Inks with special structures that create their color impression in part or whole by their physical structure and not by their dyes or pigments.
Such inks can contain elements that selectively reflect light of a certain wavelength with the aid of interference effects.
Textured inks create shimmering color effects that can vary, depending on the viewing angle. This kind of color generation has its model in nature, where it is found in insects and some species of birds.
It cannot be reproduced by conventional means, which is why textured inks are often used for documents where forgery protection is desired.