Printing inks are complicated mixtures of chemical compounds. The composition of printing inks varies by the printing process, by whether printing is sheet-fed or web-fed, and by the target substrate. The composition varies by the solvent base, be it oil or water. It varies by drying mechanism and by whether the drying is by primarily chemical, e.g., oxidation polymerization, ultraviolet cure, or physical processes, e.g., evaporation, absorption.