What is the typical tolerance for film washing time measurement?

• A. +/- 5%
• B. +/- 10%
• C. +/- 15%
• D. +/- 20%

Answer: (B)

In radiographic film processing, washing time must reliably remove fixer residues without wasting water or risking damage from over-washing. The typical tolerance of plus or minus 10 percent reflects the real-world variability you see with wash water temperature, agitation, film load, and small differences in the wash cycle. This range ensures there is enough time for thorough washing so residues don’t affect image quality, while not being so tight that normal fluctuations trigger out-of-tolerance readings. For example, if the target wash time is 180 seconds, an acceptable range would be about 162 to 198 seconds. A tighter tolerance like ±5% is often impractical due to everyday process variability, while looser tolerances (±15% or ±20%) could allow enough chemical residue to cause image or emulsion effects.