Darkroom humidity should be maintained in which range?

• A. between 5 and 10%
• B. between 20 and 30%
• C. between 40 and 60%
• D. between 70 and 80%

Answer: (C)

Maintaining a moderate relative humidity in the darkroom is important to prevent static electricity during film handling. When the air is too dry, static discharges can occur as you move unprocessed film, creating sparking marks and attracting dust that can stick to the emulsion and ruin images. If the air is too moist, other issues can arise, but the key practical reason for this range is reducing static while keeping the environment safe for film and chemicals. The best range is between 40 and 60 percent relative humidity because it minimizes static buildup and avoids the problems that come with both overly dry and overly moist conditions. Humidity levels between 5 and 10 percent or 20 to 30 percent are too dry and promote static, while 70 to 80 percent is too humid and can cause other handling and processing concerns.