Editing Lithography (section)

===Lithography on limestone===
[[File:Litography negative stone and positive paper.jpg|thumb|Lithography stone and [[mirror image]] print of a map of Munich.]]

Lithography works because of the mutual [[Hydrophobe|repulsion of oil and water]]. The image is drawn on the surface of the print plate with a fat or oil-based medium (hydrophobic) such as a [[Crayon|wax crayon]], which may be pigmented to make the drawing visible. A wide range of oil-based media is available, but the durability of the image on the stone depends on the [[lipid]] content of the material being used, and its ability to withstand water and acid. After the drawing of the image, an [[aqueous solution]] of [[gum arabic]], weakly acidified with [[nitric acid]] ({{chem|HNO|3}}) is applied to the stone. The function of this solution is to create a hydrophilic layer of [[calcium nitrate]] salt, {{chem|Ca(NO|3|)|2}}, and gum arabic on all non-image surfaces.<ref name=EB1911/> The gum solution penetrates into the pores of the stone, completely surrounding the original image with a hydrophilic layer that will not accept the printing ink. Using lithographic [[turpentine]], the printer then removes any excess of the greasy drawing material, but a hydrophobic molecular film of it remains tightly bonded to the surface of the stone, rejecting the gum arabic and water, but ready to accept the oily ink.<ref>[[A. Hoen & Co.|A. B. Hoen]], Discussion of the Requisite Qualities of Lithographic Limestone, with Report on Tests of the Lithographic Stone of Mitchell County, Iowa, [https://books.google.com/books?id=XBIMAAAAYAAJ&lpg=RA1-PA339&pg=RA1-PA339 Iowa Geological Survey Annual Report, 1902], Des Moines, 1903; pages 339–352.</ref><ref>{{cite book |last1=Gascoigne |first1=Bamber |title=How to Identify Prints: a complete guide to manual and mechanical processes from woodcut to ink jet |date=1988 |publisher=Thames and Hudson |isbn=978-0500234549 |location=Spain |page=1c}}</ref>

When printing, the stone is kept wet with water. The water is naturally attracted to the layer of gum and salt created by the acid wash. [[Printing ink]] based on [[drying oil]]s such as [[linseed oil]] and [[varnish]] loaded with [[pigment]] is then rolled over the surface. The water repels the greasy ink but the hydrophobic areas left by the original drawing material accept it. When the hydrophobic image is loaded with ink, the stone and paper are run through a press that applies even pressure over the surface, transferring the ink to the paper and off the stone.<ref>{{Cite web |title=Lithograph |url=https://www.metmuseum.org/about-the-met/collection-areas/drawings-and-prints/materials-and-techniques/printmaking/lithograph |access-date=2025-03-19 |website=The Metropolitan Museum of Art |language=en}}</ref>

[[File:Luigi Verardi after Dominico Ferri - Gaetano Donizetti - Carrefour de St Jean et Paul. Dans l'Opéra Marino Faliero.jpg|thumb|This very early colour lithograph from 1835 uses large washes of orange and cyan with black ink providing the details.|left]]
Senefelder had experimented during the early 19th century with multicolor lithography; in his 1819 book, he predicted that the process would eventually be perfected and used to reproduce paintings.<ref name="meggspage146"/> Multi-color printing was introduced by a new process developed by [[Godefroy Engelmann]] (France) in 1837 known as [[chromolithography]].<ref name="meggspage146"/> A separate stone was used for each color, and a print went through the press separately for each stone. The main challenge was to keep the images aligned (''[[Printing registration|in register]]''). This method lent itself to images consisting of large areas of flat color, and resulted in the characteristic poster designs of this period.<ref name=":0" />

[[File:Lithographer at work, 1880.jpg|thumb|right|A lithographer at work, 1880.]]
"Lithography, or printing from soft stone, largely took the place of engraving in the production of English commercial maps after about 1852. It was a quick, cheap process and had been used to print British army maps during the [[Peninsular War]]. Most of the commercial maps of the second half of the 19th century were lithographed and unattractive, though accurate enough."<ref>Lynam, Edward. 1944. British Maps and Map Makers. London: W. Collins. Page 46.</ref>