358 PHOTOGRAPHIC FACTS AND FORMULAS 
film with a velvet roller. Place in water for about 3 minutes 
and then roll up again with the roller; this removes the ink 
and any slight veil can be removed with a wet swab of cotton. 
Free from water drops by lightly touching with blotting paper 
and pin to board to dry. 
Direct PRINTING ON ZINC AND ALUMINIUM.—Sensitise 
with: 
White of egg 62.5 ccm — 1 oz. 
Fish-glue 15.6 ccm V4 oz. 
Ammonia bichromate 7.82 60 gr. 
Ammonia q.S. q.S. 
Water 1000 ccm 16 oz. 
Enough ammonia should be added to make the solution a 
clear lemon yellow. For large plates the volume of the solu- 
tion may be increased by one-fourth with water. 
VANDYKE OR REVERSE Process.—Zinc plates should be 
grained with the graining bath given for line work and coated 
with the following: 
Fish-glue lllg 853 min. 
Ammonium bichromate zie 170 gr. 
Chromic acid 0.13 g 1 gr. 
Water 1000 ccm 16 oz. 
After exposure, under a line copy, develop with plain water 
and dye up with aniline dye. The plate should then be passed 
into a bath of: 
Ferric chloride, 31% sol. 2ccm 16 min. 
Water 1000 ccm 16 oz. 
Leave the plate until the colour disappears, then rinse and 
dry. Treat the plate with asphaltum washout tincture, and 
ink up with the following: 
Bitumen, powdered 4 parts 
Litho chalk printing ink 1 part 
Litho writing ink 1 part 
2 
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