320 PHOTOGRAPHIC FACTS AND FORMULAS 
The image should appear in a few minutes and will be a dirty 
blackish-green. The colour is somewhat dependent on the 
duration of the aniline fuming; the shorter this is the bluer 
the final print; the longer the time the more blue-black the 
colour. The fuming time is dependent on the exposure. 
When the image is intense enough, immerse the paper in 
water, running or frequently changed, until the whites are 
pure. If the whites will not clear, immerse the print in a 
1 per cent solution of sulphuric or 3 per cent hydrochloric 
acid; then wash, and the green will be formed, which can be 
converted into blue by treatment with a 1 per cent solution of 
ammonia. 
ANILINE BLACK OR ENDEMANN’S Process.—This is also 
sometimes called vanadium printing. Aniline black is formed 
by the action of a vanadium salt. The sensitiser is: 
Salt 31g 238 gr. 
Potassium bichromate She 238 gr. 
Sodium vanadate 0.043 g 0.33 gr. 
Sulphuric acid 65 ccm 500 min. 
Water 1000 ccm 16 oz. 
Well-sized paper, preferably sized with a 2 per cent solution 
of gelatine, is floated on the above or the solution may be 
applied with a brush and dried. Exposure should be about 
7 minutes in diffused light, and the print should then be 
exposed to the vapour of a 2 per cent solution of aniline in 
warm water, which should be heated in a dish. The image 
will appear in a brown colour and the paper should then be 
exposed in a very damp room or box at 24° to 30° C. (75° 
to 86° F.) for about 2 hours, or until quite black. Finally, it 
should be washed with dilute ammonia, 1:6, and dried. 
FEERTYPE, PRIMULINE AND DIAZOTYPE PROCESSES.— 
These processes are but rarely used and are more applicable 
to fabrics than to paper. They are based on the light-sensi- 
