Stone Lithography was invented in 1798 by Aloys Senefelder. The printing process is based on the principle that oil and water do not mix. The artist begins with a smooth block of limestone ("lithos" is Greek for stone). Stone from the Bavarian quarries where Senefelder developed the process is preferred because of it’s qualities. The artist begins by drawing an image on the stone with a greasy crayon, or with a strong liquid called "tusche". Tusche can be brushed on like ink or applied with a pen for different effects.
Lithography allows the artist to draw freely on the stone. After the artist has completed the drawing, the stone is chemically treated to fix the image securely. The grease in the lithographer's crayon or tusche will repel water during the printing process. The unmarked, grease-free surface of the stone will absorb water.
In the next step, the entire stone is cleaned with a solvent. The printmaker wets the stone prior to applying the ink. The portion of the stone's surface without image absorbs water and will repel the oil-based ink. The area marked with greasy crayon or tusche accepts and retains the ink when it is applied to the stone.
Here is an example of a finished poster.
The finished poster is at the top left. Only 3 Stones were used to make this final poster. No Black was used. The combinations of colors such as yellow, red and blue laying over each other make all the colors of the finished poster. A separate stone must be produced for each color, and the paper then carefully aligned for the multiple pressings required to match up the different colors on the same printed sheet.
The printer uses a lithographic press to force the paper against the ink. Since lithography stones do not wear out the process of wetting, inking and pressing the stone can be repeated many times. A stone is ground down when a new image is produced. Along with this capability of producing multiple impressions, lithography excels at creating areas of vivid, solid color as well as subtle shading effects.