Lithography

The invention of lithography is credited to Alois Senefelder in 1796.
Right from the beginning, this technique had a considerable success in France; in fact, in 1831 there were already 59 printing workshops.
In 1840 the stone printing plate was replaced with ground zinc surface.

The principle of lithography – a special type of stone, with no internal imperfections, is honed. This stone has a special feature consisting in withholding a film of water (called countergraphism) in the undrawn parts, while the parts drawn with greasy ink (graphism) repel the water.
The ink spread with a roller onto the drawn and moist stone is withheld only in the greasy parts, while it is repelled in the white parts. Lithography procedure is based on incompatibility between ink and water.

Stone preparation and printing procedure – the stone to be used, consisting of calcium carbonate, must be compact and even.

The surface is to be honed with pumice stone and ground with river sand or carborundum.

A lithographic pencil or lithographic ink, both composed of greasy substances, is used to draw on the matrix. It is important to remember that the subject must be drawn as a mirror-image.

Once the artist's job is completed, a brush is used to spread a liquid composed of: nitric acid, gum Arabic and water. The nitric acid transforms all the parts that are not protected from the lithographic pencil or ink, from calcium carbonate into calcium nitrate, a hydrophilic substance.

Printing occurs through a lithographic press and the matrix is dampened every time with water and then ink is applied with a roller. The ink adheres to the drawing and is repelled by the dampened stone. Paper is placed on top and is printed.

There are other systems to transfer the grease of the drawing onto the stone or the plate, such as transfer paper, but the principle and the method are the same.