PHOTOMECTANICAL | PROCESSES SoD 
Substratum. 
Whites of fresh eggs 312 ccm 5 oz. 
Sodium silicate 125 ¢ 202) 
Water 1000 ccm 16 oz. 
Beat the whites to froth and allow to settle, filter and add the 
other ingredients. Pour a little on the plate, drain slightly 
and place on leveled stand to dry. Or: 
A. Gelatine I5¢ bison: 
Water | 500 ccm 8 oz. 
B. Alum 10¢ 80 gr. 
Water 500 ccm 8 oz. 
Dissolve the gelatine by heat, add the alum solution warmed 
up, and add 
Sodium silicate sol. 46g 34 OZ. 
The plates should be warmed and the solution applied with 
a broad camel-hair brush and dry. A stock of plates may be 
thus prepared, but they should be rinsed in water and again 
dried. 
Sensitive Solution. 
Hard gelatine 46¢ 350 gr. 
Water 1000 ccm 16 oz. 
Allow to soak for 30 minutes and melt and add: 
Potassium bichromate 16.5 ¢ 126 gr. 
and filter. Allow 44 min. to every 100 sq. in. (682 ccm per 
square meter). Place the plates in the drying box and warm 
up to 48° C. (120° F.), carefully level and coat. The tem- 
perature of drying must not exceed 54° C. (130° F.). After 
exposure wash in water at 15° C. (60° F.) until all trace of 
yellowness has disappeared, then dry. 
Etching the Plate. Actually a moistening solution, there 
being no etching action. The plate should be rinsed in water, 
blotted off and covered with a mixture of 3 parts glycerine 
and 2 parts water for about half an hour. Or equal parts of 
