318 PHOTOGRAPHIC FACTS AND FORMULAS 
faintly visible. Immerse in running or frequently changed 
water, until all trace of yellow disappears. Then immerse in 
water at 28° to 30° C. (82° to 86° F.) for one minute, imme- 
diately place face up on a sheet of glass or flat board, and 
remove surface moisture with fluffless blotters or a soft linen 
pad. Finely powdered lampblack or other powder should be 
dusted over the surface through fine muslin; a small sieve 
can easily be made from a lidless box. Then a soft round 
badger brush should be used with circular strokes to distribute 
the powder, which should only adhere to the unexposed parts. 
When the image is fully visible, the print should be exposed 
to the sun or in a moderately warm oven, not over 60° C. 
(140° F.), until completely dry. At this temperature the 
gelatine softens, and the powder sinks slightly into it. When 
thoroughly dry, immerse in cold water until it lies quite flat, 
then place face up on a board, and rub the surface gently 
with a soft pad until the ground is white. Should the powder 
not adhere sufficiently to the lines, the powdering operation 
may be repeated as often as necessary, a warm water bath 
being used each time, and, if necessary, the temperature raised 
a few degrees to thoroughly soften the gelatine. The print 
then only requires drying. ! 
THE ANILINE Process (Willis) —The basis of this pro- 
cess is the reduction of a bichromate by the action of light 
and the formation of an aniline colour on the exposed salt 
by the vapour of aniline or like compound. 
Well-sized paper should be floated on (Reynolds) : 
Potassium bichromate, 
sat. sol. 1000 ccm 16 oz. 
Sulphuric acid 45 ccm 345 min. 
Or (Dawson) : 
Ammonium bichromate 104 ¢ 798 gr. 
Glacial phosphoric acid 42 to 126g 323 to 968 gr. 
