CATIONIC CONDITIONING COMPOUNDS 65 unextended hair fiber. The types of scale lifting observed during these extensions are: (B) the start of random scale edge lifting and a brilliant line at the scale edge, (C) scale edge lifting that has become a common occurrence, and (D) extreme scale edge lifting in frequency and angle. Finally, hair fiber breakage occurs. Figure 1 depicts typical ex- amples of hair fibers observed in autofluorescence in the microspectrophotometer prior to extension (a) and at highest levels of extension, showing extreme scale edge lifting (b). The extensions at which the specific levels of scale lifting and fiber failure occur were recorded and are presented in graphs. SEa4. A Hitachi S-4500 digital field emission SEM was used for a detailed topographical study of the longitudinally viewed hair fibers. Untreated hair fibers and fibers treated once and ten times with the respective MCCs (before and after extension to failure) were mounted on SEM stubs on double-sided tape and coated with 100 /• of platinum. Scanning electron microscopy with its higher magnifications of the fiber's topography will reveal whether and how these conditioning compounds affect the stress release mechanisms during extension. Figure 1. Hair fibers observed in autofluorescence in the optical microscope prior to extension (a) and at highest levels of extension, showing extreme scale edge lifting (b).

66 JOURNAL OF COSMETIC SCIENCE For the ease of understanding the scale-lifting phenomena, SEM views display the typical appearance of the cuticula of unaltered hair fibers prior to extension (A) and at various extension levels showing the specific scale-lifting phenomena (B, C, D) that occur in response to the stresses imposed on the cuticula during extension. For that purpose, the hair fibers were mounted in the extended state onto the tape on SEM stubs for viewing in the SEM. The first step in this study was to show the typical appearance of surface cuticle cells of (A) unaltered/untreated hair fibers prior to extension (Figure 2a,b). Typical examples of the (B) random, (C) common and (D) extreme scale-lifting phe- nomena are shown in Figure 2c, Figure 2d,e, and Figure 2f h, respectively. The dry conditions in the SEM may enhance and freeze the state of the lifted cuticle cell edges. Irrespective of the differences in their appearance, the SEMs show impairment of inter- cellular adhesion. RESULTS AND DISCUSSION MCCs AND KERATIN Cationic compounds are important ingredients in shampoos, rinses, and conditioning '70e007 5.0 kV b60803 ß ... •. c•eaeas s.e ,v xee•' '•i•' •s. d•eaeas s.e ,v x•.eik"•e:•' •s, Figure 2. (a,b) Typical appearance of surface cuticle cells of (A) un•tered/untreated hair fibers prior to extension (SEM). (c) Hair fiber showing the start of (B) random scale edge li•ing at low levels of extension (gEM). (•,e) Ilaie •bce• sho, i,• (C)tun .... on •tale edge 1if•g at •ermediate •eveis or' extension (f-h) Hair fibers showing (D) extreme scale edge lifting at high levels of extension (SEM).