158 PHOTOGRAPHIC FACTS AND FORMULAS 
Water 37.5 ccm 288 min. 
Hydrofluoric acid 37.5 ccm 288 min. 
Denatured alcohol to 1000 ccm 16 oz. 
Spread the solution with a brush or spill of paper, and allow 
to soak for about 5 minutes. Then try and strip the narrow 
cut edges; if these can be easily removed, the work may be 
proceeded with; if not, the plate should be left a little longer. 
When the film is loose, as shown by the above test, pour off 
the liquid carefully, taking care not to let the film slip. Pour 
on some of the above solution without the acid, leave for 2 or 
3 minutes, and then drain this off. Gently place a piece of 
smooth waxed paper or thin celluloid over the negative, and 
lightly squeegee into contact; on lifting the paper, the film 
will be removed with it, and can be transferred to another 
support. Great care must be taken in the use of the above 
solution, as it attacks the fingers and all glass. It is better 
either to make up the stock solution without the hydrofluoric 
acid and add this just before use, or to omit the acid alto- 
gether, and use instead: 
Sodium fluoride 30 g 230 gr. 
or Potassium fluoride 44¢ 337 gr. 
Add just before use: 
Nitric acid 75 ccm 576 min. 
If the gelatine skin is to be kept as a film, it should first be 
coated rather thickly with enamel collodion, made as follows: 
Pyroxyline 30 g 230 gr. 
Alcohol 500 ccm 8 oz. 
Ether 500 ccm 8 oz. 
Castor oil 20 ccm 154 min. 
Allow to dry thoroughly before applying the stripping fluid. 
In order to obviate the use of the fluorides, the following 
may also be used with success: 
Potassium carbonate 100 g 770 gr. 
