Lithographic printing is a printing process that "works on the principle that grease and water repel each other." It acts as an "offset" printing technique because the ink is not applied directly to the printing plate (a stone in the case of lithography). This style of printmaking most often appears in text printing, However, an artist or any other lithographic printer can use several additional techniques to make her prints unique.
Stone Grinding
Different stone types can be ground to different textures to produce varying effects when used with lithographic printing. You can apply a carborundum grit to a wet stone and work it in using a special grinding tool. You can then use another stone to grind the stone to the desired texture. Textures can vary from rough to smooth, with each texture having an effect on the final print. This process also allows the artist to ensure the stone remains level and ready for the printing process.
Grease Application
The grease applied to the stone is one of the most crucial parts of the printing process. The artist can draw the image he wishes to print directly onto the printing stone or use an image transfer process that involves touche and iron oxide. Regardless of the process used, the image drawn on the printing stone with the grease crayon is the image that will be transferred to the printing material when the printing process is complete.
Image Etching
After the artist has drawn the image with the grease crayon, she then "etches" the image into the stone. During the etching process, the artist applies a layer of talc to absorb any excess grease, followed by a layer of rosin to protect the stone from the etching acid. The artist then applies a mixture of gum arabic and nitric acid to the stone to etch the image. The artist then removes the original image with a solvent, leaving only the etched image behind. Finally, the artist applies asphaltum to make the ghost image more receptive of the ink.
Ink Application
The artist spreads the lithography ink evenly on an inking slab with a leather roller. During this process, the ink collects on the roller. The artist then dampens the printing stone and rolls the roller across the printing stone to transfer the ink onto the stone.
Printing Process
Paper is placed on the printing stone along with newsprint and timpin to even the pressure applied by the press. Then, the artist lowers the press's pressure bar and rolls the printing stone through the printer. When the paper is peeled away from the stone, the image transfers from the stone onto the paper.
