(2) The chief purpose of the washing done in tank five is to remove the bulk
of the residual fixing solution and silver salts. Therefore, the water soon becomes
charged with these chemicals and should be discarded when 160 14- by 17-inch films
have been washed. Since the rotation of fixing and washing tanks is necessary to
conserve water, tank five is removed, the old wash water is discarded, and tank five is
filled with fresh water. Tank six is moved into the position of tank five and tank seven to
the tank 6 position. The former tank 5 containing fresh water is put in the number 7
position. This system of rotation is repeated each time tank five washes 160 14- by 17-
inch films in number five position.
PROCESSING AT 75 to 90F
a. The sequence of processing steps is the same as the one just described
except for the use of the specially treated developing and rinse bath solutions (Table
4-3). Time and temperature processing is accomplished by reference to Table 4-4. To
ensure emulsion stability when processing at these higher temperatures, 50 ounces of
sulfate is added to the developing solution. The rinse bath is replaced by a hardener
solution made according to the following formula. Any quantity may be mixed, so long
Potassium chrome alum
Sodium sulfate (desiccated)
2 1/2 pounds.
or Sodium sulfate (crystalline)
5 pounds, 10 ounces.
b. Development of the film in the temperature range of 75 to 90F ordinarily
would proceed at too rapid a rate for adequate control. Sodium sulfate, therefore, is
added to slow down the activity of the developer to more controllable limits. Be sure
that any replenisher added to the developer contains sodium sulfate in the quantity of
50 ounces per five gallons of prepared replenisher solution. The hardener bath used
after development serves to harden the emulsion so that the balance of the processing
procedure can be carried out without the emulsion becoming too soft or melting before
the final washing step.