Conventional pearlescent pigments consist of a transparent platelet-like substrate, preferably of low refractive index, which is coated with a minimum of one high-refractive-index material. Typical low-refractive substrates are mica, synthetic mica, alumina, glass, silica, and the like. Corresponding high-refractive materials for the surrounding coating are titanium dioxide, iron oxides, tin oxide, and mixtures thereof [2]. This coating, too, can comprise several alternating layers of high- and low-refractive materials, with, for example, alumina, silica, or silica modifications serving as low-refractive intermediate layers [3]. Multilayer pearlescent pigments can provide attractive and improved colour properties, compared with single-layer-type products, but their performance in ...