EVALUATION OF HAIR DAMAGE 363 No Perm • Perm 2 Perms 3 Perms Unbleached Hair No Perm • Perm 2 Perms 3 Perms Bleached Hair Figure 10. Force-extension curves for hair with repeated perm treatments.

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