A filler is a substance consisting of particles that are practically insoluble in the application medium, which is used to increase the volume or improve technical properties and / or change optical properties. The fillers used in coatings and coatings are predominantly light-colored, mainly inorganic powdery substances, inert with respect to this binder, and differ from white pigments in mainly a lower reflection coefficient. They are used for: hardening (reinforcing), improving the mechanical characteristics of coatings (bending strength, adhesion and stress), regulating the gloss of coatings, reducing the cost of coatings. The risk of coating cracking can be significantly reduced by using fibrous or lamellar fillers. The shape and size of the filler particles also affect the rheological behavior of coatings. Like pigments, fillers with strongly isometric particles can form thixotropic structures due to electrostatic interactions.