How is film washing time measured?

• A. By external stopwatch measurement.
• B. Visually by observation only.
• C. Visually or with a flow meter w/ Water Line (+/- 10%), and done daily.
• D. By densitometer reading.

Answer: (C)

Measuring film washing time relies on ensuring the wash stage actually removes fixer residues rather than just guessing duration. The most reliable approach is to verify wash performance with a flow meter (showing the actual wash water delivery) and the Water Line reading, and to perform this check daily within a tolerance of about +/- 10%. This provides an objective, repeatable measure of how effectively the wash is functioning, since washing effectiveness depends on both contact time and adequate water flow. Visual verification can catch obvious issues like murky rinse water or visible blockages, but it’s subjective and doesn’t quantify performance. A densitometer measures the film’s optical density, not how long or how well it was washed. Relying on a stopwatch alone tells you how long the wash lasted, but not whether the flow and rinse effectiveness meet standards.