PEATE, BACKING 33 
Or; 
Nigrosine, spirit soluble 10¢g 77 gr. 
Pyroxyline 30 g 230 gr. 
Methyl alcohol 400 ccm 64 oz. 
Ether 600 ccm OY oz. 
Castor oil 60 ccm 460 min. 
Or: | 
Celluloid scraps 45 ¢ 350 gr. 
Nigrosine : 10g TI EE: 
Amy] acetate 250 ccm 4 oz. 
Acetone 750 ccm 1ioz. 
This takes some hours to dry. By replacing the amyl acetate 
with methyl alcohol, a much quicker drying mixture is 
obtained. These, like the asphalt backings, are sometimes 
difficult to remove, but friction with soap and water readily 
removes them. 
Brack Bacxinc.—For ordinary, non-colour-sensitive 
plates, the following may be used: 
Burnt sienna, paste 750 g 34 |b. 
Dextrine 63 g loz: 
Water 63 ccm 1 oz. 
Phenol (carbolic acid) 5 Cem 50 drops 
For panchromatic plates, use ivory sienna black instead of 
the burnt sienna. These pigments can be obtained from any 
colourman, ground in water. Mix the dextrine and water, 
heat until dissolved, and then work in the colour paste and 
the carbolic acid, which is merely added to prevent the stock 
from growing mouldy. 
CHREVETOTS BACKING.— 
White castile soap 60 g 46 er. 
Alcohol, 90° 1000 ccm 16 oz. 
Dissolve in a water bath and add: 
