The photogenic drawing

The photogenic drawing is a type of image making that uses silver nitrate and salt to create a positive-negative image on the exposed surface. Invented by William Henry Fox Talbot, the photogenic drawing was announced after the discoveries made by Daguerre with his own photographic process. Being reasonably inexpensive and simple, the photogenic drawing was a great advance in photographic image making, the process using basically the same end product that black-and-white photo paper is today.
With the light sensitive silver nitrate applied to the paper, an object or a negative is placed on the surface and allowed exposure until they seemed done, about 5 minutes depending on the mixture. Another method was placing the paper in a camera obscura, also giving an image.



The Procedure
In our experiment, we created our own photogenic drawings, and tested the varying sensitivity to light that different mixtures of chemistry would have.

1. 100% rag paper was labeled and adhered to a cutting board with masking tape for stability and organization
We labeled 12 sheets for different ratios of salt (NaC)l and silver nitrate (AgNO3), and different number of coatings of each
These are the mixtures used:
1. 1 coat 2% NaCl and 2 coats 12% AgNO3
2. 1 coat 2% NaCl and 2 coats 5% AgNO3
3. 1 coat 5% NaCl and 2 coats 12% AgNO3
4. 1 coat 5% NaCl and 2 coats 5% AgNO3
5. 2 coats 2% NaCl and 2 coats 12% AgNO3
6. 2 coats 2% NaCl and 2 coats 5% AgNO3
7. 2 coats 5% NaCl and 2 coats 12% AgNO3
8. 2 coats 5% NaCl and 2 coats 5% AgNO3
9.2 coats 2% NaCl and 1 coat 12% AgNO3
10. 2 coats 2% NaCl and 1 coat 5% AgNO3
11. 2 coats 5% NaCl and 1 coat 12% AgNO3
12. 2 coats 5% NaCl and 1 coat 5% AgNO3

2. Salt solution was applied with a brush and then allowed to dry, either 1 or two coatings
3. Silver nitrate solution was applied with a brush and allowed to dry, either 1 or two coatings
4. A variety of objects were placed upon our paper, including a zippo lighter, car keys, scissors, and pens
5. The paper was set outside in daylight for a 7 minute exposure time, and then brought inside
6. The sheets were peeled from the holder, washed in strong salt water, and then washed in cold water.

Results

We found that more salt is bad for the paper, as it gives less sensitivity to the silver, and the resulting image is very light, where too much silver or not enough salt leads to a dark, overly sensitive and ugly image.



Here are more resources on the subject:
http://www.mhs.ox.ac.uk/features/ephotos/pdtypes.htm
http://www.sugimotohiroshi.com/PhotoDrawing.html
http://www.edinphoto.org.uk/1_early/1_early_photography_-_processes_-_photogenic_drawing.htm