'McGahey's Lithography', c 1850.
© Science Museum / Science & Society Picture Library
Lithographed specimen drawn and engraved on stone by John McGahey and promoting his 'Lithographic Establishment' in Liverpool, showing decorative detailed scenes and examples of trade cards, charts, architects plans and a beam engine. Lithography, discovered in 1796 by Alois Senefelder (1771-1834), relies on the repulsion of oil and water to print from a flat surface, originally Bavarian limestone. A greasy crayon is used to sketch on the stone, which is then sponged with gum solution. The gum is repelled by the grease, making the undrawn areas ink-repellent. The stone is placed on the pres, inked, paper laid on it, and the wheel turned to draw it under a bar which preses down to make the print.