Photography in the Studio and in the Field / A Practical Manual Designed as a Companion Alike to the Professional and the Amateur Photographer

by Edward M. Estabrooke

It is not necessary to make up the full amount of 2 oz. pyro at one time.

In the foregoing two formulæ will be found all that is necessary for making good negatives by either process.

Every box of plates that is put up for sale carries p177 with it the formula supposed to be best for that plate. There are other forms of development that produce good work. The following is one of them:

FERRO-CYANIDE OF POTASSIUM DEVELOPER.

Make a saturated solution of yellow prussiate of potassium and dilute with an equal bulk of water; add 2 drops of ammonia and 2 grains of dry pyro to each ounce used.

The solution can be used repeatedly until exhausted. Four ounces of this solution would contain 8 grains of pyro, which is enough to develop 2 8×10 plates, or their equivalent of smaller plates. Mix only the amount that will be used at one sitting.

It will be noticed in all the foregoing formulæ that the matter of greatest uncertainty is the exposure of the plate; you never can tell if your plate is properly exposed until you begin to develop, and then if your picture flashes out at once it is too late to correct by modifying the developer.

The theory of development is that the pyro is the developing agent and gives the strength.

The soda, or ammonia, as the case may be, gives the detail. The bromide is a restrainer, and to a certain extent will correct over-exposure. Sulphite of soda, citric acid and sulphurous acid are used to keep the pyro from oxidizing.

Therefore, when developing a plate, say a 5×7, put it in the tray and pour over it the amount of pyro necessary to develop such a plate, say two grains in four ounces of water, let the plate remain in this solution for a short time, in the meantime take of your alkaline solution the amount you would use for the p178 same size plate, but add only a small portion to the solution covering the plate. To do this pour off the pyro solution into a graduate and add a drop or two of the alkaline solution, soda, potash or ammonia, whatever it may be, then turn the solution back on the plate and watch for the effect; if in a few minutes there is no change, then add more of the alkaline solution in the same manner, and in a short time the image will begin to appear; if it comes up too slowly, give it the remainder of the alkaline solution, and unless the plate has been under-exposed the image will come out and strengthen gradually until it has well sunken into the plate, when it may be removed and washed.