Working in London, the painter Jacob Christoph le Blon secured a patent from George I for a process which he called "printing paintings."
To prepare each of his three printing plates, Le Blon used the technique of mezzotint engraving: a copper sheet is uniformly roughened with the finely serrated edge of a burring tool, and local regions are then polished, to varying degrees, in order to control the amount of ink that they are to hold.
To develop his process Le Blon needed to find three colored inks of suitable transparency, and to analyze the color that was to be reproduced into its components. Sometimes he used a fourth plate, carrying black ink. This technique allowed the use of thinner layers of colored ink, reducing cost, and accelerating drying.
