This section contains brief answers to practical questions about photochemistry—details on each topic can be found in the individual articles in this reference guide.
Is there anything else I can use instead of sodium sulfite if I don't have any on hand?
Yes, but with a weight adjustment and, as a rule, a 50% increase in the amount of alkali in the formula. Potassium metabisulfite and sodium bisulfite are viable substitutes, but they are acidic rather than neutral, so without adjusting the alkali content, the developer’s balance will be disrupted. Detailed conversion factors can be found in the article “Interchangeability of Reagents.”
Why does the developer become cloudy in the winter, or why does a sediment form in the bottle?
Below +5°C, solutions with a high salt content are at risk of partial crystallization, and at subzero temperatures, this applies to almost any liquid photochemical solution. You can salvage the solution by gently warming it in warm water (50–55°C), shaking it repeatedly, and then slowly cooling it. For a detailed step-by-step procedure, see the article “Solutions in Winter.”
Is it true that Rodinal works well for push processing?
No, that’s a common misconception. Rodinal is a moderately equalizing developer with fine grain, but it’s not well-suited for push processing or for expired, veiled film. For push processing, it’s better to use “Microphen,” AKFF, or X-TOL, and for expired film, use potassium bromide-based developers such as ST-2. For more details, see the article “A Few Things About Rodinal.”
Why is benzotriazole added to some developers?
Benzotriazole is a strong anti-haze agent used when there is not enough standard potassium bromide in the developer to suppress haze (most often on expired film). But there is a downside: an excessive concentration significantly reduces the photosensitivity of the photographic material, so the exposure is usually increased by 20–50%. For details and exact proportions, see the article “Anti-haze Agents.”
How can I reduce the graininess of a negative and a print?
Grain is determined by dozens of factors—from the film’s sensitivity and freshness to the precision of the developer and the intensity of the lighting during printing. There is no one-size-fits-all solution, but you can systematically address the main causes: shoot on fresh, low-sensitivity film, focus precisely, avoid over-development, and use an enlarger with diffused (matte) light. For a complete list of causes and recommendations, see the article “Combating Grain.”