Overview
ISO 21545:2018 - Paints and varnishes - Determination of settling - specifies a laboratory method to measure short‑time settling of coating materials. The method is intended to quantify sediment that forms during short storage or handling intervals (for example, during transport or in an electro‑deposition bath) by measuring the volume of settled material in a measuring cylinder and expressing it as a percentage of total volume.
Key topics and technical requirements
- Scope: Determines short‑time settling of paints and varnishes; not intended as a long‑term shelf‑life test.
- Principle: Let a filled measuring cylinder stand at a specified (usually room) temperature for an agreed holding time; measure the settled sediment height/volume and report as % of total.
- Sampling & preparation: Take a representative sample per ISO 15528 and prepare/examine samples per ISO 1513. Stir samples if necessary before filling the cylinder.
- Apparatus: Ordinary lab glassware plus:
- Laboratory stirrer
- 100 ml (1 ml graduations) or 250 ml (2 ml graduations) measuring cylinder, accuracy class B in accordance with ISO 4788
- Time measuring device (reading accuracy 30 s)
- Test conditions: Carried out at room temperature (record actual temperature). Cylinder size and holding time shall be agreed and documented.
- Procedure: Clean and dry cylinder, fill to the specified volume mark (100 ml or 250 ml), cap, stand for agreed time, read sediment volume, calculate percentage, and report result.
- Reporting requirements: Test report must include product identification, reference to ISO 21545, test temperature, cylinder size, holding time, result (sediment volume %), deviations, unusual observations, and date.
- Precision: No precision data provided in the standard.
Applications and who uses it
- Quality control laboratories in paint and varnish manufacturing to monitor short‑term stability and transport performance.
- R&D and formulation teams assessing pigment/vehicle compatibility and anti‑settling measures.
- Process engineers evaluating conditions in electro‑deposition baths or handling processes where short‑term settling matters.
- Suppliers and testing laboratories requiring a standardized, reproducible short‑term settling test for specifications or batch release.
Related standards and references
- ISO 1513 - Examination and preparation of test samples
- ISO 15528 - Sampling of paints and varnishes
- ISO 4788 - Graduated measuring cylinders (laboratory glassware)
- ISO 4618 - Terms and definitions for paints and varnishes
- ASTM D869 - Alternative method for evaluating degree of settling (longer‑term / shelf‑life style test)
Keywords: ISO 21545:2018, paint settling, paints and varnishes, settling determination, measuring cylinder, short‑time settling, electro‑deposition bath, test procedure.