Photogenic Drawing on Salted Paper with Hypo

Talbot’s salted paper process was a printed-out process (POP) meaning the photographs were developed in the sun. The photographs are made by coating paper with a weak salt solution, drying, and coating with silver nitrate, which reacts to additives already in the paper. Salted paper prints have a matte texture and soft image that appealed to a portion of the population despite never achieving commercial success.

Talbot found that potassium iodide (KI) stabilized the image, but it has the tendency to bleach the metallic silver that forms the image. He found that sodium chloride, or salt, gave the best results as a stabilizer by reducing the paper’s sensitivity to light. He changed to sodium thiosulphate, or hypo, in 1839 when it was discovered by his friend and scientist John Herschel. The addition of hypo made Talbot’s “photogenic drawing” paper evolve into what was known as “plain salted paper.”

The sizes of silver particles in printed-out images are smaller than “wavelengths of visible light which leads to a combination of scattered and transmitted light” (Goins). Smaller particles transmit warmer colors, such as yellow and red, and scatter cooler colors, such as blue and green. Therefore, the tiny, or “colloidal,” particles in Talbot’s photogenic drawings and salted paper prints give his printed out images a warm tone. Hypo works by removing the silver chloride from the matrix, which will then shift the refractive index from 2.071 of silver chloride to the refractive index of silver hydrosol (usually close to 1.0). This shifts the absorption band to lower wavelengths, causing images to look yellow-brown and duller. As the prints dry and the image layer contracts, they become more neutral in color and gain slight density.

Goins, Elizabeth, first draft of chapter

Rosenblum, Naomi. A World History of Photography. New York: Abbeville Press, 1997.

Reilly, James M. The Albumen & Salted Paper Book: The history and practice of photographic printing, 1840-1895. Light Impressions Corporation. Rochester, 1980. <http://albumen.conservation-us.org/library/monographs/reilly/chap9.html>

http://www.alternativephotography.com/wp/pop-printing-out-process/printing-out-processes

http://albumen.conservation-us.org/library/monographs/reilly/chap3.html

We concluded from the results of our previous photogenic drawing experiment that 2 coats of 12% sliver nitrate (AgNO3) over one coat of salt solution (NaCl) on Strathmore cold press watercolor paper yielded the best tonal variation. Therefore, we used this process to coat our paper that we exposed with color filters and objects.

We cut the letters “R”, “B”, and “Y” out of red, blue, and yellow cellophane to place on a half sheet of paper to test the effect of color negatives on image formation. Our hypothesis was that the silver emulsion would be more sensitive to blue (shorter) wavelengths than red or yellow (longer) wavelengths.

Four sheets of paper had objects placed on them and the fifth sheet had the “R”, “B”, and “Y” cellophane. They were exposed in the sun for about 3 minutes until they turned a dark grey.

The papers were placed in a water wash, two sodium thiosulphate (hypo) baths, and then a final water wash to fix the images. The images became a yellowish brown and slightly lightened once under the hypo. The color cellophane and Peter’s objects were the only papers exposed under glass and it was interesting to find that they turned out darker than the other three that were exposed with no glass.

The paper beneath the blue “B” was completely darkened while the areas under the “R” and “Y” remained light. The paper under the “B” was dark because light got through the cellophane to the silver emulsion. The only wavelengths that are transmitted through blue cellophane are short wavelengths, or the blue end of the spectrum. Therefore, our hypothesis that the silver emulsion is more sensitive to blue (shorter) wavelengths was correct.

I used a beaded necklace for my salted paper print and although it darkened to a deep purple-grey under the sun, it lightened and turned a yellowish brown under the water and hypo baths. I let my image sit in a water bath for about an hour at my apartment and it seemed to gain contrast and turn to a redder brown. There are very distinct highlights where the beads were touching the paper since the light couldn’t expose that section of the paper.

 




Albumen and Salt Paper group on Flickr:

http://www.flickr.com/groups/1335034@N20/

http://www.flickr.com/photos/hillyfaekillie/5549978731/in/pool-albumen#/photos/hillyfaekillie/5549978731/in/pool-1335034@N20/

http://www.flickr.com/photos/yourmung/5170594181/