Editing Lithography (section)

===Modern lithographic process===
{{main|Offset printing}}
[[File:Gubernie zachodnie krolestwo polskie 1902.jpg|thumb|1902 Polish lithograph map of the western parts of the [[Russian Empire]]. Original size {{convert|33|×|24|cm|in|abbr=on}}.]]

High-volume lithography is used to produce posters, maps, books, newspapers, and packaging—just about any smooth, mass-produced item with print and graphics on it. Most books, indeed all types of high-volume text, are printed using offset lithography.<ref name=":0">{{Cite web |last=Meyer |first=Isabella |date=2022-06-16 |title=Lithography - Understanding the Art of Lithography Printmaking |url=https://artincontext.org/lithography/ |access-date=2025-03-19 |website=Art in Context |language=en-US}}</ref>

For offset lithography, which depends on photographic processes, flexible [[Aluminium|aluminum]], [[polyester]], [[BoPET|mylar]] or paper printing plates are used instead of stone tablets. Modern printing plates have a brushed or roughened texture and are covered with a photosensitive [[emulsion]].  A [[Negative (photography)|photographic negative]] of the desired image is placed in contact with the emulsion and the plate is exposed to [[Ultraviolet|ultraviolet light]]. After development, the emulsion shows a reverse of the negative image, which is thus a duplicate of the original (positive) image. The image on the plate emulsion can also be created by direct laser imaging in a CTP ([[Computer to plate|computer-to-plate]]) device known as a platesetter. The positive image is the emulsion that remains after imaging. Non-image portions of the emulsion have traditionally been removed by a chemical process, though in recent times, plates have become available that do not require such processing.<ref name=":0" />

[[File:Lithography press with map of Moosburg 02.jpg|thumb|left|upright|Lithography press for printing maps in Munich.]]
[[File:Lithography machine in Bibliotheca Alexandrina.jpg|thumb|right|Lithography machine in [[Bibliotheca Alexandrina]].]]
The plate is affixed to a cylinder on a printing press. Dampening rollers apply water, which covers the blank portions of the plate but is repelled by the emulsion of the image area. Hydrophobic ink, which is repelled by the water and only adheres to the emulsion of the image area, is then applied by the inking rollers.

If this image were transferred directly to paper, it would create a mirror-type image and the paper would become too wet. Instead, the plate rolls against a cylinder covered with a rubber ''blanket'', which squeezes away the water, picks up the ink and transfers it to the paper with uniform pressure. The paper passes between the blanket cylinder and a counter-pressure or impression cylinder and the image is transferred to the paper. Because the image is first transferred, or ''offset'' to the rubber blanket cylinder, this reproduction method is known as ''offset lithography'' or ''[[offset printing]]''.<ref>see diagram at [http://www.compassrose.com/static/Offset.jpg compassrose.com]</ref>

Many innovations and technical refinements have been made in printing processes and presses over the years, including the development of [[Printing press|presses]] with multiple units (each containing one printing plate) that can print multi-color images in one pass on both sides of the sheet, and presses that accommodate continuous rolls (''webs'') of paper, known as web presses. Another innovation was the continuous dampening system first introduced by Dahlgren, instead of the old method (conventional dampening) which is still used on older presses, using rollers covered with molleton (cloth) that absorbs the water. This increased control of the water flow to the plate and allowed for better ink and water balance. Recent dampening systems include a "delta effect or vario", which slows the roller in contact with the plate, thus creating a sweeping movement over the ink image to clean impurities known as "hickies".

[[File:Litography archive of the Bayerisches Vermessungsamt.jpg|thumb|Archive of lithographic stones in Munich.]]

This press is also called an ink pyramid because the ink is transferred through several layers of rollers with different purposes. Fast lithographic 'web' printing presses are commonly used in newspaper production.

The advent of [[desktop publishing]] made it possible for type and images to be modified easily on personal computers for eventual printing by desktop or commercial presses. The development of digital [[imagesetter]]s enabled print shops to produce negatives for platemaking directly from digital input, skipping the intermediate step of photographing an actual page layout. The development of the digital [[platesetter]] during the late 20th century eliminated film negatives altogether by exposing printing plates directly from digital input, a process known as computer-to-plate printing.