364 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Untreated Log Cum. Failure 0.00 ß -0.25 -0.50 -0.75 ß -1.00 -1.25 -1.50 -1.75 -2.00 ß Hair ' I I ' 1 ' I ' 0 1 0 2 3 4 5 Log Cycles 2 3 4 5 Log Cycles I Perm Log Cum. Failure 0.00 -0.25 -0.50 -0.75 -1.00 -1.25 -1.50 -1.75 /• -2.00 ß , ß 1 2 Perms Log Cum. Failure 0.00 -0.25 -0.50 -0.75 -1.00 -1.25 -1.50 -1.75 -2.00 3 Perms Log Cum. Failure 0.00 -0.25 -0.50 -0.75 -1.00 -1.25 -1.50 -1.75 -2.00 0 1 2 3 4 5 0 1 2 3 4 Log Cycles Log Cycles Figure 11. Fatigue lifetime data for untreated hair and three subsequent perm treatments. Furthermore, the possibility must be considered that cosmetic treatments, especially those involving exposure to chemicals, leave the substrate more susceptible to further damage during subsequent grooming. Our goal was to establish whether subsequent grooming procedures caused secondary damage, and whether the inclusion of a condi- tioner could prevent or at least alleviate some of the mechanical or abrasive damage experienced during combing. Surface changes Microfluorometry. Our experience with the fluorescent tracer Rhodamine B in connection with hair fibers has shown that this molecule is a useful detector of damage to the

EVALUATION OF HAIR DAMAGE 365 Table VII Fatigue Behavior of Modified Hair (60 Specimens) Unbleached hair Bleached hair No. of hf Slope No. of hf Slope No. of perms (x 10 3) (X 10 - •) survivors (X 10 3) ( X 10 - •) survivors 0 '100+ 5.0 -+ 0.52 40 '100+ 3.1 -+ 0.22 39 1 '100+ 3.1 -+ 0.25 43 78 1.8 -+ 0.17 27 2 6 1.7 - 0.18 26 0.6 1.9 + 0.23 16 3 3 1.1 + 0.98 13 3 1.5 --- 0.12 13 * Indicates that at 100,000 cycles, fewer than half of the fibers broke. cuticular region, especially to the scale face of the outermost cuticle. Since oxidative treatments produce sulfonic acid groups in hair fibers and Rhodamine B is a cationic dye, this fluorescent molecule is ideal for measuring the extent of oxidative damage. Longitudinal fluorescence intensity scans showed the expected major difference between the unbleached and bleached categories. However, differences due to grooming proce- dures within each of the three groups were slight and within the range of experimental error. Scanning electron microscopy. Even unbleached hair appears to have suffered damage when repeated combing occurred without prior shampooing and conditioning. As seen in Figure 12, cracks, holes, and debris from broken-off cuticles are seen in practically all hair fibers subjected to the combing procedure. Such damage due to combing is much more apparent in hair that had been bleached ten times for two minutes. Scales seem to become detached and brittle, resulting in frag- mentation at the edges and deposition of the debris near the scale edge, as shown in Figure 12. Thinning of the surface c&icles, a characteristic feature in the four-hour oxidized hair, appears to be much more pronounced than in the 10 X 2' bleached sample. The longer bleaching treatment, producing thinner and more swellable cuticle cells, may have rendered these fibers somewhat more pliable during the wet combing and thus less susceptible to damage. The combination of shampooing and conditioning prior to combing appears to be responsible for less severe and less frequent damage to the surface cuticles of unbleached and bleached hair, as seen in Figure 12. As would be expected, the debris of the fractured cuticles has been removed during the shampooing, conditioning, and rinsing procedures. While cracks, holes, and broken-off cuticles are still present, they are definitely less frequent, and regions with intact cuticles are more common. Shampooing and conditioning appears to result in the deposition of a protective layer of conditioners, rendering the hair fiber more manageable and less likely to fragment during subsequent combing. The shampooed/conditioned/combed hair fibers resembled the corresponding samples prior to the multiple grooming procedures. Wettability. The effects of the various grooming procedures on the surface properties of hair were explored by determining the wettability of the fibers before and after the treatments. In evaluating changes in wettability, it has to be kept in mind that while mechanical abrasion is the major factor in combing by itself, shampooing and condi-