2001 ANNUAL SCIENTIFIC MEETING 135 OPTICAL PROPERTIES OF HAIR- EFFECT OF TREATMENTS ON LUSTER AS QUANTIFIED BY IMAGE ANALYSIS R. McMullen and J. Jachowicz International Specialty Products, Wayne, N J, USA Introduction The attribute of hair luster has been a significant concern to the consumer and marketers for quite some time, especially recently due to the proliferation of reactive and damaging hair treatments. Luster is commonly defined as the ability of a given material to produce a bright reflection. Stature et al. [1,2] employed a goniophotometer and multiple fibers to record light distribution curves necessary to calculate luster parameters. This work was later expanded by Czepluch et al. [3], who constructed a computerized goniophotometer. Reich and Robbins [4] and Bustard et al. [5], who also utilized a goniophotometer, employed single fibers to study the effects of shampooing and dyeing on the luster of hair. Maeda et al. [6] has presented luster measurements performed by using a color image processor. More recently, hair luster was measured using diffuse reflectance spectrophotometry [7]. The objective of this work was to reassesss the effect of various hair treatments, including selected polymers and oils, on hair luster and deternfine the mechanism of the observed luster enhancement or reduction. Materials & Methods Luster analysis was performed on natural white, light blonde, light brown, medium brown, and dark brown hair purchased from IHI & Products, Inc. (Valhalla, NY). An Olympus Camedia El0, with a resolution of 4 megapixels, was employed as the image collection device for all studies presented in this report. Image analysis was carried out using the software, Sigma Scan Pro 5.0 (SPSS), which enabled us to obtain light intensity (luminance) distributions along a given hair tress (Figure 1). The data were further analyzed by integrating the area under the luminance curves in order to obtain values of luster parameters. We also utilized the image analysis software, Image Tool 2.0, in order to analyze reflection patterns from African hair [8]. Hair treatments included polymers, oils, and pigments such as Ethyl Ester of PVM/MA Copolymer, Vinyl Caprolactam/PVP/ Dimethylaminoethyl Methacrylate Copolymer, Isobutylene/Ethylmaleimide/ Hydroxyethylmaleimide Copolymer, Phenyl Trimethicone, Amodimethicone, Castor Oil, and ZnO. Results & Discussion Every measurement set consisted of obtaining an image of two untreated tresses on the cylinder mount followed by treatment of one of the tresses with an investigated solution. The second tress served as an internal control. We then examined the difference, before and after treatment, for the treated tress. A plot of luminance as a function of distance along the hair tress is provided in Figure 2, which shows specular curves corresponding to the reflected light from the dark brown hair. Also shown in Figure 2 are estimated diffuse reflection curves in which the endpoints of the specular reflection curves are used to generate a diffuse reflection curve. While we were able to obtain true diffuse reflection curves by using linear polarizers, the method of diffuse reflection estimation, devised by Stature et al. [1,2], provided results that correlated much better with human panel test evaluations. By determining the area under the specular (S) and diffuse (D) curves, we were then able to calculate luster parameters based on the equations shown below. Ls ....... _ S - D s ..... (1) LRooO n, = S (2) S Ds ..... * Similar to reports by Stammet al. [1,2], we found that the use of Equation 1 leads to larger differences in luster values for different hair types and hair treatments. Reich and Robbins [5] determined the diffuse reflection in the same mmtner as Stamm et al.,

136 JOURNAL OF COSMETIC SCIENCE however, they utilized a different relationship to define luster as shown in Equation 2., where W•/2 represents the width of the specular peak at half of its maximum intensity. The results were generally consistent with the literature data and visual observations. It was shown that: Repeated measurements of various tresses of untreated hair yielded the following values of luster parameters for exposure settings of f8 and 1/13 s: Lst,,,,,, = 0.71 _+ 0.025 and LRot, t, ins= 0.027 + 0.002. Piedmont, Light Blonde, Light Brown, Medium Brown, and Dark Brown Hair showed a gradual increase in luster proportional to the content of melanin pigmentation. Light colored hair displayed clearly two specular reflection bands corresponding to the front and back face reflections from hair fibers as reported earlier [1,2]. Silicone and hydrocarbon oils, such as Phenyl Trimethicone, Amodimethicone, and Castor Oil, increase the luster of hair by enhancing the contrast between specular and diffuse areas on hair. Phenyl Trimethicone was found to be the most effective treatment. Luster can be increased by deposition of polymers, such as hairspray or styling resins, forming thin films on the hair surface. A controlled reduction in hair luster can be achieved by deposition of various amounts of micronized ZnO, which increases the width and intensity of both specular and diffuse reflection from hair. References: [!] R.F. Stature, M.L. Garcia, and J.J. Fuchs, d. Soc. Cosmet. Chem., 28, 571-599 (1977). [2] R.F. Stature, M.L Garcm, and J.J. Fuchs, d. Soc Cosmet. Cbem., 28, 571-599 0977). [3] W. Czcpluch, G. Hohm, and K. Tolkicbn, d. Soc. Costact. Chem., 44, 299-318 0993). [4] H.K. Bustard and R.W. Smith, htt. d. Costlier. Sci., 12, 121-133 0990). [5] C. Reich and C.R. Robbins, d. Soc. Cosmet. Chenl., 44, 221 0993). [6] T. Maeda, T. Hara, M. Okada, and H. Watanabe, 16 th IFSCC Congress, New York, 1990, Preprints, Vol. I, p.127. [7] C. Scanavcz, M. Zoega, A. Bm'bosa, and I. Joekes, d. Cosmet. Sci., 51,289-302 (2000). [8] Available l¾om The University ofTcxas Ileahh Scicnce Center in San Antonio. ! 1,50 0 0 10 20 30 40 Distance (rnrn) Figure 1. Digital image obtained for untreated dark brown hair. The red lines illustrate the image analysis procedure employed to determine light intensity as a function of tress length. Figure 2. Light distribution curve showing light intensity (luminarice) as a function of distance along the hair tress for two different tresses.