Overview
EN ISO 8781-2:1995 (ISO 8781-2:1990) defines a laboratory method to assess the dispersion characteristics of pigments and extenders by monitoring the change in fineness of grind during staged dispersion. The standard is intended for comparative testing (for example, a test pigment versus an agreed reference pigment) and requires dispersion in an agreed binder system with fineness-of-grind measurements taken after each incremental milling stage.
Key topics and requirements
- Principle: Plot fineness-of-grind (µm) as a function of dispersion work (time, number of revolutions, etc.) and determine, by interpolation, the work required to reach an agreed fineness target.
- Sampling: Disperse each pigment in at least four stages; intermediate stages should follow a geometric progression. Final stage should reach or exceed the agreed fineness where possible.
- Measurement: Determine fineness of grind using the method in ISO 1524. Use a fineness-of-grind gauge (maximum groove depth 50 µm or 100 µm; 50 µm preferred) and remove small samples with a spatula after each stage.
- Apparatus: Ordinary laboratory glassware plus fineness-of-grind gauge and spatula; dispersion method selected from ISO 8780 series (e.g., high-speed impeller mill, bead mill, triple-roll mill, automatic muller).
- Reporting: Include identification, reference to EN ISO 8781-2 and the relevant ISO 8780 part, supplementary information (Annex A), dispersion work and target fineness (or highest practically attainable fineness), plotted graph, any deviations, and test dates.
- Supplementary information (Annex A): Required items include the dispersion method, binder type/designation, target fineness, and any reference pigment.
Practical applications
- Quality control and acceptance testing of pigments and extenders based on dispersion performance.
- Comparative R&D to rank pigments by ease of dispersion for coatings, inks, plastics and varnishes.
- Optimization of milling processes (milling time, revolutions, choice of mill) by linking dispersion work to fineness achieved.
- Supplier qualification and formulation decision-making where consistent pigment dispersion is critical to color strength, gloss and rheology.
Who should use this standard
- Pigment and extender manufacturers
- Paint, ink and coatings formulators and QC laboratories
- Process engineers and production mills optimizing dispersion operations
- R&D teams evaluating new pigments or dispersing technologies
Related standards
- ISO 1524 - Determination of fineness of grind
- ISO 8780 series (Parts 1–6) - Methods of dispersion (e.g., impeller mill, bead mill, triple-roll mill, automatic muller)
- EN/ISO 8781 parts 1 and 3 - Other assessment approaches within the same family
Keywords: EN ISO 8781-2, ISO 8781-2, pigment dispersion, fineness of grind, dispersion characteristics, fineness-of-grind gauge, ISO 1524, binder system, milling time, pigment testing.
