Evaluation of Sense of Use Properties for Cosmetic Powders with Surface Treatment by Using Direct Shear Testing of Powder Bed

Abstract

In the cosmetic field, surface treatment for cosmetic powders has been used for the purpose of product stability, functionality and sense of use improving. The various treated powders are applied to powdery cosmetics such as powdery foundation in order to add the required texture. However, objective evaluation methods about sense of use for each treated powder have not been systematized. In this study, we investigated the correlation between sense of use and physical properties obtained from direct shear testing of the powder bed about four kinds of sericite powder with different surface treatment methods. As a result, internal friction coefficient μ_i and shearing cohesion τ_c were correlated with the smoothness and the moist feeling, respectively. Furthermore, it was found that the softness of surface treatment powder can be estimated by the value of stress relaxation ratio σ_srr obtained from relaxation process after powder consolidation.