266 PHOTOGRAPHIC FACTS AND FORMULAS 
or Ferric nitrate 400 g 634 oz. 
And add in the same way: 
Uranium nitrate 6g 46 gr. 
or Uranium chloride 200 g 3% oz. 
Finally, add: 
Ferric chloride solution, 
sp. gr. 1.453 210 ccm 3Y oz. 
Filter through muslin and coat well-sized paper therewith. 
The exposure will be from 3 to 6 minutes in sunlight. Place 
the print face up on a sheet of zinc or glass, and with a roller 
lightly charged with printer’s ink roll up the surface until 
uniformly grey. Immerse the inked print in cold water, 
transfer to a metal or glass plate supported at an angle, and 
allow a spray or stream of water to play over the surface; 
with a pad of absorbent cotton gently rub the print. The 
exposed parts will be gradually dissolved, leaving only the 
inked parts. 
TRUE-TO-SCALE Process.—A cheap and ready process for 
obtaining a few, about 25, pulls in printer’s ink from line 
drawings, etc. A good black original is the best. Ferro- 
prussiate or cyanotype paper should be exposed under the 
plan or drawing, and without development laid down on a 
“graph” or jelly, gently rubbed into contact, and immediately 
stripped. The jelly is now rolled over with a good letter- 
press ink with a composition roller and it only takes on the 
lines. A piece of paper is now laid on the jelly and rolled 
over lightly with a light roller, and, on lifting, the impression 
will be found on the paper. Inking must be done before each 
pull. The jelly can be made as follows: 
Glue 500 g 8 oz. 
Water to make 1000 ccm 16 oz. 
Allow to soak for some hours, melt with heat, and add: 
Gelatine 62.5 g 1 og. 
