What is Lithography?
Lithography is a method of printing from a stone or smooth-surfaced metal plate that dates back to ancient times. Lithography can be used to print text as well as art onto paper and other materials. The hydrophobic (water-repelling) portion of the image serves as the “positive” while the hydrophilic (water-retaining) portion serves as the “negative.” Upon contact with a compatible printing ink and water formula, the ink adheres to the positive section of the image and the water clings to the negative, thus allowing a much better outcome than older physical printing methods such as intaglio or letterpress printing.
This method dates back to 1796 and was created by German author Alois Senefelder. It was founded on the principle that water does not mix with oil. Senefold originally developed this printing procedure as a cheap alternative for publishing theatrical works. In years past, artists or writers would draw or write on a lithographic limestone plate using oil, fat or wax. The stone was then treated with acid and gum Arabic, which would etch the areas of limestone left untouched by the drawing or writing. The etched areas would then begin to retain water and the artist would cover the area in oil-based ink. The ink was subsequently repelled by the water and was forced onto the surface of the original drawing. At the end of the process, the oil-based ink was transferred onto paper or another material.
Process of Modern Lithography
Though some fine art printmaking applications continue to practice lithography by its original method, most artists now use a more modern technique. In this updated procedure, a polymer-coated image is placed atop an aluminum plate where it can be printed directly from the plate or offset by transferring the image onto another medium, such as rubber, before publication. Offset lithography utilizes modern printing plates and are covered in a photosensitive emulsion. The “negative” image is placed into the emulsion atop the plate, which is then exposed to ultraviolet light. The image is allowed to develop, which creates a “positive” image. Modern offset lithography is used to create nearly all smooth, mass-produced items containing print and graphics such as books, newspapers, maps and posters.