July 1, 2022
Lithography (from the ancient Greek λίθος, lithos, 'stone', and γράφειν, graphein, 'to write') is a printing procedure that consists of tracing a drawing , a text, or a photograph, on a calcareous stone or a metal plate. Today it is almost in disuse, except for obtaining and duplicating artistic works. Its creator was the German playwright, actor, and typesetter Aloys Senefelder in 1796 and was initially used mainly for musical scores and maps. It is a printing method originally based on the immiscibility of oil and water . The impression is made from a stone (lithographic limestone) or a metal plate with a smooth surface. Lithography can be used to print text or images on paper or other suitable material. Originally, the image to be printed was drawn with a greasy substance, such as oil, grease, or wax, on the surface of a flat, smooth limestone plate. The stone was then treated with a mixture of weak acid and gum arabic ("etching") which made the parts of the stone's surface that were not protected by grease more hydrophilic (i.e. attracted water). ). For printing, the stone was first moistened. The water only clung to the rubber-treated parts, making them even more oil-repellant. An oil-based ink was then applied, which only adhered to the original drawing. The ink was finally transferred to a blank sheet of paper, producing a printed page. This traditional technique is still used for artistic stamping. In modern commercial lithography, the image is transferred or created as a patterned polymer coating that is applied to a flexible plastic or metal plate. Printing plates, whether stone or metal, can created using a photographic process, a method that may be called "photolithography" (although the term often refers to a vaguely similar microelectronics manufacturing process). Offset printing or "offset lithography" is a production of lithography in which ink is transferred from the plate to the paper by means of a rubber plate or cylinder, rather than by direct contact between the two. This technique keeps the paper dry and allows fully automated high-speed operation. It has largely replaced traditional lithography in medium- and high-volume printing: since the 1960s, most books and magazines, especially those illustrated in color, have been printed with offset lithography from photographically created metal plates. . As a printing technology, lithography is different from engraving, in which a plate is engraved, etched, or halftone engraved to mark cavities containing the printing ink, as well as from woodcut or printing. typographic, in which ink is applied to the raised surfaces of letters or images.