Salted paper or simply salt prints share their roots with two other silver nitrate processes, albumen and calotype. Salted paper and albumen are pop or printing-out processes, where the image becomes fully visible during exposure, requiring no developer in the darkroom, just a fixer to make it stable. It generally has two characteristics: exposures are long and it is "self-masking". There is a visual crossover between the two processes when some salted paper formulas call for a portion of egg white in the salting step to give gloss and depth and some albumen paper formulas call for a portion of starch in the egg white salting step to make the surface appear matte. The calotype process could be used to make a print but these were very rare. After the public announcement of photography in 1839, William Henry Fox Talbot continued to experiment with this in-camera paper negative.