sloughing of the emulsion may take place. Neutralization of acid in the bath invariably
causes certain kinds of stains on the radiographs. A good rule to follow is to change the
fixing bath when fresh developer is made, if the fixer tank is twice as large as the
developer tank and proper temperatures are maintained. When exceptionally high
temperatures prevail, the fixing bath should be changed twice during the life of the
developer. This assures maximum hardening of the emulsion and freedom from "hot
c. When the volume of the fixing solution is the same as that of the developing
solution, the fixing solution should be changed twice during the life of the developer to
ensure satisfactory clearing and hardening of the emulsion. Table 3-1 is a guide for
determining the clearing time, fixing time, and exhaustion point.
NUMBER OF 14 X 17
INCH FILMS FIXED
* Make new fixing solution before processing more film.
Table 3-1. Life of five gallons of unreplenished fixing solution in a single tank
at temperature range 60 to 75F.
3-29. SINGLE-TANK FIXER REPLENISHMENT
A fixing solution gradually loses its acidity because of the carryover of the
alkaline developer by the film. It also becomes diluted by water carried over from the
rinse bath. Consequently, its hardening properties and fixing rate are gradually
affected. The exhaustion of the thiosulfate reduces its ability to dissolve silver salts.
The loss in function of the fixing solution can in some measure be restored by
a. Advantages of Replenishment. By using the replenishment system, fixing
time may be kept to a minimum. In the first half of the life of the solution, the clearing
and fixing time may be kept relatively constant; in the latter half, the fixing time is slowly
increased to its exhaustion limit.
b. Method of Replenishment. In replenishing a five-gallon tank of fixing
solution, two quarts of solutions are removed and replaced by two quarts of fixer
replenisher solution. This solution is made by mixing the amount of chemical normally
used for one gallon of fixing solution with 2-1/2 quarts of water instead of one gallon.
This solution, therefore, is highly concentrated. If desired, the amount of chemical