. The results can be in good agreement with instrumental methods provided the experimental setup assures uniform orientation of hair samples and reproducible (from sample to sample) illumination conditions. In this paper we discuss the experimental details of luster measurements by employing image analysis for quantifying the light distributions of hair illuminated with white, collimated light. The results for various types of untreated hair, as well as for dark brown hair modified with polymers and oils, are discussed. The interpretation of the data is based on the character (shape) of the light-scattering curves, calculated luster parameters, and visual examination of the digital images of hair. EXPERIMENTAL METHODS The entire luster evaluation apparatus was housed in a wooden box coated with black Formica and having the dimensions of 2 ft in width, 21/2 ft in depth, and 3 ft in height. As shown in Figure 1, hair tresses were mounted on an anodized aluminum cylinder, 31/2 inches in diameter. A collimated halogen light source was placed 7l/2 inches above the digital camera, providing an incident angle of approximately 30 ø relative to the optical axis. Linear polarizers were placed in front of the light source and the camera. This allowed us to view all reflected light (specular and diffuse) when the polarizers were parallel and diffuse reflection when they were perpendicular. The camera, the polarizer, and the mounting cylinder were attached to aluminum posts that were mounted to an anodized optical peg board, which provided the underlying support for the instrument. An Olympus Camedia El0 digital camera with a resolution of 4 megapixels was em- ployed as the image collection device for all studies presented in this report. Image analysis was carried out using Sigma Scan Pro 5.0 (SPSS) software, which enabled us to obtain the light intensity (luminance) distributions along a given hair tress. The method was previously described by Maeda et al. (6). Based on this procedure we are able to plot the data in Excel 2000 (Microsoft) in the form of a two-dimensional graph, providing luminance as a function of distance along the hair tress. The data were further analyzed by integrating the area under the luminance curves in order to obtain the values of the luster parameters. All luster data represent an average of the results obtained on at least three tresses except for Nickerson contrast gloss data, which were not analyzed statistically. On the other hand, the luster parameters for untreated hair represent an average of measurements obtained on 28 tresses.

LUSTER QUANTIFICATION OF HAIR 337 Linear Polarizers • Top of Hair Tress Cylinder, which hair is mounted to. Digital Camera Bottom of Hair Tress Figure 1. Scheme of an apparatus to measure the luster of hair. MATERIALS Luster analysis was performed on natural white, light blonde, light brown, medium brown, and dark brown hair purchased from IHI & Products, Inc. (Valhalla, NY). Hair samples were pre-cleaned with a 3% ALS solution and thoroughly rinsed prior to experimentation. Hair tresses were obtained by gluing 3 g of fibers to 1.5 x 1.5-inch plexiglass tabs with Duco cement. The length and width of each hair tress were 10 inches and 1.25 inches, respectively. Dark brown hair was treated with a variety of polymers and oils. Phenyl trimethicone (Si Tec TM PTM 200, ISP), amodimethicone (DC Q2-8220, Dow Corning), and castor oil (Hanson) were used as ethanolic solutions. Butyl ester of PVM/MA copolymer (Gantrez © ES-425), vinyl caprolactam/PVP/dimethylaminoethyl methacrylate copolymer (Advan- tage © LC-A), and isobutylene/ethylmaleimide/hydroxyethylmaleimide copolymer (Aquaflex © FX-64) were all ISP products and were also used in the form of ethanolic solutions. All polymer and oil solutions were applied to hair in the amount of 1 g at a concentration of 2% (w/w) using a disposable pipette. A product containing ZnO was formulated as a 1.5 % aqueous suspension stabilized with a combination of acrylates/beheneth-25 methacrylate copolymer (Aculyn © 28, ISP) and VP/acrylates/lauryl methacrylate copolymer (Styleze © 2000, ISP). A synthetic sebum formula containing the following ingredients was prepared as a 5 % (w/w) solution in hexane: 20% Olea europaea (olive) fruit oil (Lipovol O, Lipo Chemi- cals) 15% cetyl esters (synthetic spermaceti, Koster Keunen) 15% Cocos nucifera (coconut) oil (Lipovol C-76, Lipo Chemicals) 10% palmitic acid (Aldrich) 10% paraffin (paraffin wax fully refined, Frank B. Ross Company) 10% oleic acid (Emersol 6321, Cognis Corporation) 5 % stearic acid (Emersol 150, Cognis Corporation) 5 % squalene