ISO 2811-3:2023

Overview

ISO 2811-3:2023 - "Paints and varnishes - Determination of density - Part 3: Oscillation method" specifies a standardized laboratory method to determine the density of paints, varnishes and related products using an oscillator (glass or stainless-steel U-tube). The method is suitable for all matrices including paste-like coatings and, when a pressure‑resistant apparatus is used, aerosols. The standard emphasizes temperature control, sample preparation (including de‑aeration), apparatus calibration and reporting for reproducible density determination.

Key topics and requirements

• Measurement principle: Resonance frequency (period of oscillation) of a filled U‑tube varies with mass; frequency is converted to density using apparatus constants.
• Temperature control: Test temperature is normally (23.0 ± 0.5) °C; sample, tube and oscillator must be conditioned and maintained within ±0.5 °C.
• Sample preparation: Follow ISO 15528 and ISO 1513 for sampling and preparation. De‑aeration of samples is required where necessary to ensure reproducible results (notably waterborne matrices).
• Apparatus: U‑tube oscillator (models that display period T or directly display density), thermometer (±0.2 °C), temperature chamber, syringes for filling.
• Measurement procedure:
  • Clean and check apparatus (display should indicate air density).
  • Fill U‑tube per manufacturer's instructions, avoid air bubbles and close filler hole.
  • Take multiple readings: at least three period readings or density readings, with specified tolerances (period and density variation limits are given).
• Calibration and constants: Annex A describes determination of apparatus constants (A and B) using air and air‑free water; constants are valid only near the calibration temperature.
• Precision: Repeatability r = 0.001 g/cm3; reproducibility R = 0.002 g/cm3 for materials without entrapped air.
• Reporting: Report product ID, reference to ISO 2811-3:2023, apparatus model, test temperature, density (rounded to 0.001 g/cm3), deviations and anomalies.

Applications and users

ISO 2811-3:2023 is used for:

• Quality control and incoming/outgoing inspection in paint, varnish and coatings manufacturing.
• R&D and formulation labs monitoring density for batch consistency, solids content and filling behavior.
• Testing of paste-like coatings and, with proper apparatus, aerosol products.
• Independent testing laboratories and certification bodies requiring traceable density measurements.

Typical users: coating manufacturers, QC/analytical labs, instrument manufacturers (oscillators), aerosol producers, and standards/conformity assessment organizations.

Related standards

• ISO 2811 series (other parts for alternative density methods)
• ISO 15528 (sampling)
• ISO 1513 (sample examination/preparation)
• ISO 3696 (water purity for calibration)

Keywords: ISO 2811-3:2023, density determination, oscillation method, paints and varnishes, U-tube oscillator, de-aeration, temperature control, apparatus calibration, repeatability, reproducibility.