Interference pigments are among the most optically sophisticated pigments. Unlike colored pigments that absorb some of the incident light and metallic pigments that reflect the incident light, interference pigments involve superimposed light waves that are shifted together due to reflections and refractions, thereby causing strengthening or weakening of the resulting light wave. Various factors such as the layout of the pigment, its application and the lighting make for optimum conditions.
Pigments manufactured with wet chemistry generally have a carrier platelet of natural mica, silicon dioxide or aluminum oxide. High refractive metal oxides such as titanium dioxide or iron oxide are applied to this carrier platelet. Due to different layer thicknesses of titanium dioxide, these pigments change their color from white, yellow, red or blue to green. This unusual color shift results from the fact that the maximums - and also the minimums - move to longer wavelengths. For yellow, the minimum shifts from the UV range into the visible region, whereby white turns into a yellow. This minimum shifts further into the longer wavelengths with increasing layer thickness of the titanium dioxide, which results in a red. The maxima following the minimum in the UV range migrates into the visible range, while the maximum in the long wavelength range travels into the invisible infrared range. With higher layer thickness the blue maximum shifts into the green range. Such pigment group color sequences are thus chemically identical, differing only in the layer thickness (Figure 1).