Overview
ISO 19403-7:2017 - Paints and varnishes - Wettability - Part 7 specifies a standardized, dynamic method to measure the roll-off angle (tilt-stage contact angle) of a liquid drop on a solid surface. The method records the inclination at which a drop begins to roll off and derives the advancing and receding contact angles during motion. This measurement is widely used to evaluate easy‑to‑clean, anti‑adherent and self‑cleaning coatings and surfaces.
Key topics and technical requirements
- Principle: A droplet is placed on the test surface; the sample is tilted at a constant speed until the drop rolls. The time‑resolved left and right three‑phase points produce advancing and receding angles and the roll‑off angle.
- Apparatus: A contact angle measuring system with a tilt stage (camera/image capture preferred) and a precision dosing unit for microlitre drops.
- Test liquids: Suggested liquids include water, di‑iodomethane, ethylene glycol, glycerol, hexadecane (see standard for full table). Water for tests should have surface tension ≥ 71.5 mN/m.
- Specimens & sampling: Representative, uncontaminated specimens; recommended minimum size of 10 cm × 10 cm. See Annex A for sampling/treatment guidance.
- Test conditions & conditioning: Standard atmosphere at (23 ± 2) °C and (50 ± 5) % RH. Panels conditioned for a minimum period at these conditions prior to testing.
- Measurement specifics: Position the dosing needle ~3–6 mm above the surface; align image baseline through three‑phase points; tip the specimen at constant speed. Roll‑off is defined when both three‑phase points move a specified distance (Δ ≥ 1 mm).
- Data & reporting: From dynamic measurements obtain roll‑off angle plus advancing and receding angles. The standard includes precision, influencing factors (Annex B), and required test‑report content.
Applications
- Evaluating easy‑to‑clean and anti‑adhesive coatings (paints, varnishes, protective layers).
- Quality control for surface treatments, hydrophobic or oleophobic finishes, and functional coatings (self‑cleaning, anti‑soiling).
- R&D for formulators optimizing surface energy, roughness and chemical homogeneity to control droplet mobility.
- Surface science research where dynamic wetting behaviour (hysteresis between advancing/receding angles) matters.
Who should use this standard
- Coatings and surface‑finish manufacturers
- QC/analytical laboratories performing wettability testing
- Material scientists and formulation chemists
- Test houses assessing product claims (self‑cleaning, anti‑soiling)
Related standards
Using ISO 19403-7:2017 ensures consistent, reproducible roll‑off angle testing for product development, certification and comparative performance assessment of coatings and surfaces.
Open preview (PDF)Paints and varnishes — Wettability — Part 7: Measurement of the contact angle on a tilt stage (roll-off angle)