The salt print was the dominant paper-based photographic process for producing positive prints during the period from 1839 through approximately 1860.
The salted paper print was the first type of paper print used in photography, and remained the most popular paper print until the introduction of the albumen print process in the 1850s. The salted paper technique was created by British photographer William Henry Fox Talbot. He called his negative process calotype printing, while the salt print process was used for making positive prints from the Calotype negatives. They both employ a technique of coating sheets of paper with silver salts, but the Calotype process differs slightly in chemicals used in the sensitization procedure, and uses an extra 'accelerator' step, immediately prior to exposure of the sensitized paper.[1][2]
Salt prints could be made from both paper and glass negatives. Paper negatives produced a grainy and slightly mottled image. Glass negatives produced a sharp, crisp image. Salt prints have white highlights.
Taylor, Roger. Impressed by Light: British Photographs from Paper Negatives, 1840-1860 (NY, Metropolitan Museum of Art, 2007)