Offset printing inks are classified in different ways. Classification by substrate: According to the chemical name of the substrate, it can be divided into: polyethylene and polypropylene (nonpolar) inks. Pvc, polystyrene, ABS polycarbonate (polar) ink. According to the shape of substrate, it can be divided into soft plastic ink and hard plastic ink. According to the classification of printing machinery, it can be divided into sheet-fed offset printing ink and rotary offset printing ink; Selection of offset printing ink for different printing machines and different substrates. Ink used in web offset press The ink used in web offset press is usually called offset rotary ink. This kind of ink is based on the following two types: infiltration and exudation drying type: because of the high printing speed and fast ink drying speed of web offset press using newsprint and offset paper, most commonly used inks are infiltration and exudation drying type. Thermosetting ink: In modern trade web offset press, a drying device is added to the second half of the printing device. In order to adapt to this production, thermosetting ink is used. This kind of ink is heated in a drying device, and the solvent in the ink volatilizes, so that the ink film can be dried quickly. The content of drying oil (such as linseed oil) in thermosetting ink is less. However, the content of petroleum agent is more, and other components are slightly the same as those of sheet-fed offset printing ink, so the quality of paper used for thermosetting ink is better than that used for osmotic drying ink.