Before using mix--

Pyro solution A 20 c. c.

Soda solution B 20 "

Water 20 "

The developer acts about one and a half times slower than the ordinary

pyro soda developer, approaching to the latter pretty nearly, and

gives to the negatives an agreeable color and softness, with clear

shadows. If the negatives are to be thinner, more water, say 30 to 40

c. c., is taken. If denser, then the soda is increased, and the water

in the developer is reduced. An alum bath before fixing is to be

recommended.

An advantage of this development is the great durability of the

pyro-meta sulphite solution. The cost price is about the same as

that of the ordinary pyro developer. At all events, it is worth while

to make further investigation with the metabisulphite of potassium,

the same being also a good preservative for hydroquinone

solutions.--_Photographische Correspondenz; Reported in the Photo.

News._

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Scientific American Supplement, No. 717, September 28, 1889 · 第 33 / 38 题