Lithography is a planographic printmaking process, meaning that both the printing and non-printing areas are on the same flat surface. Unlike with intaglio and relief processes, the printing area is created by building layers of material on top of the surface, rather than working into it. Traditionally, the surface used in lithography is a piece of limestone, however thin mylar plates can also be used. The chemistry of lithography activates the repellent relationship between water and oil, so that ink will attract to the greasy printing areas and be rejected by the ‘clean’ non-printing areas.
Lithographic images are created using oil-based materials which leave greasy residue on the surface of the stone or plate. Some traditional materials for lithography include crayons and tusche, but any water resistant material can be used, including permanent markers or toner. Lithography crayons come in a range of grades, allowing you to build tone in a similar way to graphite pencils. Tusche is a greasy material that is dissolved in water to create washes which can be painted onto the surface, functioning in a similar way to watercolour paints.
Once your image has been created, it is then ‘etched’ into the stone or plate using a mix of acid and gum acacia. Nitric acid is traditionally used to process lithographic images, but tannic acid is a non-toxic alternative used at UNSW Art & Design. The ‘etch’ process binds the drawing materials together and locks the grease residue into the surface of the stone or plate so that when the surface is wet with water, ink will only attract to the drawn areas.
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