- L. J. Schaaf
(b Chalon-sur-Saône, March 7, 1765; d Gras, nr Chalon-sur-Saône, July 5, 1833).
French inventor. Niépce and his brother Claude (1763–1828) were little-known scientists who developed a functioning internal combustion engine and a sugar extraction process, both of which were commercial failures. Their fortune became depleted by a lifetime of experimenting. Harmant (1980) has suggested that their photographic experiments originated in the late 18th century; certainly Nicéphore had used nitric acid to fix the images of the camera obscura on silver chloride paper by 1816. Although no known examples survive, this was an advance on the methods of Thomas Wedgwood, who was unable to preserve his images.
Heliography was invented by Nicéphore Niépce in 1824. The discovery probably stemmed from his interest in printmaking, which led him to seek to capture natural images on lithographic stone. Heliography used the light sensitivity of bitumen, dissolved in a solvent and coated on to a glass, metal, or stone plate. Prolonged exposure to sunlight in a camera (or under a waxed engraving) selectively hardened the bitumen, and subsequent washing with solvent removed the unexposed (and therefore unhardened) areas. The remaining bitumen formed a visible image that could be employed as a resist in etching or lithographic printing....