Modern inks are of two types: liquid inks and paste inks. All inks are made of three kinds of substances: vehicle, driers, and a pigment. The fluid part of the ink comprises the vehicle. It carries pigment on to the substrate. The type of vehicle chosen for a specific ink is dependent on the drying system to be utilized. The inks which dry through absorption use non-drying oil vehicles. The latter keeps "wet" until they get absorbed by the paper. The inks which dry through polymerization or oxidation need paper of certain qualities and drying oil vehicles which do not permit the draining of vehicle prior to oxidation. The inks which dry through evaporation use solvent resin vehicles having low boiling points. The inks which dry through precipitation need a glycol vehicle which is also water soluble. The water-insoluble resins are dissolved inside it. It means when water gets added to the vehicle glycol gets dissolved. The resin containing pigment does not, and precipitates out to the paper surface. These kinds of inks are termed moisture-set inks.
Inks which utilize a combo of various drying mechanisms, like quick-set inks, have the solvent part of the vehicle first to get absorbed into the paper. A mixture of resin-oil is left behind. This dries by polymerization and oxidation. The Quick-set inks use resin oil vehicle. The inks named cold-set inks utilize resin-wax vehicle, a solid when at room temperature, gets melted by heated rollers on the press and then applied to paper. It dries and reverts back to a solid. There are also niche products like water-soluble gum vehicles and photo-reactive vehicles. The latter "set" when exposed to multiple kinds of radiation.
The pigment is a component of ink which provides gloss, texture, and a number of other desirable characteristics to the printed image. The pigments could be white pigments, black pigments, and color pigments. These are produced either from mineral sources or from coal tar's organic derivatives. A number of specialty inks use materials like metallic powders. The additives of printing inks include driers, whose function is to speed up the ink drying function. Bodying agents increase the ink's viscosity. Waxes like paraffin and polyethylene are utilized to prevent printing defects like blocking and ink set-off. It also increases the scuff resistance of the ink. Teflon and other materials are added to "shorten" any ink. The ink tack can also be decreased by the addition of multiple compounds.