Photogravure

INTRODUCTION.Arout the year 1820 Niccphore Niepce made the discovery that bitumen, under certain conditions, was sensitive to light. He dissolved it in oil of lavender, and spread a thin layer of the solution thus obtained upon stone. This he exposed under a drawing- {making the paper transparent by waxing), and after sufficient exposure, oil of lavender was poured on. Those portions of the bitumen which had been exposed to the action of the light had become insoluble, and so remained while the lines which had been protected by the drawing were dissolved away. By treating the stone with an acid these lines were bitten or eroded, and could be printed from. Niepce afterward employed metal plates instead of the stone.Here we have the foundation for a number of printing processes of the present day, including photogravure.For many years, however, progress in processes for intaglio printing was very slow. In 1852 Talbot introduced a process termed photoglyphy, and in 1854 Paul PretschTable