New Hair Evaluation Method by Hair Diameter Profile

Abstract

Hair diameter is one of the most basic hair properties and is considered to be closely related to sensory evaluation of a hair bundle: however, the fluctuation of hair diameter in the length direction has not been studied very much. In this study, the fluctuation of hair diameter in the length direction was measured with the cross section of the hair as an elliptical shape, and the relation with the sensory evaluation was investigated. Precise and two-dimensional fluctuation of hair diameter was expressed for the first time in the form of “hair diameter profile” from the data that measured 400 points of hair diameter at intervals of 0.125 mm in the length direction of the hair. It was found that the hair diameter fluctuated by 3.8% on average even in a strand of hair, and the major axis angle also changed. Therefore, the torsional hair was visually and quantitatively expressed using a parameter of the accumulated major axis angle. As the result of acquiring hair diameter profiles and sensory evaluation on four types of hair with different characteristics, the larger the standard deviation of the average diameter and the degree of the major axis angle, the lower the scores of various sensory evaluations were found to be. There was a certain correlation between the hair diameter profile and the sensory evaluation, which suggested that hair diameter profile might be useful to evaluate total hair characteristics.