CONFOCAL 3D RECONSTRUCTION OF HAIR 7 Figure 7. Cosmetic treatments: a) permanent waving b) bleaching. tances confirmed the loss of material. A less-uniform brightness confirmed the chemical degradation of the cuticle. Swelling in water (Figure 8) led to bulging of the surface. The altitude profile showed large undulations with a period of about 34 I•m (4-5 cells) and an amplitude of about 0.8 I•m. There was no accompanying lifting of the cuticular cells. Urea (Figure 9) had a more drastic swelling effect, with a shorter period (15 I•m) but a higher amplitude (2.6 I•m). This periodic bulging of the surface could be explained by local resistance of the cuticle to the pressure exerted by a turgid cortex. The effect of stretching is clearly observed in Figures 10ad. The limited number of optical sections used in this experiment reduced the vertical (Z) resolution to 0.5 I•m, and consequently the periodicity of the cuticle could not be observed. Nevertheless, the increased brightness of the cuticular cell border showed that the cells rose with an extension of as little as 10%. This was accompanied by sliding and, in the example shown, local cracks in the cuticle. When such cracks appeared, sliding and rising of neighboring cells was not seen. At 20% extension, the altitude profile indicated that cracking reached a depth of about 4 I•m and involved the whole thickness of the cuticle.

8 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 8. Swelling in water. Waviness is clearly drawn on the profile (scales as in Figure 6). The flat bottom of the pit in the profile suggested that the crack was limited to the cuticle and did not thus involve the cortex. HAIR VOLUME EXPERIMENTS Staining with rhodamin B in water. The fluorochrome stained the free border of cuticular cells (Figure 1 la). The vertical optical cross section (Figure 1 lb) showed that it did not penetrate into the cortex. No internal structures were visible. The cuticular envelope drew exactly the cross-sectional shape of the hair. A fair autofluorescence of the adhesive can be seen on each side of the hair section. Staining with octadecyl rhodamin in ethanol:water. This fluorochrome penetrated through the cuticle into the cortex, selectively staining membrane components and giving high-definition images of the cortex. The optical section 20 Ixm below the surface (Figure 12a) showed cuticular cells at the periphery and highly fluorescent cortical cells with a typical fusiform shape within a network of fibrous keratin bundles. The axial optical section (Figure 12b), taken 40 Ixm below the surface, showed that rhodamin Figure 9. Swelling in urea. Note the bulged aspect of the surface (scales as in Figure 6).