The process of printing is the act of transferring an image to a substrate using a special photographic process. The image can be either an abstract or a photograph. The printing industry relies heavily on specialized photographic equipment and methods.
During the photographic process, the paper is either exposed to a negative or positive image. These images are then transferred onto the substrate either directly or indirectly. The paper is then passed through electrically charged pigmented toners to produce the desired effects on the final product.
There are five main types of printing processes. These are planographic, intaglio, screen, relief and offset lithography. The main difference between these processes is the type of image carrier used.
Intaglio is a type of printing that involves areas that are printed below the surface. The intaglio process also uses non-printing areas on the plane surface. In addition to being a three-dimensional impression, an intaglio is a print with printing areas on a plane surface. The type of intaglio varies depending on the type of paper used.
In the indirect process, an image is transferred to a photomechanical plate. The photomechanical plates are usually made of aluminum. These plates have good color reproduction and long life. However, they are more expensive.
Planographic, or lithography, is an indirect process that involves a sheet of paper that is placed in contact with the lithographic plate. This enables the ink to adhere to the paper surface. The image is then transferred to the plate via a graphic film.
The five major printing processes are all different in general. In addition to the type of image carrier, the other key differences are in the method of exposing the plate and the inks used. The cyan, yellow, black and red tonal values are the primary colors in a four-color process. In offset lithography, the tonal values are reversed. In the web press, a continuous reel feeds the paper. The sheets are then cut off at a cut-off point.
Relief prints involve an etched or engraved image that stands out from the background. In addition, the printing areas are recessed, so that as the paper passes through them, the image is formed. This technique is used in many kinds of printing, including letterpress and screen. The recessed area is a result of the wire mesh cylinder that imparts a surface texture to the paper.
Offset lithography is an indirect method of producing a high-quality, low-cost image. The plate is a thin piece of aluminium. It is generally thinner than a paper plate and lasts longer. Its optimum image quality is achieved when it is exposed directly or indirectly to a light-sensitive coating.
In addition to the four primary colors, other inks include alkali blue, toluidine red, titanium oxide and cyan. These inks are added to the colored inks to create intermediate shades. The inks are then blended, to create transparent inks that do not block the color inks.
The inks are then dried. The vehicle, or glue, controls the flow of the inks and the drying process. The vehicle also provides the adhesion of the pigments to the paper surface. This is especially important in the web press, where the paper is under pressure.