296 PHOTOGRAPHIC FACTS AND FORMULAS 
Alum 20 g 154 er. 
Boric acid 30 g 230 gr. 
Water 1000 ccm 16 oz. 
It is as well to add to this a few drops of fish glue. A piece 
of linen or Canton flannel should be wrapped round a reason- 
ably large pad of absorbent cotton, some of the above solu- 
tion poured on to the middle of the paper, evenly distributed 
with the pad, and then the paper hung up to dry in the dark. 
The exposure will be from 3 to 5 minutes in summer, and 
from 15 to 25 minutes in winter. The paper should then be 
washed in water, but too long washing must be avoided. 
A piece of pigment tissue, the same size as the paper, 
should be immersed in the following: 
Hydrochloric acid 2 ccm 15 min. 
Ferrous sulphate BS 27 St. 
Water 1000 ccm 16 oz. 
This is suitable for normal pictures; for contrasty prints 
reduce the iron salt to 2.5g (19gr.); and for soft prints 
increase to 4.5¢ (35 gr.). When the tissue is quite limp, 
immerse the print in the bath, bring the two surfaces into 
contact, lift out together, squeegee into close contact, and 
leave for from 30 to 60 minutes, the longer time giving 
greater detail in the prints. Development may be effected 
at once, or delayed for some hours if more convenient. 
A later procedure required the following stock solutions: 
A. Hydrochloric acid 28 ccm 1 oz. 
Cupric sulphate 31 ccm 480 er. 
Water 560 ccm 20 oz. 
The working solution was composed of : 
Hydrochinon 0.6 ¢ 9 gr. 
Water 1130 ccm 40 oz. 
Solution A 14 to 28 ccm Y4 to 1 oz. 
For soft pictures of small size from hard negatives, use the 
