The first theories to explain color go back to the 17th century. It is above all a function of physics and the interaction of light with matter on the level of electrons and the shape of an object. For decades, L'Oréal's researchers deepened their knowledge in this domain, to develop new applications in hair coloring and make-up.
A new-generation make up
Among their latest advances: photonic make-up. This make-up, which is colorless or white in appearance, becomes colored and iridescent when applied to the skin which contains a pigment, melanin. In theory, it is easy to imagine structures (multilayered, networks or crystals) of white or colorless matter that appear colored under the effect of light. But how can they be fabricated and formulated in a make-up product to reproduce, on nails or eyelids, the delicate iridescence of an opal or the carapace of a scarab beetle? To do that, the researchers have simply copied the structures found in nature and made multilayers of mica, silica, networks of polymers or silica beads. And they played with the number of layers to produce different effects. With a simple thin layer, they obtained an iridescent effect, or in other words a color that changes with the angle of observation. By multiplying the layers of particles or metallic oxides (up to 200 layers!), they produced a mirror effect, with the color of the light transmitted being complementary to the light reflected.