Overview
ISO 18951-2:2022 - Imaging materials - Scratch resistance of photographic prints - Part 2: Sclerometer test method - specifies a standardized, low‑cost procedure to evaluate the scratch resistance of photographic prints using a handheld sclerometer. The method applies to unprotected prints as well as prints with coatings or laminates and is intended for comparative testing rather than defining pass/fail limits.
Key topics and technical requirements
- Test principle: A tungsten‑carbide stylus is drawn across the print at a controlled vertical load to induce indentation and scratch damage. The force at which specific damage appears is recorded as a critical load (Lc or Fc).
- Damage levels: Defined qualitatively as Level 0 (no damage) to Level 3 (rupture, delamination, ploughing). Critical loads for levels 1, 2 and 3 (Lc1, Lc2, Lc3) can be determined.
- Test device: Handheld pen‑like sclerometer with a spring‑loaded tungsten carbide tip; accessories (fixtures/trolleys) may be used to hold a fixed angle.
- Stylus selection: Standard spherical tips of 0.50 mm diameter; 1.00 mm tip allowed for very scratch‑sensitive materials.
- Load range: Typical spring ranges noted (e.g., 0–3 N, 0–10 N, 0–20/30 N) to produce variable forces.
- Sample requirements: Test targets may be color patches or representative prints; samples must be appropriately prepared and conditioned prior to testing.
- Evaluation: Visual assessment against reference samples is primary; quantitative measures can include scratch width at constant loads. Colorimetric or densitometric methods are generally not suitable for characterizing scratch damage.
- Reporting: Standard specifies required test parameters, procedures, test target descriptions and reporting items. The standard does not set acceptance limits - users define those based on application.
Practical applications and who uses it
- Print manufacturers and materials suppliers use ISO 18951-2 to compare coatings, laminates, inks and substrates for scratch resistance.
- Quality control and test laboratories adopt the sclerometer method for routine comparative performance testing.
- Photofinishers, print service providers and archival conservators use the results to guide handling, finishing (lamination), and packaging decisions.
- R&D teams use the method when developing more durable digital prints, protective coatings, and surface treatments.
Related standards
Keywords: ISO 18951-2:2022, sclerometer test, scratch resistance, photographic prints, imaging materials, critical load, tungsten carbide stylus, print durability.