Overview
ISO 6713:1984 - Paints and varnishes: Preparation of acid extracts from paints in liquid or powder form - specifies laboratory procedures to prepare acid extracts used for determining soluble metals in paints and related products. The method is based on diluting a representative sample, separating the pigment by centrifugation (for liquid paints), and extracting the pigment or powder with dilute hydrochloric acid (HCl, 0.07 mol·L⁻¹). The standard is intended for liquids and powders and does not apply to dry films (see ISO 6714).
Key topics and technical requirements
- Sample preparation and sampling: Follow ISO 1512 and ISO 1513 guidance for representative sampling and sample conditioning before testing.
- Pigment separation: For liquid paints, pigments are separated from the binder by centrifugation. Three separation methods are described depending on binder type (solvent‑based, aqueous polymer emulsions, and non‑aqueous polymer dispersions).
- Solvent selection: Choose a solvent that produces optimal pigment separation; common examples in the standard include toluene/ethanol, xylene/butanol, acetone, tetrahydrofuran and others.
- Acid extraction ratios:
- General soluble‑metal extraction: pigment mass : HCl volume = 1 : 15
- Special case for “soluble” lead when total lead in paint ≥ 1% (m/m): pigment mass : HCl volume = 1 : 1000
- Post‑extraction processing: Evaporate the liquid portion to dryness, perform dry ashing (calcination), and extract the ash with nitric acid for subsequent metal analysis.
- Equipment and controls: Laboratory centrifuge, oven (e.g., 105 ± 2 °C), desiccator, pH meter and filtration apparatus as needed.
- Quality and safety: Procedures are analytically complex and intended for experienced laboratory personnel; blank controls and duplicate extractions are required.
Applications and users
ISO 6713 is used by:
- Independent testing laboratories performing paint composition and metal content analysis
- Manufacturers for quality control of liquid and powder coatings
- Regulatory and environmental agencies assessing soluble heavy metals (notably lead) in paints
- Health & safety teams verifying compliance with limits on soluble metals in consumer and industrial coatings
Practical benefits include standardized extract preparation for consistent downstream metal determinations (e.g., atomic absorption, ICP), clearer comparability of results across labs, and defined procedures for high‑lead formulations.
Related standards
Keywords: ISO 6713, paints and varnishes, acid extracts, preparation of acid extracts, soluble metals, lead testing, centrifugation, hydrochloric acid extraction, powder coatings, paint testing methods.