Overview - ISO 2811-4:2011 (Pressure cup method)
ISO 2811-4:2011 is an International Standard that specifies the pressure cup method for determining the density of paints, varnishes and related products. The method is designed for aerated products (for example emulsion paints that trap small air bubbles) and uses a screw-driven piston in a cylindrical pressure cup to compress or dissolve entrapped air before measuring mass and volume. The method is not suitable for textured paints containing coarse particles.
Key topics and technical requirements
- Principle: Compress the sample in a calibrated cylinder to remove or compress entrapped air; calculate density from mass and calibrated volume.
- Apparatus:
- Pressure cup with screw-driven piston and pressure‑release cap; calibration collar stops piston at a closed volume of 100 cm³.
- Pressure-release set to about (1.0 ± 0.1) MPa (10 bar) so excess liquid escapes when full pressure is reached.
- Balance accurate to 10 mg, thermometer accurate to 0.2 °C, and a temperature-controlled chamber.
- Temperature control: Carry out the test at (23.0 ± 0.5) °C (other agreed reference temperatures can be used); sample and cup must be conditioned and stable within ±0.5 °C.
- Sampling and sample preparation: Follow ISO 15528 and ISO 1513 for representative sampling and preparation.
- Procedure: Single determination on a fresh sample - weigh empty cup (m1), fill and compress, weigh filled cup (m2); clean and recalibrate periodically.
- Calculation: Density ρ (g/cm³) = (m2 − m1) / Vt where Vt is the calibrated cup volume at test temperature (see Annex A).
- Calibration and corrections: Annex A covers cup calibration using air-free water (ISO 3696). Annex B gives thermal expansion corrections (stainless steel γ ≈ 48×10⁻⁶ °C⁻¹) and formulas to adjust density between temperatures.
- Precision: Repeatability limit r = 0.005 g/cm³. No reproducibility data currently available.
- Reporting: Test report must identify product, cup serial number, test temperature, result (rounded to 0.001 g/cm³), deviations and anomalies.
Applications and users
This standard is used for:
- Quality control in paint manufacturing and filling operations (density is critical for filling-machine control, formulation and batch consistency).
- Laboratory testing and product specification verification for emulsion and aerated paints.
- Suppliers, third‑party test labs, R&D teams and regulatory bodies that need reproducible density measurements for paints and varnishes.
Keywords: ISO 2811-4:2011, pressure cup method, density measurement, paints and varnishes, aerated paints, emulsion paints, calibration, temperature control, quality control.
Related standards
- ISO 2811 series (Part 1: Pyknometer, Part 2: Immersed body, Part 3: Oscillation)
- ISO 1513 - sample preparation
- ISO 15528 - sampling
- ISO 3696 - water for analytical laboratory use