In lithography, the printed and unprinted elements are on the same level. The subtlety of print zones is that they accept ink, where the unprintable areas of the plates are inks. This effect is created by physical, maxillary superficial phenomena.
Lithographic printing can be easily divided into:
- Stone lithography (direct printing technology using a printing form made of stone)
- collotype (direct printing method),
- offset printing (indirect printing) and
- di-lito (direct printing process with offset printing plate).
Lithograph was created by Alois Senefelder in 1796. The image to be printed was captured with stone using special ink. The stone was moistened shortly before it rose, after which the un-displayed fields of the stone surface did not become ink.
Collotype is another lithography technology. The light-sensitive level of gelatin is exposed on a glass base over a negative one and then develops. Places with different swelling properties with respect to water are produced. After the printing plate has been wetted, the distinctive color shade absorption characteristics are generated. Like stone lithography, the collotype is used only for art goods (and has very short runs).
Offset printing is a leading lithographic technology. This is an indirect lithographic technology, the situation when the ink is first transferred from the printing form to an adaptable support center - a blanket, and then to the substrate.
To obtain the effect of imprint on the plate (excellent interaction of the surface of the printing plate and ink), there are two widely used methods:
- Conventional offset printing technology: Moistening the printing plate using a wetting solution (water with additives). Moisturizing solution is applied to the plate in a very thin film using moisturizing rollers. The non-image fields of the plate are hydrophobic, that is, water-intake and ink-receiving surfaces are oleophilic and approximately 100% immune to water. Moisturizing film prevents ink transfer. Since this technology is, in fact, the most common, repellent revenue among inks and moisturizing solutions is regularly associated with offset printing. For this reason, "offset printing" requires coloring and moisturizing devices.
The technology of wasteless offset printing: the surface of the plate is mainly water-repellent, for example, due to the corresponding layer of silicone. The recharge ink base zone is intentionally interrupted by a layer of silicone (only about 2 microns thick). This treatment is known as "waterless displacement" (very often, as "dry displacement"). Both of these technologies require the use of suitable printing plates and special inks.
The di-lit technology, the lithographic technology, in which the printing plate is printed directly on the substrate, was created exclusively for newspaper printing. The advantage of this technology lies in the fact that you can use conventional rotary printing machines with pressing. The printing blocks of these presses have been modified by installing a wetting device. Printing was carried out using conventional printing plates, without special special coating, which was necessary to apply to them due to the very high voltage due to direct contact with the paper and high stability during the total circulation required for printing in newspapers. This technology has played a short-term role. When new investments were made in newspaper printing companies, this type of technology was replaced by offset printing presses, which were printed on a substrate using an offset cylinder.
The advantages of offset lithography
- consistently high image quality.
- much faster and much easier to make slabs.
- the increased service life of the plates, as they only come into contact with the printing blanket, which turns out to be softer and less abrasive than paper
- the most inexpensive production on high-quality images in large quantities.
disadvantages
- high cost for small quantities
- image quality is great for commercial purposes, but not as good as gravure or photogravure printing.
