lithography, (meaning ‘ writing with stone’), prints are pulled from a flat surface of limestone (also called a plano-graphic print process) treated to accept or reject ink, based on the principle that oil and water repel each other.
The surface of either a limestone block or metal (zinc or aluminium) plate is treated with gum arabic which is receptive to water after the image is drawn or painted with a grease-based medium. The dry drawing is processed and then, after wetting the stone, a greasy oil-based ink is rolled onto the surface which does not stick where there is water but repelled by the effects of the gum and moisture but adheres to the greasy design from which it can be transferred to paper when passed through a press. Painterly effects can be achieved, with subtle nuances of tone, fluidity and variability of line, and layers of colour. This form of printmaking is particularly suitable for people who enjoy drawing and watercolour techniques, as it prints exactly the marks you make although it is not necessary to be an experienced artist and anyone can enjoy the process. It is important to follow the method to the letter in order to chemically fix the image on the plate as there is nothing cut, bitten or stencilled; the image is thereby chemical magic. However, the result justifies the effort. A traditional limestone block might be too heavy to use for some people but equally good results can be achieved with the lighter metal plates.
Offset lithography is a modern development where the design is transferred from a stone/plate or a photo-litho plate onto a blanket (smooth rubber mat) which holds the ink and then deposits it onto the paper. This produces a positive image of the original design, unlike the direct presses used traditionally, which reverse the image.
Download PDF notes about Lithography