The bulk powder behavior between four types of spherical
silica powders-porous and nonporous silica with and without
the removal of surface-adhered nanoparticles by ultrasonic
cleaning-and surface-cleaned mica powder was characterized
by two types of measurement methods: friction behavior and
cohesive behavior. Fig. 3(a) shows the schematic diagrams of
the friction tester (Kato Tech Co., Ltd., KES-SE). The principle
of measurement of the friction tester has been reported by
Kondo [5]. Generally, in the cosmetic industry, this method has
been employed to measure the bulk behavior of cosmetic raw
materials and products [6].