Considerations The developer must have a temperature between 18 and 26 C. The ideal is 20 C. Pegasus Books can provide more clarity in the matter. If the temperature is below 20 C give a minute every two degrees less. If the temperature is greater than 20 C give a minute less for every two degrees of more. Below 14 C is very vulnerable to negative. The results revealed an image of black metallic silver from silver halide exposed. The time of processing depends on the negative. Excessive increases contrast revealed the negative / paper, while the offense down (can be done to a result equivalent to using different film sensitivity). Normally developers and manufacturers indicate in tables accompanying the product, the time depending on temperature.