SALTED PAPER PRINT
The successors to photogenic drawings, salted paper prints were introduced in 1839 by William Henry Fox Talbot. They were the first positive prints obtained from paper negatives, called calotypes, which is why they are sometimes erroneously called "positive calotypes."
Preparing the paper for these prints requires two steps: salting and sensitizing. A sheet of cotton paper free from impurities is first salted by being dipped in a solution of sodium chloride (sea salt) and dried. It is then placed in a mixture of water and silver nitrate, which reacts with the sodium chloride to produce light-sensitive silver chloride. This floating technique for the sensitizing stage is a definite improvement contributed by Louis-Désiré Blanquart-Évrard: it is more effective at coating the paper than the paintbrush application used in Talbot's procedure, resulting in a clearer image. After it is dried, the coated sheet can be used for daylight printing: the sensitized sheet is exposed to light in contact with a paper negative on a printing-frame. The light causes the silver chloride to break down into orange-brown metallic silver. The image has a matte appearance in naturally warm shades.
Once the image has been formed, it is fixed in a solution of sodium thiosulfate, which dissolves the residual sensitized salts, then washed. Toning, generally with gold, may be performed as an intermediate step to alter the tone of the image – with cooler tones ranging from warm brown to black-brown, black or sepia depending on the recipe – and improve stability.
Salted paper was immensely successful in Europe, particularly in France, from the 1840s to the 1860s. From 1850, binders began to be added to the salting bath to improve contrast and definition in the image and obtain a wider range of tones. The most commonly added substances – gelatin, albumen, and starch – lent their names to these variants, which gradually eclipsed the "ordinary" plain salted paper process to be replaced with albumen salted paper prints, gelatin salted paper prints, and starch salted paper prints.
Visual glossary of photographic techniques
© ARCP / Mairie de Paris, 2014