Processing in black-and-white

Exposed film or paper is taken from a light-tight container in a darkroom and subsequently immersed in trays containing aqueous solutions of developer, stop bath, and fixer in black-and-white photographic processing. The film or paper is ready to use after being washed in water and dried. The developer turns the silver halide that has been exposed to light into metallic silver. The stop bath is a mildly acidic solution that neutralises the alkaline developer solution and prevents the silver halide from further reduction. The fixer produces a soluble complex with the unexposed silver halide, which is then removed from the emulsion in the washing step along with different water-soluble salts, buffers, and halide ions. Film rolls are typically treated in closed canisters with various solutions poured to them.

Hazards to your health

Only a few generalisations can be drawn about the sorts of chemical risks in black-and-white photoprocessing due to the large variety of formulae used by various vendors and varying techniques of packing and combining photoprocessing chemicals. The most common health concern is the risk of contact dermatitis, which is caused by skin contact with developer solutions. Alkaline developer solutions normally contain hydroquinone, but they may also contain p-methylaminophenolsulphate (commonly known as Metol or KODAK ELON). Developers irritate the skin and eyes, and in sensitive people, they might trigger an allergic reaction. The most dangerous component in most stop baths is acetic acid. Although concentrated stop baths are very acidic and can cause skin and eye burns if they come into contact with the skin or eyes, working-strength solutions are normally mild to moderate skin and eye irritants. Photographic hypo (sodium thiosulphate) and different sulphite salts (e.g., sodium metabisulphite) are used in fixers, which pose a negligible health risk.

In addition to the potential for skin and eye irritation, gases or vapours released by various photoprocessing solutions can cause inhalation problems and contribute to unpleasant odours, especially in poorly ventilated settings. Some photochemicals (for example, fixers) can produce ammonia or sulphur dioxide as a result of the breakdown of ammonium or sulphite salts. The upper respiratory tract and eyes may be irritated by these fumes. Furthermore, the acetic acid released by stop baths can irritate the upper respiratory tract and eyes. These gases or vapours have an irritating impact that is concentration dependant and is usually only noticed at concentrations that exceed occupational exposure limits. However, due to a wide range of individual susceptibility, certain people (for example, those with pre-existing medical disorders like asthma) may be affected at concentrations below occupational exposure limits. Because of the chemical’s low odour threshold, some of these compounds may be identifiable by odour. Although a chemical’s odour does not always signal a health hazard, strong odours or smells that are intensifying may suggest that the ventilation system is insufficient and should be evaluated.

Management of risks

Understanding the potential health dangers of exposure and managing the risk to an acceptable level are the keys to working safely with photoprocessing chemicals. Reading and comprehending product labels and safety data sheets is the first step in recognising and controlling potential hazards.

In terms of darkroom safety, avoiding skin contact is crucial. Neoprene gloves are especially useful for reducing skin contact in locations where more concentrated solutions are encountered, such as mixing. Gloves should be thick enough to avoid tears and leaks, and they should be inspected and cleaned on a regular basis—preferably with a non-alkaline hand cleaner on both the exterior and inner surfaces. Barrier creams are not suited for use with photochemicals since they are not impermeable to all photochemicals and may contaminate processing solutions; in addition to gloves, tongs can be used to prevent skin contact. In the darkroom, a protective apron, smock, or lab coat should be worn, and work clothes should be laundered frequently. Goggles should also be worn, particularly in places where concentrated photochemicals are handled.

Processing of Color

There are several more intricate colour processes that also include the use of potentially harmful chemicals. The printing, photographic, and reproduction industries are covered in the chapter Color processing. In colour photoprocessing, as in black-and-white photoprocessing, preventing skin and eye contact and allowing proper airflow are critical.