Fluid substance, for the most part colourless, used to protect the surface, on which it is applied in thin layers, thanks to its properties of flexibility, strength, permeability, and adherence. In general varnishes are made through the combination of substances of vegetable or animal origin and of a solvent, with the possible addition of small quantities of substances of mineral or vegetable origin with siccative, plasticising, or colouring functions. Other than as final protectives, varnishes may be used in painting (enriching the binders of the pigments or carrying out siccative functions) and for re-touching (assuring the adherence of the successive layers of the painting on preceding dry parts). Regarding the use of varnishes as a finish, the antique treatises, other than documenting the extreme variety of recipes, underline the fundamental aesthetic role of varnishes. See also resins.