William Henry Fox Talbot’s original salted silver nitrate paper evolved between 1834 and 1839.
Talbot used smooth writing paper washed in a weak solution of common salt, dried, then coated with a solution of silver nitrate, resulting in light-sensitive silver chloride. Once dry, the paper could be printed out in strong sunlight.
The resulting image of metallic silver was fixed in a strong solution of salt.
Talbot refined the process, and Sir John Herschel suggested sodium thiosulphate (hypo) as a fixing agent. Salted paper was the basis for Talbot’s Calotype process, which used silver nitrate and gallic acid to develop up a latent image in the exposed paper, and is the foundation of modern silver-based photography.