268 PHOTOGRAPHIC FACTS AND FORMULAS 
dry plates in a 2 per cent solution of tartrazin. The exposure 
varies from 30 seconds to 2 minutes, according to the sensi- 
tiveness of the paper and the strength of the light. The 
developer should be preferably hydrochinon well restrained 
with bromide, as generally used for line work. Printing-out 
paper may be used in the same way. And also the following 
(Albert) : 
Albumen 60 ccm 460 min. 
Fish glue, Le Page’s 40 ccm 307 min. 
Ammonium bichromate 45 ¢g 346 gr. 
Water 1000 ccm 16 oz. 
Or: 
Fish glue 37.5 ccm 288 min. 
Ammonium bichromate 3g 23 gr. 
Grape sugar 3.25 g 25 gr. 
Water 1000 ccm 16 oz. 
Dissolve the sugar in about one-fourth of the water before 
adding the other ingredients. Glass should be coated with a 
whirler and exposure is best effected with a half-watt lamp 
at a constant distance, the glass being placed with the coated 
side down on the drawing. Development is effected with hot 
water, and the print can then be stained up with a solution 
of a dye, such as chrysoidin, water soluble nigrosin, or by 
immersion in a 4 per cent solution of potassium permangan- 
ate, which gives a deep brown image of manganese dioxide. 
CopaLt-IrRoN Printinc (Burian)—This process seems 
more suitable for line drawings than prints from ordinary 
photographic negatives. 
Oxalic acid 8¢g 61.5 gr. 
Water 30 ccm 230 min. 
Heat until dissolved, and add: 
Ammonium oxalate, neutral 24¢ 184 gr. 
When dissolved, add: 
