When light-sensitive emulsions are used, photography 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 75F with a relative humidity of about 40 percent.

Prepared solutions, like dry chemicals, also must be protected from adverse conditions, especially oxidation and contamination. When the following 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.

MIXING, TESTING, AND STORING EQUIPMENT

The type of material, used for photographic chemical mixing, solution testing, storing, as well as film-handling equipment, must be considered before mixing chemicals. Materials commonly used in the construction of this equipment are Type 316 stainless steel, polyethylene, and glass. Related equipment, such as solution transfer lines, mixer shafts, impellers, and machine parts, are also made of these same materials.

Some metals are not suitable for use with photo solutions. Serious chemical fog and developer changes can be caused by tin, copper, brass, and bronze. Aluminum, lead, nickel, zinc, galvanized iron, and Monel, when used with developers and fixers, can be harmful to films and papers. When these metals are used, silver thiosulfate from the used fixer may stick to them. Even when the utensils are washed after being in the fixer, enough silver thiosulfate can be transferred to the developer in the next processing or mixing run to cause stain, fog, or changes to image tone.

Wooden paddles and other absorbent materials must not be used with photographic solutions. Once they have been used, it is almost impossible to wash them clean of absorbed chemicals.