Overview
EN ISO 14680-3:2006 - Paints and varnishes: Determination of pigment content - Part 3: Filtration method (ISO 14680-3:2000) specifies a standardized filtration procedure to determine the pigment (and other solid) content of coating materials. The method coagulates pigment with a methanolic potassium hydroxide solution, filters the solids on a pre-weighed filter crucible containing a bed of filtering aid, dries and weighs the residue, and calculates pigment content by mass percentage.
Key topics and technical requirements
- Scope and applicability
- Applicable to paints and varnishes that tolerate KOH-induced coagulation (particularly useful for coatings containing carbon black, very finely divided SiO2, TiO2, organic pigments or polymer dispersions).
- Not generally suitable for many water-dilutable paints (whole binder may coagulate).
- Principle
- Dilute sample with suitable organic solvent, add methanolic KOH (c = 1 mol/L) to coagulate solids, filter through a glass filter crucible with filtering aid, dry at 105 ± 2 °C, and weigh residue.
- Required apparatus and materials
- G3 glass filter crucible (pore size 15–40 µm) with a bed of filtering aid (e.g., diatomaceous earth)
- 50 ml wide-neck conical flask with PTFE stopper, suction flask and adapter, measuring cylinder, 5 ml safety pipette
- Drying oven with forced horizontal ventilation capable of 105 ± 2 °C; analytical balance to 0.001 g; desiccator
- Reagents: methanol (analytical grade), methanolic KOH (1 mol/L), suitable organic solvent
- Test procedure essentials
- Prepare and weigh filter crucible with filtering aid (10 g suspended, dried 1 h at 105 °C)
- Duplicate determinations: weigh 1–2 g test portion, add 20 ml organic solvent, add 1.5 ml methanolic KOH, wait 5 min, filter, rinse, wash solids with methanol, dry to constant mass and weigh
- Calculate pigment content: (m3 − m1) / m2 × 100 (m1 = crucible mass; m2 = test portion mass; m3 = crucible + solids mass)
- Precision
- Repeatability (r): 0.5% (absolute) for duplicates by one operator in one lab
- Reproducibility (R): 1% (absolute) between laboratories
- Reporting
- Include product identity, reference to ISO 14680-3, solvent used, individual and mean results, deviations, and test date
Applications and users
- Who uses it
- Laboratory analysts, quality control technicians, paint formulators, raw material suppliers, R&D teams, and conformity assessment bodies in the coatings industry.
- Practical uses
- Routine QC of pigment and filler loading in paints and varnishes
- Verification of batch composition, troubleshooting coating performance issues linked to pigment content (opacity, tint strength, rheology)
- Comparative testing where centrifuge or ashing methods are unsuitable
Related standards
Keywords: EN ISO 14680-3:2006, pigment content, filtration method, paints and varnishes, methanolic potassium hydroxide, filtering aid, filter crucible, precision, repeatability, reproducibility.