"First catch your hare, then cook him," says the old proverb, and providing a plate has been exposed in accordance with the foregoing instructions, and our dark-room being at command, we may finish the first stage of our work and make the perfect negative.
As previously pointed out the action of light on the sensitive surface is an invisible one, the salts of silver, with which the plate is coated, being to all appearance just the same as when the plate was inserted in camera, or dark slide, or changing box. As the exposure has not in any way decreased the sensitiveness of the plate, great care must be taken till development is concluded that no white light reaches the plate or film, and when we say no white light we mean no light excepting that from a safe dark-room lamp. We have known beginners at photography explain that they have used every care, and on enquiry find they did just glance at the plates late at night in a room which had no direct light, but opened on to a passage or courtyard.
Supposing we have only a few plates to develop we shall prefer to use a dish, and there is always pleasure in seeing the gradual growth of the image when developing in a dish that is absent when using a tank.
As for the developer, it is often said that any developer will suffice for a properly exposed plate, but we have a strong preference for a Pyro developer, for, as a rule, it gives prints of better quality. Old " Pyro " users know what we mean, and although admitting the cleanliness and very beautiful-looking negatives obtained with other developers we maintain that there is a quality in prints from pyro negatives - particularly in platinotype - which is lacking when some other reducing agents are used.
The formula we favour is as follows : - No. 1 Solution. Take 1 oz. Pyrogallic acid, 1/2 oz. Metabisulphite of potash, place in a 10 oz. bottle, fill with water and label Pyro 10%. c
No. 2 Solution. Take 4 oz. Carbonate of soda, 4 oz. Sulphite of soda, place in a 20 oz. bottle, fill with water and label Soda 20%.
Then to each 1 1/2 ounces of water add 40 minims of the No. 1 Pyro Solution and 1/2 ounce of the No. 2 Soda Solution. If the plates tend to give soft results the Pyro Solution may be increased to 60 minims (1 dram). Use the developer at a temperature of 65°F, or "just off the chill."
Place the negative in a clean dish and don't remove the " backing," if a backed plate ; use plenty of solution, which flow quickly all over the surface, taking care not to get air-bells ; note the time-by your watch and cover the dish with a piece of cardboard or any other screen. Keep the dish slightly moving, and if properly exposed the image will commence to appear in about thirty seconds. With most brands of plates this developer will develop a good brilliant negative, suitable for platinum printing in five minutes, although other makes, such as Ilford Monarch, require about eight to ten minutes. In any case don't remove the plate from the developer till it has been sufficiently developed, and it is better to carry the action a little too far than not far enough. The image will apparently be lost on the surface of the plate, and it will seem to blacken all over - except the edges which were covered in the dark slide - and be entirely ruined. If the plate was " backed ' the backing should now be removed, which is done by brushing it off with a stiff dish brush in a dish of clean water. The image may, at least in the sky portions, be now visible on the back of the plate. Give a rinse in a dish of water and immerse in a Fixing Bath, made as follows :
Hyposulphite of soda
Metabisulphite of potash or Metabisulphite of soda
The hypo and water will do quite well by themselves, but the metabisulphite of soda not only keeps the bath clean and tends to remove stain from the negative, but it also hardens the film and helps to prevent frilling. When hypo and water are used alone the plate must be kept in the dark-room till fixed, unless it has been thoroughly washed before immersion in the bath. The metabisulphite makes the bath acid and this destroys the active power of the developer in the film, so the same care about light is not necessary.
The use of the fixing bath is to entirely remove all the creamy-looking silver compound contained in the plate and which was in excess of the quantity used to form the negative image. Even when this is all removed and the plate seems clear, it should be kept for a few more minutes in the hypo bath, as there are some salts which, although invisible, are detrimental to the plate and must be removed by the fixing bath.