What processing error causes films to look milky and slowly darken over time?

The characteristic of films appearing milky and gradually darkening over time is primarily associated with insufficient fixing during the processing stage. A weak fixer solution fails to adequately remove the unexposed silver halide crystals from the film emulsion. As a result, those unreduced crystals continue to react to light, which may lead to a milky appearance. Over time, the remaining unexposed silver halides can further darken with prolonged exposure to light, resulting in a gradual darkening of the film.

In contrast, the other factors listed, such as an oxidized developer solution, cold wash water, or elevated developer temperature, do not specifically contribute to this milky appearance and gradual darkening in the same way. An oxidized developer affects the film's ability to develop properly, potentially leading to underexposure or poor density rather than a milky look. Cold or non-circulating wash water doesn't cause this effect either; instead, it may lead to inadequate clearing but doesn't specifically result in the particular milky look described. Lastly, developing films at above normal temperatures can enhance the developer's activity, usually leading to overdevelopment rather than the milky characteristic. Therefore, a weak fixer solution is the most relevant issue connected to films becoming mil