Exploring Photographic Chemistry Salted Paper Prints : One of the first methods

Question

Exploring Photographic Chemistry

Salted Paper Prints: One of the first methods tried for making photographs involved first treating paper with a salting solution containing a weak binding agent and a chloride salt. When the treated paper is dry it is then coated again with a solution of silver nitrate. This treatment deposits light-sensitive silver chloride right into the fiber of the paper. The paper can then be exposed in a camera obscura, pinhole camera, or printed out under a negative to produce an image. Sometimes this method was referred to as photogenic drawing. Today you will prepare these salted paper prints. Two different salting solutions and the silver nitrate sensitizing solutions have been prepared for you. The composition of these solutions is given at the end of the experiment for your own future reference. Each group (work with ONE partner) will try two different salting formulas, (1) gelatin-based and (2) starch-based, and compare the results of the two. Directions 1. Obtain 2 pieces of 4 x 5 watercolor paper. Mark one side (which will remain untreated) with the type of salting solution used on each. 2. In a tray in the hood, apply the salting solution (either gelatin or starch) to one side of a piece of heavy watercolor paper with a sponge brush. It is important to get an even coating so spread the solution first in one direction, then spread again at a right angle to the first direction, then spread a final time in the first direction. This may be carried out under normal lighting. You can allow the paper to dry naturally or using heat. Once dry, the treated paper will keep indefinitely. Be sure it is completely dry before proceeding to step 3. 3. In subdued light, brush sensitizing silver nitrate solution onto the dry salted paper using the same technique as previously to ensure even coating. 4. Dry the paper (hot air gun or oven) or let it dry in the dark. The paper will keep about a week if dry and in the dark. 5. Print the dry paper by placing a negative image on top of the paper and exposing it to sunlight or a UV light source. The image should be allowed to change to a rather deep or dark tone with shadows having a bronze or metallic sheen. You may have to expose it for a long time for this to happen. 6. Wash the print in several changes of tap water until all cloudiness in the water has been removed. The print tone will lighten and become reddish. 7. Fix the image by soaking for 10 minutes in a solution of fixer (also called hypo, a solution of sodium thiosulfate) with frequent agitation. 8. Thoroughly wash fixed prints for about 10 minutes under a gentle stream of running water. Gelatin Salting Formula Starch Salting Formula Water 280 mL Water 280 mL Gelatin 2 g Corn starch 5 g Sodium citrate 6 g Sodium citrate 6 g Ammonium chloride 6 g Ammonium chloride 6 g Sensitizing Solution Distilled water 30 mL Silver nitrate 4 g

Question

Why does a Starch solution work better than a gelatin solution in traditional photography.

Explanation / Answer

A startch solution works better than a gelatin soluion in traditional photography as startch is more stable than gelatin in solution. The solution prepared sing startch forms a better emulsion which is stable for longer periods of time whereas, the one prepared from gelatin does not remain the same after standing for longer period at room temperature.

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.