Overview
EN ISO 19403-3:2024 - Paints and varnishes - Wettability - Part 3 specifies an optical test method for measuring the surface tension of liquids using the pendant drop method. Intended primarily for characterization of liquid coating materials, the standard defines the measurement principle (Young–Laplace analysis of a hanging drop), required apparatus and materials, sampling references and key evaluation criteria. It replaces the 2020 edition and includes annexes on density, the Worthington number and interlaboratory test details.
Key Topics
- Measurement principle: Determination of surface tension from the shape of a pendant drop via the Young–Laplace equation.
- Apparatus: Use of a state‑of‑the‑art drop contour analysis system with digital image capture and analysis, an optical system and a dosing unit (micro‑syringe).
- Needle requirements: Outside diameter of needles typically in the 0.5 mm to 2.5 mm range; selection depends on the ratio of surface tension to density difference (σ/Δρ).
- Sampling and density: Sampling per ISO 15528; density determination referenced to ISO 2811 parts 1–4 (pycnometer, plummet, oscillation, pressure cup methods).
- Applicability limits: The method is suitable for most liquid coatings but restrictions can apply for non‑Newtonian fluids (see ISO 3219‑1:2021 definition).
- Evaluation and quality: Standard includes precision data (repeatability and reproducibility), test reporting requirements and informative annexes (density, Worthington number, interlaboratory results).
Applications
EN ISO 19403-3:2024 is used by:
- Coatings formulators and R&D teams for characterizing surface tension during product development.
- Quality control laboratories verifying batch‑to‑batch consistency of liquid paints, varnishes and related formulations.
- Instrument manufacturers and labs validating drop contour analysis systems and test procedures.
- Academic and industrial researchers studying wettability, adhesion, spreading and surface energy components of coating materials.
Practical benefits include improved control of wetting, spreading and adhesion performance in coating processes and compatibility testing for substrates and additives.
Related Standards
- ISO 19403-1:2022 - Vocabulary and general principles (series overview)
- ISO 19403-4 / ISO 19403-5 - Methods for polar/disperse surface tension fractions
- ISO 2811 (Parts 1–4) - Density determination for paints and varnishes
- ISO 15528 - Sampling of paints and varnishes
- EN 14370, ISO 1409 - Other surface tension methods
Keywords: EN ISO 19403-3:2024, pendant drop method, surface tension, paints and varnishes, wettability, drop contour analysis, Worthington number.