Basic Photography Course

CHAPTER 9

CHEMICAL MIXING

When light-sensitive emulsions are used, photog-

raphy is essentially a chemical process. You depend
upon the chemical process to produce visible and
permanent images. An important requirement for
optimum photographic processing is the careful and
correct preparation of photographic solutions. Improper

mixing of chemicals or contamination during mixing
can have far-reaching effects on operations, quality,
production, and mission accomplishment in the imaging
facilities of the Navy. It is often difficult to determine
the cause of poor quality when improper chemical

mixing is at fault, and the need for discarding incorrectly

prepared or contaminated solutions cuts down on
production and wastes money.

The main function of the darkroom portion of the

photographic process is to develop film and produce
prints, and this requires photographic chemistry. It may
be your job to ensure that all chemicals needed are

mixed and checked for quality. "This is a responsibility
that you cannot take lightly." A solution that is mixed

improperly may cause an entire mission to be lost. You
must use the utmost precautions when mixing, checking,
or analyzing the photographic solutions used in your lab.

PHOTOGRAPHIC CHEMICAL AND

SOLUTION STORAGE

When you receive chemicals in your imaging

facility, the cartons, packages, or containers should be
dated to show either the date received or the date
shipped. This helps provide proper stock rotation and
systematic control of chemical usage. Chemicals should

be issued from the storeroom on a first-in-first-out

(FIFO) basis.

Unmixed chemicals should be stored in their

original, unopened containers in a cool, dry,
well-ventilated storage area where the temperature is
maintained at or about 75°F with a relative humidity of
about 40 percent.

Prepared solutions, like dry chemicals, also must be

protected from adverse conditions, especially oxidation
a n d c o n t a m i n a t i o n . W h e n t h e f o l l o w i n g
recommendations are adhered to, most "unused"

solutions stay in good condition for a reasonable period
of time:

Small amounts of replenisher and stock solutions

are best kept in stoppered or screw-cap bottles. Glass
bottles are best for developer and developer replenisher.
Screw caps must be free of corrosion, foreign particles,
cardboard inserts, and be airtight. Never interchange
bottle tops from one bottle to another. A cap-to-bottle
color or number code is suggested.

When large bottles are used to store solutions, the

air space in the bottle is increased each time the solution
is removed. Since this increases the chance for
oxidation, store solutions in small bottles instead. The
entire contents of a small bottle can then be used at one
time. However, a small air space should be left even in
small bottles. This allows for varying solution volume
due to temperature changes and keeps the cap from
loosening or the bottle from bursting.

When tanks are used for the storage of large

volumes of solutions, they should have floating lids to
protect the solutions from aerial oxidation Dust covers
also should be used to cover the top of the tank. The tank,
the lid, and the cap should be coded in such a way that
they are reassembled with the correct parts.

Always follow the storage and capacity

recommendations of the manufacturer. They are
packaged with the chemicals. Do not use chemicals that
have been in storage too long.

Before you use any solution, no matter how long

it has been mixed or in storage, check it for
discoloration. Each solution has its own "signature" or
characteristic appearance; and any change from normal
may be a sign that it will produce unsatisfactory results.
Check both sides and the bottom of the tank for
precipitates. If there are any, carefully stir the solution
to redissolve them. When you are unsure of the quality
of the solution, discard it.

Most photo-processing chemical formulations are

based on both their photographic qualities and their
chemical stability or keeping qualities, both on the shelf
before mixing and as prepared solutions. After
long-term storage, chemicals may lose some of their
chemical activity.

9-1

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Basic Photography Course

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DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> CHAPTER 9 CHEMICAL MIXING When light-sensitive emulsions are used, photog- raphy is essentially a chemical process. You depend upon the chemical process to produce visible and permanent images. An important requirement for optimum photographic processing is the careful and correct preparation of photographic solutions. Improper mixing of chemicals or contamination during mixing can have far-reaching effects on operations, quality, production, and mission accomplishment in the imaging facilities of the Navy. It is often difficult to determine the cause of poor quality when improper chemical mixing is at fault, and the need for discarding incorrectly prepared or contaminated solutions cuts down on production and wastes money. The main function of the darkroom portion of the photographic process is to develop film and produce prints, and this requires photographic chemistry. It may be your job to ensure that all chemicals needed are mixed and checked for quality. "This is a responsibility that you cannot take lightly." A solution that is mixed improperly may cause an entire mission to be lost. You must use the utmost precautions when mixing, checking, or analyzing the photographic solutions used in your lab. PHOTOGRAPHIC CHEMICAL AND SOLUTION STORAGE When you receive chemicals in your imaging facility, the cartons, packages, or containers should be dated to show either the date received or the date shipped. This helps provide proper stock rotation and systematic control of chemical usage. Chemicals should be issued from the storeroom on a first-in-first-out (FIFO) basis. Unmixed chemicals should be stored in their original, unopened containers in a cool, dry, well-ventilated storage area where the temperature is maintained at or about 75°F with a relative humidity of about 40 percent. Prepared solutions, like dry chemicals, also must be protected from adverse conditions, especially oxidation a n d c o n t a m i n a t i o n . W h e n t h e f o l l o w i n g recommendations are adhered to, most "unused" solutions stay in good condition for a reasonable period of time: Small amounts of replenisher and stock solutions are best kept in stoppered or screw-cap bottles. Glass bottles are best for developer and developer replenisher. Screw caps must be free of corrosion, foreign particles, cardboard inserts, and be airtight. Never interchange bottle tops from one bottle to another. A cap-to-bottle color or number code is suggested. When large bottles are used to store solutions, the air space in the bottle is increased each time the solution is removed. Since this increases the chance for oxidation, store solutions in small bottles instead. The entire contents of a small bottle can then be used at one time. However, a small air space should be left even in small bottles. This allows for varying solution volume due to temperature changes and keeps the cap from loosening or the bottle from bursting. When tanks are used for the storage of large volumes of solutions, they should have floating lids to protect the solutions from aerial oxidation Dust covers also should be used to cover the top of the tank. The tank, the lid, and the cap should be coded in such a way that they are reassembled with the correct parts. Always follow the storage and capacity recommendations of the manufacturer. They are packaged with the chemicals. Do not use chemicals that have been in storage too long. Before you use any solution, no matter how long it has been mixed or in storage, check it for discoloration. Each solution has its own "signature" or characteristic appearance; and any change from normal may be a sign that it will produce unsatisfactory results. Check both sides and the bottom of the tank for precipitates. If there are any, carefully stir the solution to redissolve them. When you are unsure of the quality of the solution, discard it. Most photo-processing chemical formulations are based on both their photographic qualities and their chemical stability or keeping qualities, both on the shelf before mixing and as prepared solutions. After long-term storage, chemicals may lose some of their chemical activity. 9-1 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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