ISO 8780-4:1990

Overview

ISO 8780-4:1990 defines a standardized method for assessing dispersion characteristics of pigments and extenders by using a bead mill. The method is intended for low- and medium-viscosity mill bases that allow free movement of grinding spheres and is to be used in conjunction with ISO 8780-1 (Introduction) and the assessment procedures in ISO 8781 series. Practical repeatability is achieved by agreeing and recording key test parameters and supplying the supplementary information listed in Annex A.

Key Topics

• Scope and applicability: Restricted to mill bases where grinding spheres can move freely; suitable when higher viscosity mill bases are required than those for other dispersion methods.
• Apparatus essentials: A bead mill with a drive unit capable of 1000–5000 r/min, adjustable impeller-disc peripheral speed, and a vessel with minimum clearances (e.g., 10 mm between discs and vessel wall/base).
• Grinding spheres: Use spheres of the same type, size and density across a test series; conditioned if unused. The apparent sphere volume should be approximately 40% of vessel volume.
• Binder system and mill base: The binder, solvent and concentration (and rheological data such as viscosity or flow time) must be agreed and recorded. The same binder batch should be used across series.
• Procedure highlights: Pre-mix pigment with binder until wet, add grinding spheres, disperse at the agreed peripheral speed, take test portions at agreed stirring times (examples: 4, 8, 16, 32 min), stabilize and de-aerate test portions as required.
• Reporting: Test report must identify product, reference this part of ISO 8780, list supplementary information from Annex A, record deviations, and give test dates.

Applications

• Quality control of pigment and extender dispersibility in coatings, inks and related formulations.
• Comparative testing during development to optimize mill-base composition, sphere type, and processing times.
• Establishing reproducible production procedures and acceptance criteria for low- to medium-viscosity systems.

Practical benefits include repeatable evaluation of dispersibility, clear documentation of test parameters (mill geometry, sphere diameter and density, binder composition, stirring times), and the ability to correlate dispersion performance with downstream properties such as tinting strength, fineness of grind or gloss (as assessed in related ISO 8781 parts).

Related Standards

• ISO 8780-1:1990 - Introduction to dispersion methods and assessment principles
• ISO 8780-2 / -3 / -5 / -6 - Other dispersion methods (oscillatory shaker, high-speed impeller mill, automatic miller, triple-roll mill)
• ISO 8781 series - Assessment procedures (tinting strength, fineness of grind, gloss)
• ISO 842:1984 - Sampling of raw materials for paints and varnishes
• ISO 2431:1984 - Flow cups (used to characterise binder rheology)

Follow ISO 8780-4:1990 to ensure consistent, documented bead-mill dispersion testing and to support robust quality and development workflows for pigment and extender handling in mill bases.