344 JOURNAL OF COSMETIC SCIENCE untreated Castor Oil Amodimethicone Phenyl Trimethicone Figure 8. Images of hair treated with various oils. Exposure values: fS, 1/6 s. 250 • untreated ß o 200 o 150 E 3•100 50 i i i ! 0 10 2o 30 40 50 Distance (ram) Figure 9. Light-scattering curves for untreated and phenyl trimethicone-treated hair. light-scattering peak. Similar widening is not noticeable in the light-scattering curve obtained for untreated hair. All three investigated compounds displayed a similar effect, although, for the sake of brevity, relevant light-scattering plots are not presented in the paper. The values of luster parameters, calculated according to the previously discussed

LUSTER QUANTIFICATION OF HAIR 345 equations, are gathered in Table II and suggest increases in hair gloss, as compared to untreated hair, for all three of the oil treatments. As pointed out previously, the N½ luster parameters calculated for oil-treated hair are not substantially different from those obtained for untreated hair. Actually, the numbers corresponding to oil-modified hair are slightly smaller, indicating no shining effect or even a small reduction in luster. It is also obvious that treatment of hair with oil leads to a reduction in the maximum intensity of the specular reflection. However, the Lsta,•, • and LReic3_Robbin • luster parameters, which utilize the quantity Dsta,•, • for diffuse reflection (calculated as the area under the straight line connecting the ends of the light distri- bution curve), substantiate significant increases in the calculated luster parameters. The reason for this is that Dstam m accounts for the darkening effects of the treatments that provide more contrast between the specular band and the background (diffuse area of the hair tress). POLYMER-TREATED HAIR Polymers are believed to increase the luster of hair when used as film formers in hairsprays, hair gels, or special hair glazes. We have tested a series of polymers (see Schemes 4-6 for structures of these compounds), frequently employed as fixatives, by their deposition on dark brown hair using 2% ethanol solutions. The treatments were applied uniformly to the surface of the hair to assure thin film formation. It should be stressed that the same polymers applied as dispersions or emulsions, or in mixtures with incompatible ingredients, may not form uniform and homogenous films, leading to a reduction in intensity and a broadening of specular reflection. Figure 10 shows the images of untreated and treated fibers obtained by using exposure parameters of f8 and 1/6 s. As in the case of oil treatments, an apparent increase in luster is due to an enhancement in contrast between the specular and diffuse reflection areas as a result of darkening in the region of the tress corresponding to diffuse reflection. This is further illustrated by the light distribution curves obtained for one of the investigated polymers, vinyl caprolactam/PVP/dimethylaminoethyl methacrylate copolymer (Figure 11). The curves corresponding to polymer-modified hair show a shift of the specular reflection as compared to untreated hair and a decrease in diffuse light intensity, i.e., at the regions peripheral to the reflection band. A shift along the distance axis can likely be ascribed to the evening of the fiber surface by a polymer film, thus minimizing the effect of cuticle inclination. On the other hand, a decrease in the intensity of diffuse light leads to an increase in the calculated luster parameters, as shown in Table III. The results of calculations for polymer-treated hair reveal increases in luster parameters, with LRac•_•o•in • and Lstam m providing the largest differences as compared to untreated Table II Calculated Luster Parameters for Hair Treated With Various Oils (f8 1/6 s) Treatment Peak intensity N½ L•3•o• • L s ...... Untreated 168 + 4 0.80 + 0.02 0.54 + 0.07 0.72 ñ 0.03 Castor oil 141 _+ 9 0.79 0.59 + 0.19 0.79 + 0.05 Amodimethicone 144 + 5 0.75 0.82 + 0.05 0.85 + 0.01 Phenyl trimethicone 154 _+ 1 0.78 0.62 + 0.10 0.80 + 0.03