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HANDBOOK OF PHOTOGRAPHY 



controlled by the balance of the amounts of the three stock solutions used in the 

 individual batch and by the dilution of the combination. Negatives with such 

 developers usually have a characteristic pyro stain, tending to give them a distinct 

 brownish tone. In extreme conditions this tone may be made heavy so that it will 

 still remain after the silver js bleached out. Under ordinary conditions it is much less 

 apparent, though it still plays a part in printing, tending to increase the effective 

 printing contrast due to its brownish color more than it increases the visual appearance 

 of contrast. One accustomed to using this type of negative is apt to be disappointed in 

 results from a negative of similar visual quality made with developers not leaving this 

 stain image, as the prints from the latter tend to be less contrasty. The difference 

 is not such that it is possible to say that one is fundamentally better than the other 

 type of negative as both yield good results in the hands of experienced users. 



No. 7 Pyro-soda ABC Formula 



Stock Solution A 



Sodium bisulphite(or potassium metabisulphite) 9.80 g. 



Pyro _. 60.0 g. 



Potassium bromide 1 . 10 g. 



Water to make 1 1. 



Stock Solution B 



Sodium sulphite (anhydrous) 105 g. 



Water to make 11. 



Stock Solution C 



Sodium carbonate (monohydrated) 85 g. 



Water to make 11. 



1 oz. 130 gr. 

 8 oz. 



64 gr. 

 1 gal. 



13 oz. 

 1 gal. 



10 oz. 



1 gal. 



The dilutions and proportions usually recommended are 1 part each of solutions 

 A, B, and C with 7 parts of water for tray development and 11 parts water for tank 

 work. With many negative materials the developing times at 65°F. will then lie 

 between 6 and 8 min. for the tray development and between 9 and 12 min. for the tank 

 concentration. 



The three-solution pyro-soda developer has been a favorite for years, but its 

 instability after mixing is a marked disadvantage. A metol-pyro formula has been 

 proposed to secure much greater stability. This also is prepared as three stock 

 solutions. 



