LANTERN SLIDES 331 
This gives a fine grain and takes the pencil well. To make 
it again transparent, coat with: 
Sandarac 30 g 240 er. 
Mastic 30 g 240 gr. 
Ether : 1000 ccm 16 oz. 
DIAGRAM LANTERN SLIDES.— 
Canada balsam 4 parts 
Pure turpentine 8 parts 
Liquid siccative 1 to 2 parts 
Mix thoroughly, and add as much lampblack as will give it 
the consistency of an ointment. Coat glass evenly with a 
badger hair softener. Or: 
Syrian asphalt 50 parts 
Yellow Venice turpentine 10 to 12 parts 
Linseed oil or varnish. 15 parts 
Pure turpentine 15 parts 
Melt the asphalt and Venice turpentine in the turpentine by 
heat, and add the linseed oil with continual stirring. Add 
enough lampblack to make it as thick as ointment. Well- 
cleaned glass should be coated with this until opaque, and 
allowed to dry; then rubbed over with a little lampblack 
rubbed up with gum water. This will be repelled at first but 
with continual working will take. A good-sized darning 
needle mounted in a wooden handle may be used as the 
graving tool. Broad surfaces may be scraped out with a 
sharp knife. The above give. white lines on a black ground. 
DEVELOPMENT.—Numerous formulas have been proposed 
for lantern slide plates. A few American manufacturers’ 
formulas are given, and are adaptable to other brands. 
Hammer Transparency Plates — 
Metol 2g 30 gr. 
Sodium sulphite 62.5 ¢ 2 oz. 
Hydrochinon 15.6¢ YZ oz. 
