A distinction is essentially made between four processes: gravure, letterpress printing, flat screen printing (offset printing) and silkscreen printing (serigraph).
Gravure – the printing parts are deeper than the non-printing parts: the image being printed is engraved, lasered or etched in the form of cells in the printing form ( electromechanical gravure, laser gravure, laser etching). The printing ink is input into the cell by partially dipping the printing form into the ink bath. Before transfer to the substrate, the surface (non-printing surface) is wiped clean of ink again with a doctor blade. The ink that remains in the cell in this way is then transferred to the substrate.
Letterpress printing – the printing parties are higher than the non-printing sections: all of the non-printing sections have to be removed during the manufacture of the printing form. The printing ink ultimately adheres to the embossed surfaces, through which the ink is transferred to the printing substrate. The still relatively new flexo printing process (mid 19th century) works according to this principle.
Flat screen printing – the printing and non-printing surfaces lie on a level: the process uses the separating effect of water and fat. The motif is applied to the printing form in such a way that ink-friendly sections (lipophile sections) are created, whereas the non-printing sections behave in a water-friendly way (hydrophile). In the printing process, the printing form is initially wet with a water film, and then the printing plate is coloured with ink. Thanks to its characteristics the printing ink only adheres to the lipophile sections and is transferred from there to the printing substrate. The best known flat screen printing process is offset printing. Here the transfer of the ink from the printing form first takes place to a rubber blanket printing cylinder and from there to the substrate.
Silkscreen printing – the printing form acts as a template. A fine-meshed fabric is stretched on a frame. The non-printing areas are non-permeable, while the fabric is open in the printing areas. The ink is then printed with the help of a doctor blade through the fabric onto the printing substrate. Silkscreen printing is a permeable printing process with a multitude of application possibilities.