ISO 14680-3:2000

Overview

ISO 14680-3:2000 - Paints and varnishes - Determination of pigment content - Part 3: Filtration method - specifies a laboratory test for measuring the pigment (and other solid) content of coating materials by coagulating the solids with a methanolic potassium hydroxide solution and recovering them by filtration. The method is tailored to products containing carbon black, very finely divided silica or titanium dioxide, organic pigments or polymer dispersions. It is not suitable for many water-dilutable paints where the whole binder coagulates.

Key topics and technical requirements

• Principle: Dilute a test portion in a suitable organic solvent, add methanolic KOH to coagulate solids, filter through a glass filter crucible with a bed of filtering aid, dry and weigh the residue to calculate pigment content.
• Apparatus & materials:
  • Glass filter crucible (G3, 15–40 µm pore) with a bed of filtering aid (e.g., diatomaceous earth)
  • 50 ml wide‑neck conical flask with PTFE stopper, suction flask with adapter, drying oven with forced horizontal ventilation
  • Analytical balance (0.001 g), desiccator, methanol (analytical grade), 1 mol/L KOH in methanol
• Procedure essentials:
  • Prepare filter crucible by depositing and drying filtering aid.
  • Test in duplicate (1–2 g sample): add solvent, add 1.5 ml methanolic KOH, wait 5 minutes, filter, rinse, wash with methanol, dry to constant mass at 105 °C and weigh.
  • Calculate pigment content as percentage by mass from filter crucible and residue weights.
• Quality and precision:
  • Duplicate test acceptance: results must agree within 0.5% (relative) or repeat the test.
  • Repeatability (r): 0.5% (95% probability)
  • Reproducibility (R): 1% (95% probability)
• Safety note: Solvent vapors can form explosive mixtures; oven ventilation and solvent-handling precautions are required.
• Reporting: Include product identification, reference to ISO 14680-3, organic solvent used, individual and mean results, deviations, and test date.

Applications and who uses it

• Quality control and batch verification in paint, coatings and varnish manufacturing
• Analytical and R&D laboratories determining pigment load, extenders and solid content
• Technical specification and acceptance testing for suppliers and purchasers of coatings
• Regulatory or forensic labs assessing composition of coating samples

Keywords: ISO 14680-3:2000, pigment content, filtration method, paints and varnishes, potassium hydroxide coagulation, filter crucible, filtering aid, laboratory test, repeatability, reproducibility.

Related standards

• ISO 14680-1 - Centrifuge method (alternative for pigment content)
• ISO 14680-2 - Ashing method (alternative for pigment content)
• ISO 1513 - Examination and preparation of samples for testing
• ISO 15528 - Sampling of paints, varnishes and raw materials

This summary helps analysts and QC teams quickly understand the filtration method under ISO 14680-3:2000 and when to apply it versus centrifuge or ashing alternatives.