Natural resins are organic substances generally of vegetable origin, with strong adhesive properties and also water-repellent, of various and complex chemical compositions and of extremely varying use. Known since ancient times, they are essentially used to obtain finishing and retouching varnishes (see varnish), and also stucco, adhesive mixtures, consolidant solutions, etc. In restoration, for having been in good part substituted by polymerized resins, they continue to be equally used. According to their origin and consistence, the natural resins are generally classified into oleo-resins, balsams, fossil resins and animal resins (this last resin in reality only includes shellac).