Collodion-albumen process
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The Collodion-Albumen process is one of the early dry plate processes, invented by Joseph Sidebotham in 1861.
The process lacked economical success because the plate was much less sensitive (about 1/4) and tended to have harder contrasts than wet plates. While the first was acknowledged by Sidebotham, the latter were disputed by him indicating the fact that the 1860 gold medal for the best landscape photography was made with a Collodion-Albumen plate (Recreative Science, 1861 P 43).
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[edit] Why does it work?
There are several compounds unstable to light in this mixture, mainly silver iodine and silver bromide. These decompose and leave silver that is oxidized by the developer (Pyrogallic Developing Solution). The excess of silver iodine and silver bromide are stabilized by the fixing bath. The Albumen mixture just encloses the Collodion in a dry environment.
[edit] Making a Collodion-albumen plate
First prepare collodion and silver nitrate as in the Collodion Process, then prepare albumen by mixing 150 grams of egg white, 40 grams of water, 3 milliliters of aqueous solution of ammonia(liquor ammoniac), 160 milligrams of potassium iodine, 30 milligrams of potassium bromide and 0.1 milliliters of tincture of iodine (7%). Beat the egg white until it is foam and add the other components into the water and dissolve. Mix the solution and the egg foam. After mixing filter with a sieve or sponge, mostly to free the mixture of air bubbles.
In a dark room make a wet plate and rinse off in water, after that pour some albumen mixture over it and cover the whole plate. The excess albumen can be filtered and returned to its container. Now, in dim light, dry the plate. This plate is not yet sensitized and can be stored in dim light in this state for months as the albumen is opaque enough not to let light through.
To sensitize the plate you need a mixture of 90 grams of silver nitrate, 130 milliliters of glacial acetic acid in 1000 milliliters of distilled water. In a dark room put the plate for about a minute in a tray with the aforesaid mixture. After that, wash off in running water and dry. Once dried this plate can be stored in complete darkness for about a week, with low temperatures for two weeks.
The sensitivity of this plate is about 1/0.5 ISO.
[edit] Developing a Collodion-albumen plate
First you will have to prepare what Sidebotham called the Pyrogallic Developing Solution, the Silver Developing Solution and the fixing solution.
The Pyrogallic Developing Solution consists of 1300 milligrams of Pyrogallic acid and 650 milligrams of citric acid dissolved in 300 milliliters of water. The Silver Developing Solution consists of 650 milligrams of silver nitrate in 300 milliliters of water. The fixing solution consists of 40 milligrams of Hyposulphite of soda in 300 milliliters of water.
The plate must be level to be developed. You can achieve this by using a stand or a tray on a level table. Too much of an incline could make the emulsion run destroying the image. Red, brown or green safe light can be used during this process.
First wet the plate in water for a few seconds and then place it on the stand or in the tray. Now pour the Pyrogallic Developing Solution over it. If the image is in a tray once should be enough, on a stand repeat several times. The negative image should now appear. If the contrasts on it are too hard put it in another tray with Pyrogallic developer and a few drops of Silver Developing Solution (careful as too much of it can spoil the developer). If using a stand pour a beaker with the mixture over it.
Once you are satisfied with the negative or the developing process stops place the plate in the fixing bath and turn on the light. Once the blue hue disappears from the plate you can water and dry. The negative is more durable if covered in shellac or clear varnish.
[edit] Sources
The Collodio-Albumen Process of Photography, Joseph Sidebotham (London : Recreative Science Vol II 1861)
History of Photography, Josef Maria Eder (Dover Publications, Mineola, NY, 1945)
