Colour extension properties of individual pigments and effects on shades of foundations in cake form.

Synopsis The mechanism of colour change during the pigment dispersion process and during powder application to the skin surface was studied by examining the colour extension properties of Yellow. Red, and Black iron oxides in white powder bases. A new measure for the evaluation of the degree of colour extension was devised. This measure corresponded well with human visual sensation, and was found to be useful for comparing the rates of colour extension of pigments. The rate of colour extension of pigments was found to vary in the order: Yellowacicular Redgranular RedBlack. This result explains colour darkening and the change towards reddish tones during the pigment dispersion process, because Yellow extends fully in the early stage of the process but Red, especially in granular form, and Black continue to extend even in the later stage. Acicular Red iron oxide is more favourably employed than the granular form to attain sufficient colour extension of foundations with lower energy expenditure, and to decrease the discrepancy between the cake colour and the colour of applied powder.