The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Development and Developers
Hydrochloric acid ... ... ... ... i oz.
Saturated sol. alum ... ... ... ... 19 ozs.
washing the plate again after the operation.
Messrs. Lumiere & Seyewetz state that some of the incon-veniences ordinarily experienced with the pyrogallic developer, such as the staining of the finger-nails and the occasional lifting of the film, are largely due to the use of caustic and carbonated alkalies, and they have found it advantageous to use the alkaline salts of the tribasic acids - phosphoric and arsenic, for instance - not only in the case of pyrogallic acid, but also with hydroqui-none, eikonogen, metol, or glycin. Their pyrogallic developer is prepared as follows : -
A.
Water ... ... ... ... ... ... 1 oz.
Pyrogallic acid ... ... ... ... ... 30 grains.
Anhydrous sulphite of soda ... ... ... 45 ,,
B.
Water ... ... ... ...        ...        ...        7 ozs.
Phosphate of soda ... ...        ...        ...    100 grains.
Anhydrous sulphite of soda ...        ...        ...      45 -..
For use, mix 20 volumes of A with 140 volumes of B.
The Messrs. Lumiere, in conjunction with M. Seyewetz, have made a more strikingly new departure, based on the observation that certain ketones and aldehydes may replace the alkali in developers made up with the usual phenolic reducing agents. Sulphite of soda, Acetone (q.v.), and hydroquinone, pyrogallic acid, or paramidophenol will give a practically useful developer; that with hydroquinone being slow, and with either pyrogallic acid or paramidophenol being rapid. That the reducing action is not due to the acetone is evidenced by the fact that acetone and sulphite alone - or rather, one should say, in water as a medium, will not act as a developer. The following formulae are given T -
Pyro-acetone Developer (rapid).
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