DIFFERENCES IN IMAGE TONALITY PRODUCED BY DIFFERENT TONING PROTOCOLS FOR MATTE COLLODION PHOTOGRAPHS
8 PROS AND CONS OF COLLODION PAPER
Although it was almost impossible to identify a collodion from a gelatin print once it was mounted and presented to the patrons, some difference existed in the processing. For example, gelatin paper was not as well suited for producing the wide range of tones readily obtained with collodion paper. In June 1897, Wilson's Photographic Journal recommended the use of collodion paper to its readers because it possessed many advantages over gelatin:
Like albumen, [collodio-chloride paper] does not require a special type of negative. It may be toned in almost any bath. Any color, from red brown to a deep rich purple black, or even a cold black, can be obtained at will…. The prints can be blotted off and dried before the fire without risk of injury (quoted in Welling 1978, 380).
During the summer or in warm regions, collodion paper was preferred over gelatin because its emulsion did not swell and was more resistant to water. Gelatin paper also had to be washed longer than collodion paper because the various processing solutions penetrated more thoroughly in the swelled emulsion.
Collodion paper did have the disadvantage of curling in the baths. To avoid this problem, photographers would sometimes coat the back of the paper with an alcoholic varnish or with plain collodion, but this method was considered too costly for commercial practice. An alternative was to lay the prints face down in a tray filled with warm water and let them sit there for about 10 minutes, while gently patting them (Woodbury  1979, 115). Collodion prints were also more susceptible to chemical impurities such as sodium thiosulfate (fixer) residue in the blotters in which they were left to dry and to finger prints (Photo-Miniature 1910).