The chemical outfit for making negatives comprises the following items: Two vulcanite trays, a glass graduate, a set of small scales, and weights for weighing chemicals, a ruby lantern, a bottle of varnish, a package of dry plates and of chemicals, a small quantity of bromide of ammonium, neutral oxalate of potash, protosulphate of iron, hyposulphite of soda, alum, and sulphuric acid. These chemicals are not dangerous, neither will they injure any one who handles them, and they do not emit offensive odors. Silver stains, and the disagreeable smell of collodion belong to the old or “wet” process.
At a convenient time take the plate holder into the dark room, illuminate it with ruby light, take the sensitive plates out of the holders, being careful not to touch their surfaces. Hold them by the edge. Place one of the sensitive plates, film side up, in a tray partly filled with water. While it remains there, mix this solution: Neutral oxalate of potash, 5 ounces; bromide of potassium, 20 grains; water, 20 ounces. If the solution does not turn blue litmus paper red, add a few drops of oxalic acid, enough to make it do so. A graduated glass is used to measure out the liquids. After rinsing the glass out, mix a second solution made as follows: Protosulphate of iron, 5 ounces; water, 20 ounces; and acidulate it with 20 drops of sulphuric acid. Both of these solutions keep well. Now combine a quarter of an ounce of the latter solution with two ounces of the former and mix them well. Pour off the water in the tray containing the gelatine plates. Be certain not to touch the sensitive side of the plate. Flow the combined developing solution over the plate and displace, by a touch of your finger, any air bubbles that may form. After a short time traces of the image on the sensitive film will appear. If they do not, pour the developing solution back into the tray and add a quarter of an ounce more of the iron solution. Pour the strengthened solution over the plate and look at it intently. In a short time the details of the picture may be dimly seen. Wait patiently till the milky white appearance is changed to a grey color, and then pour off the developer into a developing bottle, if you have one. Wash the plate in two changes of water. In the unused tray mix a solution composed of 4 ounces of hyposulphite of soda and 20 ounces of water. (Label this tray “Hypo.,” and do not use it for any other purpose.) A plate lifter is a convenient device for taking plates out of the solutions or baths. Change the plate to the hypo. tray, and let it remain there until every vestige of the milky white appearance has vanished, even from the under surface of the plate. The plate can now be examined by white light, which has no effect upon it at this stage. Wash it thoroughly. A negative washing box will be found to be of great assistance. If this washing of the plate is not done thoroughly, the hyposulphite of soda crystals will adhere to the plate and mar the picture. Meanwhile rinse out the tray first in use and partially fill it with a solution consisting of 20 ounces of water and all the alum it will hold in solution. Allow the plate to remain in the alum bath five minutes. Cleanse your hands from any adhering soda solution. Again wash the plate, and set it on edge to dry in a negative rack.
All the preceding instructions can be briefly summarized.
1. Put some sensitive plates into dry plate holders.
2. Make the exposure.
3. After taking a plate out of the holder, place it in a tray filled with water.
4. Drain off the water and put the plate in the mixed developing solution.
5. Wash the plate and place it in the soda solution.
6. Wash the plate and give it an alum bath.
7. Wash the plate and set it in the rack to dry. When perfectly dry, coat the plate over with negative varnish, and have that coating dry and hard. Now it may be touched by the fingers.