Relationship between the Sensory Evaluation of Stiffness and Bending Stiffness Distribution Curve of the Fiber Components of a Hair Tress

Abstract

We performed a sensory evaluation of the stiffness of aged hair and damaged hair, and examined the relationship between the obtained sensory evaluation and the bending stiffness distribution curve of the whole hair tress. We used a mixture of gray and black hair as an aged hair tress, and of bleached and permed hair as damaged hair tresses. The results indicated a difference in sensory evaluation of stiffness between the gray and black hair tresses and a difference in the high-rigidity range (85% – 100%) in the bending stiffness distribution curve. A difference was observed in sensory evaluation of stiffness between the different damaged hair tresses. However, chemical treatments resulted in changes in both the low- and high-rigidity regions in the bending stiffness distribution curve. We attempted to find the area of highest correlation between the distribution curve and the sensory evaluation. The distribution curve was divided into several areas and the stiffness average was calculated for each area. We then calculated the correlation coefficient with the sensory evaluation. The results indicated that the area with the top 10% – 15% stiffness of the distribution curve was most closely correlated to the sensory evaluation.