To make paper currency they use mixed dyes of special composition. Only a spectrum analysis of dye (which is done in some specific, specially selected spectrum ranges) permits to precisely define colours ratio parameters and to detect a counterfeit bank note printed by a counterfeit dye.

At bank notes and other securities printing they use fluorescent dyes, i.e., dyes capable to glow under exposure to UV-radiation. To give a dye such a property, they add special components into it - luminescent solids that do not glow in natural light, but under exposure to UV-radiation there appears luminescence of one or other colour called fluorescence.

During bank notes printing they use dyes with magnetic properties that appear after adding some ferromagnetic components into a dye. Such a dye can be detected by means of magnetic image visualizers or by testers with magnetic head. They often print serial numbers or fragments of metallographic picture with a magnetic dye.

In modern bank notes they widely use dyes which are perceived at sight as dyes of the same colour but have different reflection in infra-red spectrum range. Such an effect is called as IR-metamerism of dyes. If a drawing is made with two dyes identical in hue but different in properties, than in IR-range of spectrum one will see only a part of the whole drawing corresponding to the zone coated with the dye reflecting IR-rays.