Lithography involves the printing of an image from a flat surface.
The technique, which was invented in the late eighteenth century,
relies on the principle that oil and water repel each other.
Traditionally employing a limestone slab that has been roughened
or smoothed according to the effects desired, the lithographer draws
directly on the surface with a greasy crayon or with a brush and
a liquid ink called tusche. Drawings for lithographs can also be made on specially treated zinc or aluminum plates (hence zincography and algraphy).