Overview
EN ISO 8780-4:1995 - "Pigments and extenders - Methods of dispersion for assessment of dispersion characteristics - Part 4: Dispersion using a bead mill" specifies a laboratory test method for dispersing pigments and extenders using a bead (ball) mill. The method is intended to be used with agreed binder systems of low to medium viscosity and is focused on assessing dispersion behaviour under reproducible conditions. Annex A lists the supplementary information required to make the method applicable to a particular product or test program.
Key topics and technical requirements
- Scope limitation: Applicable to low- and medium-viscosity mill bases where grinding spheres can move freely; not suitable for very high-viscosity systems.
- Bead mill apparatus: Requirements for the drive unit (shaft speed 1 000–5 000 r/min), stirrer assembly geometry, vessel clearances and recommended peripheral disc speed (adjustable to about 5–7 m/s). Vessel sizes and clearances are specified.
- Grinding spheres: Use identical sphere type and size within test series. Typical examples given: glass beads 1–2 mm (density ≈ 2.6 g/cm3) or steel balls 2–3 mm (density ≈ 7.8 g/cm3, Mohs hardness 7–8). Apparent bead volume ≈ 40% of vessel.
- Binder system and mill base: Binder, solvent, concentration and rheological data (e.g., viscosity or flow time) must be agreed and reported. Preliminary trials determine pigment concentration so spheres move freely; example pigment concentration ranges are provided as starting points.
- Test procedure: Pre-mixing without beads, addition of beads, dispersion at agreed speed and temperature, removal of test aliquots at defined stirring times, de‑aeration and stabilization procedures where necessary.
- Reporting: Test report must identify the product, reference the standard, include the supplementary information from Annex A, note any deviations, and record test dates.
Applications and who uses it
- Practical for quality control, R&D and comparative testing in the coatings, inks, plastics and adhesives industries where pigment/extender dispersion affects colour strength, gloss and grind.
- Used by pigment manufacturers, paint formulators, coatings laboratories and standards organizations to:
- Compare dispersibility of pigments and extenders
- Optimize mill-base formulations and processing parameters
- Provide reproducible data for supplier specifications and QC
Related standards
- EN/ISO 8780 series (Parts 1–6) - introduction and alternative dispersion methods (oscillatory shaking, high-speed impeller mill, automatic mill, triple-roll mill)
- ISO 8781 series - methods of assessment (tinting strength, fineness of grind, gloss)
- ISO 842 (sampling) and ISO 2431 (flow time by flow cups) are normative references used with this method.
Keywords: EN ISO 8780-4:1995, bead mill, pigment dispersion, dispersion characteristics, mill base, grinding spheres, binder system, pigment testing, coatings quality control.
