Effect of Color Extension Behavior of Individual Pigments on Shades of Foundations in Cake Form

Abstract

In order to obtain a excellent-quality foundation, it is important that the shade of the foundation applied to the skin corresponds well to the cake color. However, the shade of applied foundation tends to shift toward a more reddish tone than the cake color. Also the color-shift toward reddish tone is generally observed during the pigment dispersion process. We investigated the causes of these color changes from a view point of color extension properties of RED, YELLOW and BLACK iron oxides.
Powders and oils were mixed in a laboratory grinding machine after mixing with a household mixer, and the mixture was taken at intervals and pressed. Evaluation of the shades of applied foundation samples was performed by applying the powders to white porous polyvinylalcohol sheets. Samples were applied to the sheets by using dry applicator with weak, medium or strong shear. Color measurement was made by using a spectrophotometric colorimeter.
Application tests and microscopic examinations suggest that further color extension occurs during application of foundation, and this color extension results in the discrepancy between the cake color and the color of applied powder. A new measure for the evaluation of the degree of color extension was devised. This measure was confirmed to correspond well to human visual sensation, and was found to be useful for comparing the rates of color extension of pigments. The rate of color extension varied in the order: YELLOW<acicular RED<granular RED<BLACK at respective pigment concentrations similar to those in foundations. This result explains color darkening and changing toward reddish tones during the pigment dispersion process or during application, because YELLOW extends fully in early stage of the process but RED, especially in granular form, and BLACK continue to extend even in the late stage or during application. Acicular iron oxides extend more rapidly, because their aggregate structure is bulkier and looser than that of granular ones.
Acicular RED iron oxide is therefore more favorably employed to attain sufficient color extension of foundation with lower energy expenditure, and to minimize the discrepancy between cake color and the color of applied powder.