EN ISO 8780-5:1995 (ISO 8780-5:1990) specifies a laboratory method for assessing pigment and extender dispersion using an automatic muller (plate-type mill). The procedure is designed for comparing small sample lots in pigment quality control and is restricted to high‑viscosity mill bases. Tests are carried out using an agreed binder system (preferably high viscosity and free from volatile solvents) and supplemented by details given in Annex A.
Key topics and technical requirements
- Scope: Comparative quality-control testing of pigments/extenders in high-viscosity mill bases; method to be used with ISO 8781 assessment procedures (tinting strength, fineness of grind, gloss).
- Apparatus: Automatic muller with ground-glass plates (diameter 180–250 mm), adjustable plate load up to 1 kN, driven plate speed 70–120 r/min, and preset revolutions in multiples of 25.
- Mill base and binder:
- Binder system must be agreed between parties and reported in the test report (type, solvent, concentration, rheological data such as viscosity).
- Typical pigment concentrations for mill base: low binder demand 65% m/m; medium 40% m/m; high 25% m/m.
- Procedure:
- Prepare representative sample per ISO 842; pre-condition new plates by 1 000 revolutions with a pigment paste.
- Place mill base on the lower plate, pre-mix with spatula, close plates and mill under agreed load, speed and sequence (example grinding stages: 50, 100, 200, 400 revolutions with intermediate sampling).
- Monitor temperature rise (≤ 10 °C recommended where no water cooling).
- Stabilize test portions if needed (adding binder/additives) - stabilization method must be agreed and recorded.
- Reporting: Include product ID, reference to EN ISO 8780-5, all supplementary information from Annex A (muller details, binder, mill base composition and temperature, dispersion conditions, stabilization), deviations and test dates.
Practical applications and users
- Who uses it: pigment and extender manufacturers, coatings and ink formulators, QC laboratories, R&D teams, and standards laboratories performing comparative dispersibility tests.
- Why use it: to generate repeatable, documented dispersion data for quality control, formulation development and supplier comparison when using high‑viscosity mill bases and an agreed binder system.
- Limitations: method is restricted to high‑viscosity mill bases and the standard cautions about the comparability of results across different dispersion methods - use agreed supplementary information (Annex A) to support meaningful comparisons.
Related standards
- ISO 8780 series (Parts 1–6)
- ISO 8781 (methods of assessment such as tinting strength, fineness of grind, gloss)
- ISO 842 (sampling of raw materials for paints and varnishes)
Keywords: EN ISO 8780-5:1995, ISO 8780-5, automatic muller, pigment dispersibility, mill base, binder system, high-viscosity dispersion, pigment quality control.
