Photographic Printing Processes: A Comparison and Chronology

The image now shown was a negative toned deep brown or black, with space that was exposed to light appearing dark, and space where light was prevented from reaching appearing lighter. It could be retouched with pencil or ink, and, if desired, waxed to make it more transparent, producing an image with more contrast to be produced after printing (Reilly, 1980). To make the salt print, the paper was soaked in a solution of salt and dried, and a solution of silver nitrate was brushed onto one side. When dry, it was placed on a calotype negative and under clear glass, then exposed to bright light (often the sun). After about fifteen minutes, a positive image appeared on the print paper. It was fixed using hypo (sodium thiosulphate, a solution suggested by Herschel that resulted in more stable prints and lacked the light purple highlights characteristic of saline fixation), then washed and dried. The two negative processes when used together created a positive image that was brownish red in hue (ibid).

The final image could only be as large as the negative it was printed from, as the print was produced through contact, so a large, cumbersome negative was needed for a larger print. In contrast to the daguerreotype, which had a coldly scientific crispness, the fibre and texture of paper prints produced a grainy, faintly speckled image. Although many people appreciated the artistic effect of this result, if desired it could be alleviated somewhat by using a glass negative rather than a paper negative (Gustavson, 500 Cameras: 170 Yeras of Photographic Innovation, 2011). The advantages of the calotype were many. The original exposure resulting in the negatives could be produced in minutes, much less time than it took to expose most daguerreo...

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