ESTIMATION OF THE RATE OF SHEAR ENCOUNTERED IN TOPICAL APPLICATION OF COSMETICS

The rates of shear encountered in topical application of cosmetic creams and lipstick were obtained by dividing the application velocities, at which the samples are being sheared, by the applied thicknesses of the layer. The application velocity was measured by means of a high-speed camera. Beauty artists, formulating chemists of cosmetics and women employees were used as the sensory panel. For topical application of creams in make-up, the maximum rates of shear were found to be between 10⁴ and 10⁵ S^-1 , though the rate of shear differed from one kind of cream to another. The maximum rates of shear for lipstick in make-up were smaller than those for creams and were between 10³ and 10⁴ s^-1 .