The technique of lithography (from the Greek for "stone drawing") relies on "the principle of the antipathy of grease and water." Generally, the stone on which the image is initially created is limestone. The image is drawn on the stone with some greasy material. After the image is drawn, the stone is dampened and ink is applied with a roller. The greasy image repels the water and holds the oily ink while the rest of the stone's surface does the opposite. The stone is chemically treated after the image is created in order to enhance this effect. Some materials for drawing the image are litho crayons and pencils (containing wax, pigment, soap and shellac), liquid tusche (similar in composition to the crayons but water soluble), stick tusche (a solid form), conte crayons, pens and graphite pencils to name a few.
The finished stone is placed on a bed that carries it through the press. The paper is placed on top of the stone with some backing papers to protect it. A sheet of metal or plastic is placed on top of all the materials and they are braced together. A roller underneath that is turned by a handle moves the bed. This is similar to the intaglio press except that a scraper bar instead of a roller applies the pressure from above. The scraper bar slides along the greased metal plate pressing the paper against the stone so that it lifts the ink from where the greasy drawing material holds it on the stone.
Color lithography is a more complex process that usually involves multiple pressings, one for each color in the image. This requires an extensive knowledge of color theory because the process requires the mixing of colors on the final image itself. According to one book on lithography technique, "The original color drawing should be treated as a guide for the final print, not as a finished work to be duplicated exactly." Different stones are sometimes used for each color but the same stone can be used for multiple colors.
Because of the equipment used and the knowledge and skill required for the printing process, lithography lends itself to collaboration between an artist and a printer. Even pulling a proof of a large lithograph requires two people. A recent exhibit at a gallery focuses on collaboration as an important aspect of the production of prints. Working with a skilled printer the artist can know exactly how to achieve certain effects and how the print can benefit most from the chosen medium.
As a result of the variety of the materials that can be used and the versatility of the imagery that can be represented as the artist creates directly on the stone, lithography is an excellent medium for modern artistic expression.
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