PRINTING-OUT PAPERS 183 
Sodium acetate 5g 38.5 gr. 
Water 1000 ccm 16 oz. 
Printing must be deep; the salt bath prior to toning, and the 
alkaline fixing bath must be used. 
DEVELOPING PRINTING-oUT Paper.—If a printing-out 
paper be exposed for a very short time, so that only a very 
faint image is visible, it is possible to develop it to full inten- 
sity. The first processes were practically physical intensifica- 
tion methods, based on the precipitation of the free silver 
nitrate in the emulsion on the image. As a rule, unpleasant 
greenish tones were obtained. A typical formula is: 
Gallic acid 5¢g 38.4 gr. 
Sodium acetate 10g 77 gr. 
Glacial acetic acid 10 ccm 7/7 min. 
Water 1000 ccm 16 oz. 
This should be diluted with from 5 to 10 parts of water 
before use. A more satisfactory result is obtained with the 
following : 
A. Hydrochinon 10¢g Tf St: 
Alcohol 100 ccm 770 min. 
B. Sodium sulphite, dry 10g 77 gr. 
Citric acid lg 77 Si: 
Water 100 ccm 770 min. 
For use mix 5 parts each of A and B, and add 100 parts 
water. This works slowly, about 15 minutes being required 
for full development. The prints should be immersed in a 
5 per cent solution of salt after development, well washed, 
and then toned. Pyrocatechin gives more violet tones than 
the above; pyrogallol works much more quickly: 
Sodium sulphite, dry 50 g 384 gr. 
Citric acid 10g 77 gr. 
Pyrogallol 10g JF 2%: 
Water 1000 ccm 16 oz. 
