Lithographs in the catalogue.

Lithography works on the principle that grease and water repel one another. An artist draws directly onto stone or a metal plate with a greasy crayon or ink, and when the surface is dampened and inked, colour clings only to the drawn marks.

The technique preserves the immediacy of an artist’s hand — soft gradations, sketch-like line, and painterly tone — which is why it became a favoured medium for Picasso, Chagall, Miró, and later Hockney. Collectors prize lithographs for this closeness to the original drawing.