152 PHOTOGRAPHIC FACTS AND FORMULAS 
Glycerine 3ccm 23 min. 
Water 1000 ccm 16 oz. 
The method of making is as above. Or: 
Bleached shellac 150 B00 2a haa 
Alcohol 300 ccm 5. 1/3/02, 
Dissolve, and add: 
Ammonia 225 ccm 4 oz. 
Glycerine 7 ccm 54 min. 
Warm water 1000 ccm 16 oz. 
The above are particularly suitable for films. When using 
bleached shellac, it is essential to procure freshly bleached lac, 
or that which has been kept under water, as, when exposed to 
the air, this loses its solubility to a great extent. Dichlor- 
hydrin is an excellent solvent for bleached shellac, when 
warmed, but this varnish cannot be used for films, as it dis- 
solves the celluloid. 
An excellent varnish (Valenta) is made as follows: 
Gum dammar 75g 576 gr. 
or Gum mastic 60 g 460 gr. 
Carbon tetrachloride 1000 ccm 16 oz. 
If the mastic is used, it is necessary to heat to obtain perfect 
solution. Both varnishes give hard surfaces, which take 
retouching well. 
Epichlorhydrin and dichlorhydrin have also been recom- 
mended (Valenta) as solvents for varnishes, but have found 
little use. The following are suitable formulas: 
Copal 20 g 154 er. 
Epichlorhydrin 70 ccm 1 oz. 
Digest on a water bath until dissolved, and add: 
Alcohol 770 ccm 11 oz. 
Epichlorhydrin 160 ccm 4 oz. 
Then filter. This gives a very hard film that dries quickly, 
