Other Developer Components

Alkali. Both the stability and energy of developing solutions depend upon their alkalinity (pH) on the pH scale, 7 is neutral, numbers lower than 7 represent acids, and numbers above 7 represent alkalis). Thus an alkali may be added to function as an accelerator in the solution. In general, the more alkaline a developer solution is, the more active, but the shorter its life. Many developers, such as Dektol and D-72, contain an alkali (usually sodium carbonate) that has a buffering action — that is, it has the ability to maintain a fairly stable pH throughout the useful life of the developer. When the developing agent is overused, there is a relatively sudden weakening of developer power, and the developer is said to be exhausted. Borax is occasionally used as the alkali, as in the Kodak Ektanol developer. Sodium hydroxide (caustic soda) is of very high pH, and seldom used in print developers; one exception is Edwal G, a very active form-See pages 117-118 ula. < Use great caution if you handle sodium hydroxide.

Developing agents such as amidol require no addition of alkali to the solution; the reaction of sodium sulfite with the water creates appropriate pH for their activity. Amidol, in fact, is exceedingly sensitive to the presence of alkali and will quickly oxidize and become useless if the pH is too high. In order to extend its life in solution, citric acid (a buffer) is usually added. This lowers the active energy of the developer, thus requiring longer development time, but prolongs the life of the developer.

Preservative. Sodium sulfite is added to retard oxidation, and is an essential ingredient to preserve the life of stock solutions. With such high reduction-potential* developers as amidol, it also produces a

'Reductionpotential indicates a developer's activity. Hydroquinone has been given the arbitrary reduction potential of 1, metol is 20, and amidol 35 plus.

slight alkalinity (pH of about 8), which is more than sufficient to activate amidol.

Restrainer. This substance retards reduction of silver halides, and is useful in preventing fog caused by high-energy developers, prolonged developing times, or the age of the paper. Out-dated papers or papers exposed to heat or humidity are especially likely to exhibit fog, and added restrainer may be needed. Without restrainer, the developing agent may reduce some unexposed halide to metallic silver, thus causing an overall fog. With negatives, slight fog can be ignored, since it is "printed through" and thus does not affect image values. With prints, however, even minor fogging can cause high values that are visibly degraded and "depressed." (Most cases of degraded high Sec page 31 values I see, it should be noted, are caused by safelight fogging, <

which must be cured by reducing the safelight intensity or by more careful handling of the paper.)

Potassium bromide is the most common restrainer added to prevent fogging. However, adding excessive bromide tends to cause the print color to become greenish with some papers (although this can usually be neutralized by selenium toning). Benzotriazole (available as Kodak Anti-Fog No. 1) is another widely used restrainer. It is sometimes claimed that benzotriazole lessens the image contrast. It may slow the development somewhat, but I have not been aware of a loss of contrast using normal quantities; if anything, it appears to increase contrast by "clearing" the high values. Benzotriazole tends to give cold tones, shifting the image color toward the blue.

Kodak Dektol and Kodak Selectol-Soft

My basic print developer for a number of years has been Dektol, a metol/hydroquinone developer which is similar in action to the pub-Sce Appendix i,page 190 lished D-72 formula. < At standard dilution (1:2 or 1:3) it gives what

I consider to be normal contrast with moderate developing times See pages 95-101 (2-3 minutes). Using the development-factor method < I can dilute

Dektol stock solution with as much as 6 to 8 parts water, and still achieve rich print quality. With underdevelopment, however, Dektol tends to give muddy values and an unpleasantly warm print color.

Selectol-Soft (note that this is different from Selectol) is a low-contrast "surface" developer, similar in action to the old Ansco 120 formula which used only metol as the developing agent. With normal processing time, Selectol-Soft will favor the high values of the print

first, gradually building up the dark values as it penetrates into the emulsion. Given long development time (up to 8 or 10 minutes) it will approach the effect of Dektol in deep black areas, with a rich and neutral print color. I use it alone, or combine it with Dektol for Sec pages 93-95 more subtle contrast control. <

Temperature Effects

See Book 2, page 201

Figure 3-4. Lava, Mauna Loa, Hawaii, Hawaii |c. 1948). Lava rock is of quite low rctlcctancc, although some, like this, gives bright specular reflections. To emphasize the shapes and textures in sunlight 1 chose to place the shadows very low on the exposure scale and give very full development. Here the deep shadows were placed on Zone I, and N + 2 development was given. I used the camcra back tilt to gain maximum depth of field (see Book 1, Chapter 10).

The print is on Brovira Grade 3, although today I would probably use Seagull Grade 2.

The action of a developer solution responds [like most chemical reactions) to temperature change. Raising the temperature makes the action more rapid, so that less time is required for development; lowering the temperature retards the action, so that more time is needed. As with film development, < 68°F (20°C) has been selected as the standard print-processing temperature for a variety of reasons, including practical developing time and efficiency of solutions. For optimum processing, all solutions including the wash water should be as close to this temperature as feasible.

The change of activity caused by a temperature change can be represented by the temperature coefficient for the developing agent. In a formula containing only one developing agent, a single temperature coefficient applies, and the relationship between temperature and developing time is easily determined. But in a developer that contains two or more agents, each may have a different coefficient, and it becomes more practical to experiment than to compute.

However, a change of temperature may affect not only the development time, but also the character of the developer, so that the print quality changes. For example, with metol the required development time varies uniformly with temperature change over a wide range, while the activity of hydroquinone is somewhat irregularly affected by temperature variations. Hydroquinone loses much of its activity at about 55°F, but has a very high activity at or above 75°F. Consequently, a metol/hydroquinone developer, producing normal effects at 68°F, gives somewhat softer effects as the temperature is lowered and the activity of the hydroquinone is thereby diminished; more vigorous effects occur as the temperature is raised and the hydroquinone becomes more active. Roughly speaking, a cold metol/ hydroquinone developer (about 50°-55°F; 10°-12°C) acts as though it were mostly metol. A certain amount of control is possible through variations in the temperature of a metol/hydroquinone developer, but the results should be judged on the basis of color as well as contrast. I became well aware of this effect while trying to get good prints in a chilly darkroom during cold winters in Yosemite!

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