Printmaking - Lithography
Planographic printing (printing from a flat surface)
The technique used for producing a lithograph is called Planographic and was invented in 1978 in Germany by Alois Senefelder.
Planographic printing means printing from a flat surface,
which means that the printing and non-printing areas of the plate are all at the same level and is neither built up
(as with relief printing) nor cut into (as with intaglio printing).
The principle of the process is based on the property that water and oil does not mix
and is therefore creating both image and non-image producing areas.
The images is first drawn or painted with water-repellent materials (a greasy ink called tusche or lithographic crayons)
directly onto a polished piece of limestone or metal (zinc or aluminium) plate.
The stone or plate must then be chemically treated to prepare the image for printing.
The surface is first powdered with talc and then a solution of gum arabic and nitric acid (the etch) is applied.
This solution causes the areas covered by the image to attract the printing ink while the unmarked areas repel it.
The original drawing or painting is then wiped with a solvent which dissolves most of the image and leaving
it barely visible on the stone, but will retain the ink or pigment.
The entire stone or metal plate is then moistened with water (using a sponge)
which is absorbed by the unmarked areas and repelled wherever there is grease.
The surface must be kept wet to prevent the ink from adhering to non-image areas.
A large roller is inked with an oily ink is then rolled onto the surface of the plate.
The ink will adhere to the greasy areas, but is repelled by the wet parts of the stone or plate.
The finished inked plate is run through a lithographic press with a sheet of dampened paper placed on top.
The ink from the greasy areas is transferred onto the paper and producing a duplicate of the original painting or drawing.
For multi coloured prints, a separate stone or plate must be used for each colour.
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