Overview
ISO 15184:2020 - Paints and varnishes: Determination of film hardness by pencil test - specifies a rapid, practical method to assess the surface (film) hardness of coatings by pushing pencils of known hardness over the film. The method applies to a single coating or the upper layer of a multi‑coat system on smooth surfaces. ISO 15184:2020 is intended for relative rating of coated panels (not for precise cross‑product comparisons).
Key topics and requirements
- Principle: A pencil lead with defined geometry is pushed across the coating at a 45° angle with a force of (7.35 ± 0.15) N. The hardest pencil that does not cause visible marking defines the pencil hardness.
- Apparatus: A metal block test instrument with wheels, an inclined pencil holder (45°), a leveling device and calibrated force. A standard set of wooden pencils from 9B to 9H (B → softer, H → harder) is used.
- Pencil preparation: Special sharpener that removes wood only, abrasive paper (No. 400) to flatten the tip to a smooth circular cross‑section.
- Test conditions: Default environment (23 ± 2) °C and (50 ± 5) % RH; condition panels for at least 16 h prior to testing.
- Specimen preparation: Use representative sampling (ISO 15528), standard panels and substrates (ISO 1514), and measure dry film thickness per ISO 2808.
- Procedure essentials:
- Position instrument horizontally, apply pencil and push at constant slow speed.
- Inspect after 30 s (clean pencil fragments with an inert solvent if required).
- Repeat to bracket the hardness; perform duplicate tests (discard and repeat if results differ by more than one hardness unit).
- Defect types: Plastic deformation (indentation), cohesive fracture (visible scratch with material removed), or combination.
- Limitations: Applicable only to smooth surfaces; not suitable for absolute comparisons across different coating types. No precision data are provided in the standard.
Applications and users
ISO 15184:2020 is used for quick, practical evaluation of coating hardness, useful in:
- Quality control and production checks for paint, varnish and related products
- R&D and formulation screening to detect significant differences in surface hardness
- Test laboratories and specifiers verifying topcoat resistance to marking
Primary users include coating manufacturers, independent test labs, QC engineers, materials scientists and specification writers.
Related standards
Relevant normative references in ISO 15184:2020:
- ISO 1513 - Examination and preparation of test samples
- ISO 1514 - Standard panels for testing
- ISO 2808 - Determination of film thickness
- ISO 4618 - Terms and definitions for paints and varnishes
- ISO 15528 - Sampling for paints and raw materials
Keywords: ISO 15184:2020, pencil hardness, film hardness, paints and varnishes, pencil test, coating hardness test, surface hardness, paint film.