Art from Stone: What is Lithography?

The very name of the technique gives us clues about the procedure: in ancient Greek, líthos = stone and gráphein = to write.

Invented at the end of the 18th century by Alois Senefelder, this printing technique uses stone as a matrix and is based on the principle of repulsion between grease and water. The drawing is made on a limestone using lithographic ink or crayon, both of which are greasy.

Then, an acidified gum arabic solution is used to cover the entire surface. The parts protected by the grease remain smooth, while the exposed parts are attacked by the acid and acquire a porous texture.

The matrix is cleaned and taken to the lithographic press, where it is moistened and a greasy ink is applied with the help of a roller. The porous areas that absorbed the water repel the ink, which is retained only on the smooth areas of the stone, defining the image to be printed.

In this case, two matrices are used, which are inked with different colors. In the 19th century the use of black and sepia was very common, which provided more visual resources. The matrices are printed on the same paper, leaving overlapping images.

For color prints, one stone must be used for each color. In this case, a complex breakdown of the original image becomes necessary, resulting in layers of printing colors. Each layer is applied to the print with a different stone.

Lithography was revolutionary because it allowed painters and designers to work directly on stone, eliminating the need to carve the matrix. This greatly facilitated the process, speeding up production compared to woodcuts and copperplate engraving.