MEASUREMENT OF HAIR LUSTER 295 Results obtained for the three samples (DB-1, DB-2, and D-B3) were reproducible. A maximum estimated standard deviation of 12% was observed in coordinate parameters (L*, a*, b* and X, Y, Z) except for L* (lightness), which was 4.5%. Table V! shows an example of quintuplicate measurements and averages obtained after soap treatment in the CIELAB system. Values of DC* (chromaticity difference) and DL* (lightness dif- ference), for both systems, showed a high estimated standard deviation, hindering them in quantifying luster. DE* (color difference) showed the lowest error range among color parameter values. Figure 2 shows DE, DE* (color difference) values obtained, after the treatments de- scribed in Methods, for the CIELAB and FMCII systems. These values were sensitive to the different treatments. The brilliantine treatment showed the highest DE (FMCII) value. Visual observation of the treated tresses and the reference (ethyl ether/8 h) tress showed a darkening and an increase in luster after brilliantine treatment, agreeing with the decrease observed in L*, L (lightness) values and the significant increase in the DE, DE* values. The overall data indicates DE*, DE as the most sensitive color parameter for means luster. CUMULATIVE TREATMENTS Diffuse reflectance measurements were done after every sequential treatment, as de- scribed in Methods. As an example of the data obtained, Figure 3 shows the average DE values in cumulative treatments with standard and PQ7 formulations (the graph shape is similar in the CIELAB system, although DE values were lower). As seen, DE values tend to increase after each treatment sequence. This was observed in every case, but especially with the PQ7 formulation, meaning that no luster saturation was attained. After 30 days (fifth wash), the color-difference values decreased, being lower than those obtained after the first wash. This may point to a hair-surface modification during storage. The color-difference parameter (DE) again showed the highest sensitivity to discriminate among the treatments. Table VI Quintuplicate Measurements of the CIELAB System Parameters L*, a*, and b* and the Calculated Parameters DL*, DC*, and DE*, Obtained With Sample D-B1 Treated With Commercial Soap Readings L* a* b* DL* DC* DE* 1 22.49 4.09 4.75 -0.92 -0.21 1.04 2 23.27 4.19 4.97 -0.14 0.02 0.39 3 23.11 3.95 4.96 -0.30 -0.14 0.38 4 22.49 4.05 5.43 -0.92 0.30 0.97 5 22.31 4.07 5.23 -1.10 0.15 1.11 Average 22.73 4.07 5.07 -0.68 0.02 0.78 Estimated standard deviation 0.38 0.09 0.26 0.38 0.19 0.32 % Deviation 1.68 2.11 5.22 -56.43 776.66 41.64 Operating conditions: horizontal sample position, D65 illuminant, 10 ø viewing angle, 5 x 10-mm viewing aperture, and adapted holder. CIELAB system parameters: L* (lightness coordinate), a* (red-green coordinate), b* (blue-yellow coordi- nate), DL* (lightness difference), DC* (chromaticity difference), and DE* (color difference). Reference tress (ethyl ether/8 h) and sample D-B 1 (dark-brown hair) were used.

296 JOURNAL OF COSMETIC SCIENCE o lO 6 4 2 0 water soap brilhantine D-B1 T I I CIELAB FMCi1 D-B2 D-B3 hair sample Figure 2. Average of color-difference values obtained after treatments in the dark-brown hair. Samples D-B1, D-B2, and D-B3. Treatments: water 350-40 ø C (grey bar), commercial soap (black bar), and brilliantine (white bar). Quintuplicate measurements. D65 illuminant. 10 ø viewing angle. 5 x 10-mm viewing aperture. Reference tress: dark-brown hair treated with ethyl ether/8 h. CIELAB and FMCII systems. ESTABLISHING THE LUSTER SCALE Diffuse reflectance measurements were done in black hair tress (B) samples treated as described in Methods. Color differences (DL*, DC*, DE* and DL, DC, DE) were calculated using internal (color-parameter values measured for every sample before the treatments) and external (color-parameter values measured for the tress before the treat- ments) references. All samples came from the same tress. Internal and external references were chosen based on the L*, a*, b* (CIELAB) and X, Y, Z (FMCII) values. The inter- nal reference data was chosen by taking the value closest to the average among a set of ten measurements. These values were taken from the diffuse reflectance data of each of the alcohol-treated samples of the tress. The external reference was chosen among the