70 JOURNAL OF COSMETIC SCIENCE Photo No. :: 24 Time :8:46:32 Figure 2. SEM image of untreated (blank) hair fibers. Cuticle structure is rough and subdued. was degraded due to the alkalinity of the solution. Addition of surfactant on the other hand allowed for the rapid reaction of peroxide with the surface of the hair fiber. The apparent induction time to activity noted in the pH = 9 bleaching treatment is absent or greatly minimized through the inclusion of modest amounts of surfactant in the bleach­ ing formulation. This accelerated activity is attributed to the beneficial effect of surfac­ tancy in removing the hydrocarbon overlayer. The attenuation of the characteristic N & S signals from the hair matrix can be used as a means for estimating the hydrocarbon layer thickness on the hair surface. A number of assumptions need to be made in order to carry out the calculation of overlayer thickness: 1. The substrate surface composition (hair) is taken to be represented by the bulk elemental composition using the relative abundance of the various amino acids present in the hair. The bulk elemental composition in units of atom percent, excluding hy­ drogen is 52.8% C, 30.8% 0, 14.2% N and 2.3% S. 2. The composition of the overlayer is assumed to be far-like with a representative composition of 95% C and 5% 0. 3. The overlayer is assumed to be continuous and uniform. Using these assumptions and tabulated sensitivity factor and inelastic mean free path data (6,7), the calculation finds a layer of approximately 30 Angstroms would yield the observed blank sample surface composition. Microscopic examination of the hair following the 3% hydrogen peroxide, pH = 9, sur-

N(E) Min: 52 Max: 37263 0(1s) 602 541.8 481.6 HAIR SURF ACE CHEMISTRY 71 C(1s) S(2s) S(2p) 421.4 361.2 301 240.8 180.6 120.4 60.2 -4.57764e-005 Binding Energy (eV) Figure 3. Survey scan of bleached hair. Table II Surface Composition Before and After Bleaching Treatment (3% hydrogen peroxide, at pH 9 for 45 minutes) Element Blank Bleached C 76.8 67.5 N 6.8 10.8 0 12.4 18.3 s 2.4 2.8 Low levels of Si and Ca commonly observed not included in the table. factant, 45 min. procedure show a generally more uniform, cleaner, and sharply defined surface structure (Figure 7). The raggedness of the cuticle edges is not as extreme, and the random debris observed on the blank hair is gone. The overall general appearance of the cuticle structure is clearer in keeping with the removal of the overlayer. CONDITIONER-TREATED HAIR The conditioner treated hair showed several dramatic changes in surface compos1t10n relative to the bleached surface. First was the great increase in the amount of Si present on the surface due to the dimenthicone in the formulation. The amount of nitrogen detected at the surface decreased significantly, while the surface oxygen content in­ creased (Figure 8). The comparison of surface compositions from bleached to treated is summarized in Table III.