Guild procession of lithographers in Strasbourg, France, 28th June, 1840

Guild procession of lithographers in Strasbourg, France, 28th June, 1840. 'Cortege Industriel de Strasbourg', ('Strasbourg Industrial Procession'). Guild procession of lithographers with French flags. Lithography, discovered in 1796 by Alois Senefelder (1771-1834), whose bust is carried by the workers. The technique 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 press, inked, paper laid on it, and the wheel turned to draw it under a bar which presses down to make the print. ©SSPL/Science Museum