SALTED PAPER PRINTING
This is a very simple process involving only the use of common salt and silver nitrate to form a light sensitive silver chloride emulsion which is very similar to commercial printing-out paper in tonality and emulsion speed. As with the Van Dyke and Kallitype emulsions this silver emulsion should be coated onto acid-free paper or cloth grounds if permanence and avoidance of stains is desired.
Salting: Paper or cloth is immersed in a solution 1 or 2 teaspoons of non-iodized salt (sea salt is best) and 1000 cc of distilled water until thoroughly saturated (3-5 minutes). Excess salt water should be drained or squeegeed off and the ground (paper/cloth) hung to dry; after a few minutes, when the drying has begun, the ground should be turned upside-down relative to its initial drying position, so that evenness of the saturation of the salt solution is maintained. When dry, salted paper can be stored under any light conditions indefinitely.
Sensitizing: The salted paper is sensitized by floating it upon, or brushing on, a solution of 25 grams silver nitrate and 250 cc distilled water. If the floating method is used, 10-15 seconds is satisfactory for the desired formation of the silver chloride. Float, do not submerge the salted paper unless you wish to sensitize both sides, as you will be wasting the expensive silver nitrate; the chemical reaction which forms silver chloride need only occur on the surface, not within the paper.
If you do sensitize by floating, save and re-use the excess silver nitrate solution; it will become increasingly salty and cloudy, but is good until gone. Hang to dry and rotate as during the salting stage. Sensitizing and drying of sensitized paper should occur under safelight conditions. Sensitized paper will last for several days if kept dry and in darkness.
Exposure: By contact printing under strong ultra-violet light source for 10 to 30 minutes. If you will fix the image for permanence it will be bleached considerably, so you may want to over-expose to compensate for this.
Development: Face-down in very slowly running water. A milky precipitate will appear; continue development for several minutes after the water has cleared. At this point the image will have a very beautiful and continuous purple-brown tonality similar to un-fixed printing-out paper. If you have completely washed out the unexposed silver chloride and excess salt, the image will last in this state for a long time provided it gets little or no exposure to ultra-violet light.
Fixing: For permanence, immerse the developed print for 1-2 minutes in a solution of 50 grams of sodium thiosulfate and 1000 cc water (200 grams per gallon). Wash for 10 to 15 minutes in running water, and hang to dry. As stated before, fixing bleaches the image to a lighter tan color, however, it still maintains a very beautiful and continuous tonality which stands well by itself or makes an excellent base for subtle hand-coloring.