‘Christ Carrying his Cross’, made by Joseph Nicéphore Niépce in France, c. 1827.
This heliograph on a pewter plate is taken from a varnished engraving (whereabouts unknown).
Niépce made the first photograph on a pewter plate in 1826 or 1827. He named his process Heliography.
The Heliographic process used Bitumen of Judea, here on pewter, which hardens when exposed to light. To create a negative, an engraving was varnished, placed over the plate and exposed to sunlight. The soluble unexposed bitumen was dissolved in an oil of lavender-kerosene mixture and the plate was etched in an acid bath. The exposed hardened bitumen acted as a resist, so that the acid etched only areas of unexposed metal. The resulting heliographic plate was used to make final prints on paper.
The Heliographic process varies depending on how long the plate is immersed in acid. This plate is very lightly etched, the etching lines are so shallow that the plate could not be inked and printed.