LESSON 3
e. Procedures for replenishment.
With varying degrees of success,
depending upon the nature of the developer, the decrease in developer
activity with use can be partially overcome by increasing the development
time.
This procedure is available with instructions from the various
developer data sheets.
(1) A better procedure and one particularly valuable when large
quantities of solution are involved, is to compensate for the developer
exhaustion by periodically adding small amounts of replenisher solution.
Usually replenishers are such that, when used as recommended, the developer
activity is held approximately constant.
(2) The quantity of the developer solution carried out varies with
the processing conditions. Most replenisher formulas are balanced to suit
their major field use. For other conditions, adjustments may be necessary.
If, after replenisher has been added, the developer is still at a low
activity level, more replenisher should be added, even though it is
necessary to discard some developer.
However, if the developer tends to
gain in strength, when the replenisher added is just sufficient to replace
that carried out, dilute three or four parts of replenisher to one part of
water and add to the solution to keep the volume constant.
(3) Small volumes of developer, such as are used in hand-processing,
are best replenished by the addition of a definite quantity of replenisher
for each roll or sheet of film processed.
Ordinarily, constant developer
activity can be maintained by adding one ounce of replenisher for each 80
square inches of film.
This is equivalent to one 8x10 or four 4x5 sheet
film, one 120 roll film, or one 36-exposure roll of 35 mm film.
After
processing one roll of film (80 sq. in.), pour one ounce of replenisher
solution into the developer storage bottle.
Add enough of the used
developer solution to bring the bottle to original volume.
If original
volume is not attained, add unused developer solution or replenisher diluted
two parts with one part water to make up for the loss. Repeat for each roll
(80 sq. in.) developed.
(4) This is only one of the many ways that a developer can be
replenished.
It is impractical to replenish a developer indefinitely,
because the solution accumulates a silver sludge as well as particles of
dirt and gelatin which may adhere to the film surface. The developed film
should be examined carefully. If they show any indication of stain or fog,
the developer should be discarded.
(5) One of the best ways to monitor the activity of a developer is to
develop periodically a series of sensitometric strips as the solutions are
used. A sensitometric strip is a
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