The alkyd resins belong to the family of thermosetting polyesters, organic macromolecules obtained through the reaction between an acid or an anhydride, an alcohol and a fatty acid or an oil. The oil content of the final product can be extremely variable (from 30 to more than 70% of the total volume of the resin) and it greatly influences the physico-chemical properties. The polymer structure of the alkyd resins makes them particularly suitable to be used as a basis for enamels and paints with different specific characteristics. The molecules of the structure, in particular, create strong structural interactions involving the formation of films able to cover any type of surface by protecting against aging, weather and wear. Historically, the paints based on alkyd resins have been among the first to be used in the field of the construction industry and, still today, they represent a preferred choice for the treatment of various materials, both for exterior and interior.