Overview
ISO 18904:2000 - "Imaging materials - Processed films - Method for determining lubrication" specifies a non‑destructive test to detect the presence of a lubricant on processed photographic film. The method uses a simple inclined‑plane friction test in which a rider built around the round end of a common steel paper clip is allowed to slide on the film surface. The tangent of the inclination angle is reported as a paper‑clip friction coefficient, giving an indicator of whether post‑process lubrication is present. The test can be applied to both the emulsion and support sides and is intended primarily for film after processing.
Key topics and technical requirements
- Test principle: Classical inclined‑plane friction with a paper‑clip‑type slider; tangent(angle) = coefficient of friction.
- Friction slider: Inverted U‑shaped slider using the larger round end of a standard steel paper clip. Mass recommended between 50 g and 100 g and centre of gravity at least 25 mm below the clip end.
- Test rig: Smooth, hard inclined plane with clips to hold the film; calibrated to read tangent values in increments of 0.05 up to at least 0.50.
- Sample preparation: Typical samples ~150 mm long and up to 35 mm wide; avoid contamination from grease or gloves.
- Environmental conditions: Relative humidity 30–55%, temperature 20 °C ± 5 °C; samples conditioned for ~2 hours.
- Procedure: Place slider on film, adjust plane angle until slider just sustains initial motion; repeat at three spots and report the arithmetic mean.
- Interpretation & precision:
- Unlubricated film often yields coefficients > 0.40 (support side is more reliable).
- Well‑applied lubricants often give ≤ 0.15.
- Repeatability is typically within ±10% for a careful operator.
- The test detects presence of lubricant but does not fully characterize dynamic friction behavior or predict lubricant performance in specific applications.
Applications and users
- Practical uses:
- Quality control in photographic film processing to verify post‑process lubrication.
- Manufacturing verification for film producers and finishing houses.
- Archivists and conservators checking microfilm and projection prints for adequate lubrication to prevent abrasion and projection failures.
- Projection and microform labs monitoring lubricant application where mechanical transport or gate tensions can damage film.
- Primary users: film processors, labs performing acceptance testing, imaging QA engineers, conservation specialists, and technical staff in motion‑picture and microfilm operations.
Related standards (if applicable)
ISO 18904:2000 is part of the ISO 18900–18999 block for imaging materials. It replaced ISO 5769:1984. Related ISO documents in the same block address stability, storage and other physical tests for photographic materials (see ISO 18901, ISO 18903, ISO 18906, etc.). For implementation, consult the full ISO 18904:2000 text for figures, calibration details and reporting formats.
