Types of printing
_Printing is described as the process of transferring ink onto paper (or another substrate) via a printing plate.
Many different printing technologies have been developed and these can be divided into four main technologies according to the type of image carrier used.
Letterpress (Relief) Printing - Here, the printing elements (letters, lines, dots, etc.) are raised. When the printing plate is inked, the ink adheres to the raised (printing) parts and is then transferred under pressure onto the printing substrate. The main examples of this printing technology are letterpress which, until a few decades ago, was the dominant printing technology and flexography which, by the middle of this century, had started to be used more and more in packaging printing.
Gravure Printing - Here, the printing elements are recessed. The gravure cylinder surface is covered with low viscosity ink (“flooded”) and then passed under a doctor blade which removes all the excessive ink, leaving ink only in the recesses. The printing material is pressed onto the cylinder surface and takes up the ink from the recesses.
Lithography - Here, printing and non-printing elements are at the same planographic level but are usually made from different materials (e.g., aluminum and polymer coating) with different chemical and physical surface properties. During printing, the non-printing elements are usually made ink-repellent first (by wetting) and the plate is then inked so that the ink is taken up only by the printing areas. The main example of lithography is offset printing, which is today the dominant printing technology. Offset printing is an indirect printing technology, that is, the ink is first transferred to an intermediate carrier (rubber blanket) and from there onto the substrate.
Screen Printing - Here, the printing plate consists of a fine mesh (e.g., nylon). The non-printing elements of the mesh are blocked by a coating (stencil). As with gravure printing, the screen plate is covered with ink and a squeegee (blade) is passed over it. Through the pressure of the squeegee the ink is pushed through the screen onto the substrate lying below.
Many different printing technologies have been developed and these can be divided into four main technologies according to the type of image carrier used.
Letterpress (Relief) Printing - Here, the printing elements (letters, lines, dots, etc.) are raised. When the printing plate is inked, the ink adheres to the raised (printing) parts and is then transferred under pressure onto the printing substrate. The main examples of this printing technology are letterpress which, until a few decades ago, was the dominant printing technology and flexography which, by the middle of this century, had started to be used more and more in packaging printing.
Gravure Printing - Here, the printing elements are recessed. The gravure cylinder surface is covered with low viscosity ink (“flooded”) and then passed under a doctor blade which removes all the excessive ink, leaving ink only in the recesses. The printing material is pressed onto the cylinder surface and takes up the ink from the recesses.
Lithography - Here, printing and non-printing elements are at the same planographic level but are usually made from different materials (e.g., aluminum and polymer coating) with different chemical and physical surface properties. During printing, the non-printing elements are usually made ink-repellent first (by wetting) and the plate is then inked so that the ink is taken up only by the printing areas. The main example of lithography is offset printing, which is today the dominant printing technology. Offset printing is an indirect printing technology, that is, the ink is first transferred to an intermediate carrier (rubber blanket) and from there onto the substrate.
Screen Printing - Here, the printing plate consists of a fine mesh (e.g., nylon). The non-printing elements of the mesh are blocked by a coating (stencil). As with gravure printing, the screen plate is covered with ink and a squeegee (blade) is passed over it. Through the pressure of the squeegee the ink is pushed through the screen onto the substrate lying below.