Lithography works on a chemical principle that grease and water repel each other. All work remains on the surface. There is no carving the artist marks the stone with a greasy crayon and then covers it with a tin film of water. When the ink is applied it is attracted only to the greasy image and is repelled by the water which fills the other areas of the stone.
Fine art printing:
Resurfacing a previously used Bavarian limestone in special graining sink the artists wets the stone and applies carborundum grit. The surface texture of the stone which will effects the look of the final print, depends upon the level of grit the artist chooses. The stone can have a course rough texture or a smooth glass like surface. By grinding with another stone the artist can be sure that the surface of the stone is levelled and ready for printing. If the surface isn’t perfectly levelled it will break under the intense pressure of the press.
In lithography the artist creates the image by marking the stone with greasy materials. He begins with a liquid substance called touche. He paints it on the stone to create the background of the image. To transfer an outline the artist copies the image on a tracing paper and dusts the front of the sheet with iron oxide. Since the printing process will reverse the image he places the tracing paper face down on the stone. As the artist retraces the design, the iron oxide is transferred to the stone.
To begin processing the stone the artist applies a layer of talc to absorb the access grease from the crayon and touche, next he brushes on powder rosin to protect the stone from the strength of the acid. To chemically fix or etch the image on to the stone, the artist mixes a solution of gum Arabic and a small amount of nitric acid. The acid fixes the greasy image areas into the stone and desensitized the non-image areas from receiving ink.
To prepare the stone for printing the artist dissolves the crayon and touche of the original drawing with an oil based solvent. With a leather roller he spreads a thick lithography ink on a flat surface of an inking slab. The water collects in the non-image areas of the stone and repels the greasy ink. While the image areas attracts the greasy ink and repels the water. A sheet of paper is then carefully placed on top of the stone and is then rolled through the press. Once the press is done the paper is removed and has a mirror image of the inked stone.
