MEASUREMENT OF HAIR LUSTER 291 METHODS Experimental optimization. In order to evaluate the instrument sensibility and to get the better instrumental conditions for human hair samples, several equipments were performed as described. Influence of position, viewing angle, and viewing aperture of the sample. This experiment was done by varying the position of a dark-brown tress (D-B) in the instrument, the viewing angle (2 ø and 10ø), and the sample-viewing aperture (5 x 10 mm and 20 x 10 mm). The sample-viewing aperture readings were taken in two different ways: first, by changing the hair tress position, and second, by retaining the hair tress position in the instrument sample holder. Influence of sample color, texture, and geometry. Diffuse-reflectance measurements were per- formed using a smooth plate with drops of "nanquim" black dye, a cylindrical capillary tube filled with "nanquim" black dye, a black hair tress (B) treated or not treated with brilliantine (cylindrical surfaces), and a smooth and a wrinkled surface of green paper. Current and adapted holder. Figure 1 shows the design of the adapted holder, which allows a better arrangement of the hair fibers, avoiding hair entanglement that could cause an increase in error. The less damaged dark-brown hair tresses (D-B1, D-B2, and D-B3 cleaned with ethyl ether for 8 h) were used in this experiment. Measurements were done first with tresses using the current holder. After that, the instrument was calibrated with the adapted hair holder and the measurements were repeated with the same tresses. Color parameter evaluation. This experiment was performed with 25-cm tresses of less damaged dark-brown hair (D-B), in order to verify the measurement reproducibility after treatments. The tress was divided into three samples (D-B1, D-B2, and D-B3), and the treatments were done in triplicate. The clean hair tresses were rinsed with 1 ml of the product for 2 min, immediately rinsed with distilled water at 35ø-40øC for 1 min, and dried with a hair drier for 1 min. DE* and DE values were obtained between the reference hair tress (zero difference, cleaned with ethyl ether for 8 h) and the treated hair tress. Adapted holder _•.,•. ' . _ • ' ' : •: .... -- •. ,d•.d. -' '.• • • • ':•.• :• • ': .•'• •'•' '• ,' • •- '•:-0:• -•:• ::'•'•: ß ' C•ent hold• Figure 1. Illustration of the adapted holder used in the diffuse-reflectance measurements aperture

292 JOURNAL OF COSMETIC SCIENCE Cumulative treatments. In this experiment a more damaged dark-brown (DD-B) hair tress was treated with two different formulations obtained from Ind. Corn. Cosm•ticos Natura Ltda., Itapecerica da Serra/SP, Brazil. The tress was divided into three samples (DD-B1, DD-B2, and DD-B3) and rinsed with 1 ml of the formulation for 2 min, washed with water at 40øC for 1 min, combed, and left to dry at room temperature for 3 h before the measurements. This procedure was repeated four times every two days. After thirty days the fifth washing and measurements were done. Treated hair was stored in a desiccator during the intervals. Influence of reference (zero difference) and statistical analyses. The aim of this ex- periment was to evaluate the use of an external or an internal reference (zero difference) to calculate the color difference parameters. A less damaged black hair (B) tress was cleaned by extraction in ethyl alcohol for 8 h (external reference), divided into five samples of 2 g (B1, B2, B3, B4, and B5), and extracted again in commercial ethanol for 8 h. Table II shows the treatments that were done on the samples. RESULTS AND DISCUSSION EXPERIMENTAL OPTIMIZATION Position, viewing angle, and viewing area of the sample. These measurements were done to find the better instrumental operating conditions for human hair samples. Table III shows the average results of L*, a*, and b* parameters obtained with different instru- mental configurations. As observed in Table III, there is no significant difference among the average color values for sample position, viewing angle, and viewing aperture. Based on these results, the following instrumental conditions were chosen for the next experi- ments: horizontal position, a viewing angle of 10 ø, and a viewing aperture of 5 x 10 mm. Influence of sample color, texture, and geometry. The next step was to evaluate the instru- mental sensitivity for samples of different color, texture, and geometry, including or excluding the specular component, as shown in Table IV. As expected, the exclusion of Table II Treatments in Less Damaged Black Hair (B) Samples Samples Treatments B1 B2 B3 B4 B5 Ethanol PA/8 h, ethanol commercial/8 h, and Neutrox © conditioner Ethanol PA/8 h, ethanol commercial/8 h (a), ethanol PA/8 h, and ethanol commercial/8 h (b) Ethanol PA/8 h, Neutrox © conditioner, ethanol commercial/40 min, shampoo + Neutrox © 1 ø (first wash), shampoo + Neutrox © 2 ø (second wash), and shampoo + Neutrox © 3 ø (third wash) Ethanol PA/8 h + Neutrox © conditioner Ethanol PA/8 h + Neutrox © conditioner Operating conditions: D65 illuminant, 10 ø viewing angle, 5 x 10 mm viewing aperture, and adapted holder were used. Sets of ten diffuse reflectance measurements were done. Internal reference was chosen among a set of ten readings, taking the closet L*, a*, b* (CIELAB) and X, Y, Z (FMCII) values to the average value in each treatment.