278 PHOTOGRAPHIC FACTS AND FORMULAS 
potassium bichromate may be used instead. Omission of 
these naturally gives softer effects. Sensitiser A with arrow- 
root sizing tends to brownish-black tones, but with plain, not 
arrowroot-sized, drawing papers, black tones; with gelatine- 
sized papers blue-blacks are given. A and B give too hard 
prints with contrasty negatives; then C should be used, as 
this gives softer results. 
After printing until the image is faintly visible in greyish- 
violet against the pure yellow unprinted parts, the print 
should be rapidly and evenly immersed in either of the 
following developers: 
Neutral potassium oxalate 250 g 4 oz. 
Water 1000 ccm 16 oz. 
Or: 
Neutral potassium oxalate 100 g 770 gr. 
Potassium phosphate 50 g 384 gr. 
Water 1000 ccm 16 oz. 
It is preferable to take hold of both ends of the paper, im- 
merse one end in the developer, face down, draw right 
through the solution and then turn face up. Development 
is comparatively slow and takes from 1 to 2 minutes; the 
dish should be gently rocked. As soon as sufficient depth is 
attained, immerse the print, without washing, in: 
Hydrochloric acid 20 ccm 154 min. 
Water 1000 ccm 16 oz. 
face downwards. The dish should be rocked. After 5 min- 
utes, remove the print to a second dish of water acidulated 
as above, and, after 15 minutes, remove to a third dish of 
half the above strength of acid. At the end of 15 minutes, 
place the print in running water for 30 minutes, then blot off 
between blotting papers, and dry. Dilution of the developer 
gives more brilliant prints; or the same result may be ob- 
tained by adding 2 to 5 per cent of a 1 per cent solution of 
