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This invention deals with colore d nacreous pigmen ts and with processes for producing these pigmen ts.

Nacreous pigmen ts produce pearl-like, metallic, and iridescent effects. A widely used type comprises muscovite mica platelets coated with a metallic oxide, such as titanium dioxide. A relatively thin titanium dioxide coating produces a pearl-like or silvery luster. Mica platelets with thicker coatings produce color< /span>, even though the components are colorless, through the phenomenon of light interference; they are known as interference pigmen ts. The color< /span>, called the reflection color< /span>, is seen most effectively by specular or mirror-like reflection, where the angle of reflection equals the angle of incidence. The reflection color< /span> is a function of optical thickness, i.e. the geometrical thickness times the refractive index, of the coating. Optical thickness of about 80 nm to about 140 nm produce reflections which may be called white, silvery or pearly; optical thickness of about 190 nm or more produce colore d reflections.