LESSON 3
its complete dependence on the above, is a predictable result.
When
effective quality control procedures are being practiced, chemical analysis
is often used to check all chemistry solutions before and after use.
To
keep chemistry up to prescribed standards and to locate or isolate causes of
imperfect processing results caused by faulty or defective chemistry, good
quality control procedures are essential.
Furthermore, these procedures
permit the determination of proper replenishment formulas and rates to
promote economy in the consumption of chemicals.
Quality control at this
point guarantees that solutions are properly prepared, used, and discarded.
3. Evidence of developer exhaustion.
The function of a developer is to
effect a chemical change in the sensitized materials passed through it. It
is apparent that the condition of the developing solution itself must change
with use.
a. Since developer is often used more than once, in particular when
tank development is employed, it is important to know what changes to
expect, how these changes affect the function of the solution, and what can
be done to prevent them or to compensate for them. The major factors which
affect the performance of the developer are as follows:
(1) Loss of volume through evaporation and carryout.
(2) Loss of activity of components
due
to
chemical
reaction
(development and aerial oxidation).
(3) Loss of development potential because of an increase of bromide
content.
(4) Changes in physical content due to foreign matter, dirt, gelatin,
etc. entering the solution.
b. A good replenishment program attempts to replace used up or carried
out components and to dilute those which have increased.
It tries to
maintain the activity of the developer to approximate that of a fresh
solution or at some point after the peak of freshness has been removed.
Some technicians "ripen" solutions before starting their replenishment
program. To ripen a solution, process several sheets of fogged photographic
material in the developer solution to reduce the developer from a completely
fresh state to a partially used state where it is more stable.
c. Principles of replenishment.
It is possible for a developing
solution to become exhausted to the point that processing for a normal
length of time will produce no density except possibly in the most heavily
exposed areas. Such a developer
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