An inhibitor added to a lithographic or screen printing ink to retard oxidation of the ink vehicle and thereby prevent excessive or overly rapid ink drying. Antioxidant compounds most often used are oximes (such as methyl ethyl ketoxime), phenolic antioxidants (such as butylated hydroxy toluene), and quinones (such as hydroquinone), which are slightly, moderately, and highly effective, respectively. A class of antioxidants is called antiskinning agents. A chemical that slows the drying time by reducing the evaporation rate of the solvent is called a retarder.