Varnishes 
VARNISHES.—The increasing use of bromide and develop- 
ment papers instead of printing-out papers, and, in a minor 
degree, the general adoption of films by amateur workers, has 
rendered less obligatory the use of negative varnishes for the 
protection of the gelatine surface. In the case of celluloid 
films, it is obvious that the solvents used in the varnishes must 
not attack the celluloid; therefore, the aqueous varnishes are 
preferred, though they do not give so much protection as the 
others. Varnishes may be classified as “hot” and “cold” 
varnishes, the former being applied to a heated negative, 
while the latter may be applied to the cold negative. In the 
first case, the negatives should be warmed in front of a fire 
or over a gas or spirit burner until the glass is as hot as the 
back of the hand can comfortably bear. 
Hot VARNISHES.— 
Orange shellac 752g 576 gr. 
Gum sandarac 75g 576 gr. 
Alcohol, 96% 1000 ccm 16 oz. 
Castor oil 2 ccm 15 min. 
Allow the mixture to stand with frequent shaking until the 
resins have dissolved; then filter. There is frequently some 
trouble in clarifying varnishes, as the fine insoluble particles 
will not easily filter out. The remedy is to add about 2 per 
cent by weight of some inert powder, such as finely powdered 
pumice stone or tripoli, shake well, and filter. Another 
formula: 
Orange shellac 50 g 384 gr. 
Gum elemi I5¢g 115 gr. 
Alcohol 1000 ccm 16 oz. 
150 
