This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Developing Solutions. The use of prepared developing powders is recommended to the beginner for his experiments in developing plates or films. These powders can be procured from any dealer in photographic supplies. If a regulation finishing outfit has been purchased the chemicals included therein can be used. Prepared developing chemicals only require dissolving in a certain quantity of water, the directions for which are always given on the package.
117. In the graduate, which has been thoroughly cleansed, place the amount of water specified in the directions. The developing powders come, generally, in two small packages, these again being put up in one larger package, or, the powders are inserted in both ends of a glass vial, separated by a cork or wad. Carefully open the larger of the two packages, or remove the cork from that end of the vial containing the larger quantity of chemical, and slowly shake the contents into the water in the graduate, stirring rapidly until all is thoroughly dissolved. This chemical, which is generally the sulphite and carbonate of soda, if not made to dissolve immediately by rapid stirring will cake and cause considerable trouble, being left in the solution in the form of a precipitate. When thoroughly dissolved add the contents of the smaller package, or the smaller quantity of chemical in the vial, which is the developing agent. The developer is now ready for use.
Fixing Solution. After mixing your developer, next prepare the fixing solution. Take a handful of hypo and place in the 4x5 tray which you intend to use for hypo only, and fill this tray about two-thirds full of water. This should give a proportion, approximately, of one ounce of hypo to four ounces of water. Stir this with a small wooden paddle, or glass stirring-rod, until all of the hypo has been dissolved. Under no conditions use this tray for any other purpose than for fixing. Always wash the hands thoroughly after handling any chemical. Hypo, especially, will give no end of trouble if the least trace of it is carried to any other bath.
Development. Everything is now in readiness so that development of the exposed plate may be proceeded with. With the developing tray carefully rinsed and the ruby lamp lighted, now close the door of the dark-room, so that there is absolutely no other light in the room except that which comes from the ruby lamp. Draw the slide from the plate holder and remove one plate. Sometimes the plates are liable to stick in the plate holder. By pushing down with the thumb on the small spring at the end of the holder, gently tapping the holder on the other end, and slightly tipping forward, the plate will fall into your hand.
120. As soon as the plate has been exposed an image has been formed, although invisible until acted upon by the developer.
121. After removing the plate from the holder, place it in the tray for developing, being sure that you have the face or film side up. Pour sufficient developer over the plate to cover it, and in doing so, care should be taken that the developer is flowed evenly over the entire surface of the plate, to drive off all the air and not allow any air-bells to form. If the developer is carelessly thrown onto the plate, or if the plate is dropped into the developer, small air-bells are liable to form on the surface of the film, which will prevent the action of the developer on the portion of the film which they cover and thus cause undeveloped spots. The plate should never be placed in water before development. In the case of films, however, it is preferable to wet them in water before placing them in the developer.
122. Always use enough developer to fully cover the plate. Four ounces of solution are sufficient for a 4x5 tray. After flowing the developer over the plate, the tray must be rocked gently, and the development carefully watched. In from 20 to 30 seconds the image will begin to appear. If the developer is cold, the image will be much slower in making its appearance; yet it is advisable that the temperature should not be over 65 deg. Fahr. The image will gradually grow denser, as development proceeds, until finally the plate is nearly black. At this stage it should be carefully examined, to observe the strength of the development.