Open packages of photographic film should be stored at what humidity range?

• A. 20-40 percent
• B. 60-80 percent
• C. 40-60 percent
• D. 0-20 percent

Answer: (C)

Open packages of photographic film are most safely stored at a relative humidity that keeps the gelatin emulsion stable and minimizes both moisture-related damage and static buildup. A range around 40–60% RH provides that balance: it isn’t so dry that the film becomes brittle and prone to cracking or static discharge, and it isn’t so humid that the emulsion swells, becomes tacky, or supports mold and other moisture-driven degradation. Gelatin is hygroscopic, so it readily gains or loses moisture from the air; keeping humidity near mid-range prevents dimensional changes, sticking, or swelling while still limiting static electricity during handling. High humidity beyond this range increases the risk of mold and chemical interactions, while very low humidity increases static and dust attraction, both of which can mar the film. Therefore, 40–60% RH is the best choice.