First make two stock solutions as follows:

No. 1. A saturated solution of oxalate of potash (a pint or quart) and test with blue litmus paper. If it does not show an acid reaction dissolve a little oxalic acid in water and add enough to the solution to cause the blue test paper to turn red.

This solution should be filtered for use.

No. 2. Make a saturated solution of pure sulphate of iron, and to one quart add three or five drops of sulphuric acid, to prevent oxidation, and filter.

Now, to develop a 5x8 plate, take three ounces of No. 1 and to this add one quarter of a dram of bromide of potassium solution (which is water one ounce, bromide of potassium twelve grains), then add half an ounce of No. 2; this forms the developer.

Then transfer the plate to a developing disk, and pour over it the developer. If the picture comes out gradually and develops sufficiently, it is good so far, but if from under-exposure the details hang back and refuse to develop further, then add two drams, or half an ounce, more of No. 2, which will bring out the picture with full details, unless greatly under-exposed.

Never exceed one ounce of No. 2 (iron) to three ounces of No. 1 (potash), for if you do you will form a sandy deposit and discontinue the action of the developer.

Always develop until the picture seems sunken into the surface. Do not judge by looking through the negative only. Wash and fix in hypo, 1 ounce; water, 8 to 10 ounces. After fixing, wash well.

For pictures taken instantaneously, use no bromide in the developer.

Cooper's Soda Developer

"No. 1. Anthony's Sodium Sulphite Crystals..3/4 lb.

Distilled water.................. 2 qts.

Anthony's Pyrogallic Acid......... 2 ozs.

No. 2. Anthony's Sal Soda Crystals ......... ½ lb.

Water...........................2 qts.

To develop, take

No. 1.................................2 ozs.

No. 2................................2 "

Water................................2 "

For restraining over-exposure use the above quantity of developer, one-half to one dram of

Bromide potassium.....................1 oz.

Water.................................6 "

"It is always advisable to use two developing trays, and have the normal developer in one and the restrained developer in the other. Then, by changing the plate from one tray to the other, the character of the negative is under full control. Four to six plates can be developed in one lot of developer.

"This developer can be used for a number of plates, and gives fine negatives of good printing quality.

"After development, return your old developer to a stoppered bottle, and keep for commencing development.

"The reason for doing this is as follows:

"As a rule, I give a little more time than necessary to make a full-timed negative, and, by commencing with the old developer, give the high lights a start of the shadows, which I can readily soften afterwards by the use of a stronger developer at the finish, thus obtaining the sparkling high lights so much admired in the wet plate; and so seldom found in the average Dry Plate Pictures.

"This developer never becomes muddy, and may be used repeatedly with fine effect.

"Always place plates in a strong solution of alum after developing and rinsing, and before fixing. This gives brilliancy to the negative and prevents the possibility of softening.

"In the use of the above formula it is important that the best Chemicals be employed."

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

In the foregoing two formulae 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 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: