EFFECTS OF THE CUTICLE ON THE PERMANENT WAVE SET OF HUMAN HAIR

A significant inhibitory effect of the cuticle on the permanent wave s et of human hair was confirmed by measuring the set of fiber loops for both descaled (cuticle-removed) and normal (cuticle-unremoved) hairs. The analysis of fiber set, based on the theory established in a previ ous investigation (7), showed that the set obtained for both types of hair is in the same way related to the relaxation of fiber bending sti ffness during reduction. The consideration of the differences between the bending relaxation rate of normal and descaled hairs during reduct ion suggests that the main role of the cuticle in waving is to reduce the setting ability of human hair by effectively operating as a chemic al barrier. It lowers the concentration of the reducing agent through reaction prior to its diffusion into the fiber cortex. A further, mino r, and mechanical role of the cuticle for permanent set is discussed.