PHOTOMECHANICAL PROCESSES 353 
HARDENING BATH FoR ENAMEL PRINTS ON ZINC.— 
Ammonium bichromate a I51e 27.5 ote 
Chromic acid 0.3 ¢g 2.2%. 
Methyl alcohol 143 ccm 2 1/3\0z: 
Water 1000 ccm 16 oz. 
Immerse the developed plate for from three to five minutes. 
Dye SOLUTIONS FoR FisH-GLUE Prints.—0.5 per cent 
solution of methyl violet or eosine. 
Hatr-Tone ENAMEL FOR COPPER.— 
Le Page’s fish-glue 200 ccm S/S Oz: 
Albumen 131.25 g 2 0z., 44 min. 
. Ammonium bichromate 2.7/5 2 213 gr. 
Ammonia 33 drops 25 drops 
Water 1000 ccm 16 oz. 
Beat the albumen to a froth. Allow to stand 8 hours and add 
the glue and then the salts dissolved in some water, make up 
to bulk, and filter. 
BITuMEN ProOcEss.— 
Syrian asphalt, fine powder 42.5¢ 320 gr. 
Chloroform 400 ccm (6372/5) (0745 
Benzole, anhydrous 600 ccm 9 3/5 oz. 
Venice turpentine WAV) 96 gr. 
Oil of lavender 40 drops 32 drops 
The coated film should be a transparent golden colour. The 
exposure is very long even in sunlight. Develop with recti- 
fied turpentine. 
Etcuinc BatTus For Z1nc.—Weak bath for first bite for 
line or half-tone, 1 per cent nitric acid. Deep etching for 
half-tones, 2.5 per cent nitric acid, 1.875 per cent for fine 
etching half-tones on zinc. For cold enamel: 
Nitric acid 15.6 ccm 4 oz. 
Alcohol, 40% 1000 ccm 16 oz. 
