Heliography, sun writing, is the name given to the asphalt system of imaging invented by Joseph-Nicéphore Niépce in 1822. Interested in the new lithographic printing process, Niépce was seeking a simplifi ed way to print multiple impressions from a single master. He knew that bitumen of Judea asphaltum used as a resist in engraving, hardened after exposure to light. He coated a variety of materials and contact printed engravings on paper that he had oiled to enhance its translucency. After washing in several different solvents, the asphalt that was in contact with the inked lines of the engraving was washed away exposing the support below.
Niépce used glass, zinc, copper, lithographic stone, pewter, and silver-surfaced copper plates. In 1826, he succeeded in making what is now generally accepted to be the first permanent, camera-made image. He took one of his plates and placed it in a camera that he pointed out a second story window of his estate, Le Gras, near Chalon-sur-Saône in central France. The plate required at least one day exposure to record an image. After removing the unexposed areas of the asphaltum with a solvent, a direct positive image was visible against the polished background of the plate.