Processing for Permanence

Silver-Gelatin Films

Processing is one of the most important factors affecting the potential permanence of photographic records. The removal of residual processing chemicals, the exclusion of dirt contamination, and uniform drying are factors normally controlled by proper processing.

Processed film, for long-term storage or permanent records, must meet the requirements of ANSI/PIMA IT9.1-1992 (R1996) or ISO 18901.2 The ability to meet most of these requirements is controlled in film manufacture, but films must be fixed and washed adequately, whether given conventional or full-reversal processing, to meet residual thiosulfate requirements. Films processed without fixation, such as in halide- reversal processes and certain reversal processes with only redevelopment, may give a “visible, usable image,” but do not come under the scope of the long-term storage standards.

If fixing and washing are inadequate, thiosulfates or silver salts, or both, will be retained by the film. These can break down, especially under poor storage conditions, to produce yellow stain in clear areas and fading in areas containing image silver.

Fixing Baths

In the fixing step, undeveloped silver-halide crystals in the emulsion are converted to soluble silver compounds which can be washed away with water. The chemicals most commonly used for fixing are sodium or ammonium thiosulfate (commonly called “hypo”). The fixing bath may also contain other chemicals to maintain a desirable pH, provide hardening, stabilize the solution, protect the image from microscopic blemishes, etc.

For maximum washing efficiency, a non-hardening fixer followed by a non-oxidizing washing aid, such as Microfilm Clearing Bath and Replenisher should be used. (Call Solutek at 1-617-445-5335 to order CAT No. 414-24). Hypo eliminators containing oxidizing agents, such as peroxide, should be avoided. Oxidizing agents may promote image deterioration.

To make sure that there is enough time for the fixing reaction to be completed, specific recommendations for each type of film should be followed. Undeveloped silver halides are dissolved by the fixer as complex ions of silver and thiosulfate. As the silver content of the fixer increases with processing, the silver-thiosulfate complex becomes increasingly difficult to wash from the film. This can be avoided by frequent replacement or proper replenishment of the fixing bath or by in-line recirculating electrolytic recovery of silver from the fixer.

Recovery of silver from fixer is advisable for reasons of economics, conservation and ecology. There are three principal methods of silver recovery:18 metallic replacement, electrolytic and sulfide precipitation. For additional information, refer to Kodak Publication J-212.23

Washing

Adequate washing is essential to the permanence of silver-gelatin microfilm. After all undeveloped silver halide is converted, the emulsion is still saturated with fixing bath and some dissolved silver compounds. If these are not removed by washing, they will slowly decompose and attack the image, causing discoloration and fading.

The effect is accelerated greatly by high humidity and temperature. The smaller the grain size of the image, the greater this reaction is. Microfilms, being very fine grained, are very sensitive to this effect.

For good washing, a rapid flow of fresh water should be used. The water should be filtered to remove dirt particles. To improve washing, countercurrent and spray systems are frequently used in processing-machine construction. Washing efficiency decreases rapidly with decreased temperature and is very low

at temperatures below 16°C (60°F). High wash-water temperatures produce the most efficient washing, but emulsion reticulation can result if the wash-water temperature is too high and not kept close to that of the other processing solutions. In some cases, extremely soft water can also cause reticulation. In the case of contained chemical kits such as the Kodak Miniprocessor, the manufacturer's recommended film processing capacity should not be exceeded.

D-31 June 2002

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Kodak D-31 manual Processing for Permanence, Silver-Gelatin Films, Fixing Baths, Washing
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D-31 specifications

Kodak D-31 is a color negative developer that has garnered attention for its unique set of features tailored to meet the demands of both professionals and enthusiasts in the field of photography. Designed primarily for use with color negative films, Kodak D-31 is known for delivering impressive results in terms of color reproduction, contrast, and image sharpness.

One of the standout characteristics of Kodak D-31 is its flexibility in processing various types of color negative films. This developer can be used for a range of ISO sensitivity ratings, making it versatile for different photographic situations. Whether capturing landscapes, portraits, or street photography, D-31 ensures that the vibrant colors and subtle tones of each scene are accurately represented.

The technology behind Kodak D-31 incorporates a balanced mixture of color-forming agents and stabilizers that contribute to its reliability. The developer uses a carefully controlled chemical composition that ensures consistent performance with minimal grain, which is a critical factor for photographers who demand high-quality prints. The result is images that display fine detail and smooth transitions in color, which can be particularly important in post-processing and printing.

Kodak D-31 is designed for easy use, featuring a simple processing workflow that can be followed even by those new to film development. The Developer can be used with standard tanks and is compatible with both manual and automatic processing equipment. This ease of use makes D-31 an excellent choice for educational settings and home darkrooms, as it allows users to focus more on the art of photography rather than the technicalities of the developing process.

An additional advantage of Kodak D-31 is its ability to deliver consistent results across different batches, which is essential for those looking to maintain a cohesive portfolio. Photographers can rest assured that each roll developed will yield similar results, thanks to the high degree of control in the chemical composition and the assurance of quality that Kodak has provided for decades.

In summary, Kodak D-31 stands out as a reliable, versatile, and high-performance color negative developer that is well-suited for a variety of photographic applications. Its thoughtful formulation offers photographers the ability to capture and reproduce color with precision, making it a preferred choice for both hobbyists and seasoned professionals alike. With its blend of technology and ease of use, D-31 continues to be a valuable tool for anyone looking to explore the rich world of color film photography.
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