271. Formula For Developing With Pyrogallic Acid

Formula For Developing With Pyrogallic Acid.

Stock Solution No. 1

Water..............

24 ounces

Pyro...................

1 ounce

Sulphuric Acid...............

5 drops

Stock Solution No. 2. Sulphite of Soda (Anhydrous) Hydrometer test 70, or if by weight,

Sulphite of Soda (Anhydrous)...........

1 ounce

Water...............

8 ounces

Stock Solution No. 3.

Carbonate of Soda, Hydrometer test 40, or if by weight,

Carbonate of Soda (Anhydrous).....

1 ounce

Water..........

10 ounces

If crystal sodas are used you will require 2 ozs. in place of 1 oz. anhydrous, as the anhydrous is twice as strong as the crystals.

We advise the use of the very best sodas. Do not buy the commercial brands.

To prepare this formula, first place 24 ozs. of water in your graduate; add the pyro, dissolving it thoroughly; then the drops of sulphuric acid should be added by holding the acid bottle in your right hand, with the little finger at the bottom of the bottle. Withdraw the stopper and hold your stirring rod to the mouth of the bottle, which will allow you to measure out the 5 drops very carefully.

272. To develop, take 1 oz. of No. 1; 1 oz. of No. 2; 1 oz. of No. 3, and add 6 ozs. of pure water in winter, and 8 ounces in summer. If your plates develop a yellow color, strengthen the sulphite, if there is a lack of color and the plate is a blue-gray, reduce the strength of your Sulphite Stock Solution, but use the same quantity.

273. Always bear in mind that sulphite of soda regulates the color value of the plate; carbonate of soda gives detail; and pyro, being the developing agent, gives strength and contrast.

274. If your negatives are yellow the sulphite is not strong enough. For instance, if you are using sulphite at 70 hydrometer test, then you must strengthen it to perhaps 80 test, all other chemicals remaining as they are. The color of the negative is regulated entirely by the strength of sulphite of soda. It will seldom, if ever, be necessary to change the strength of the carbonate of soda.

275. Pyro, which is the developing agent, is used to produce strength (density). If your plates develop up con-trasty, use less of No. 1 (the Pyro Stock). This developer will work well with any brand of plates by following the above directions. If you are using a brand of plates that

Preparing Chemicals: Developing with Pyro. 159 will build up (strengthen) quickly, use more water. If, on the contrary, you cannot obtain the desired strength, reduce the amount of water, thus making the developer stronger.

276. For Seed, Standard and Stanley plates, also films, use according to formula; for Cramer plates, use 10 drams of pyro and 9 ozs. of water; for Hammer plates use only 6 drams of pyro and 8 ozs. of water, the sodas remaining the same for all plates.