ISO 787-18:1983

Overview

ISO 787-18:1983 specifies a standardized test method for determining the residue on a sieve from a sample of pigment or extender using a mechanical flushing procedure. Developed by the International Organization for Standardization (ISO) within Technical Committee ISO/TC 35 (Paints and varnishes), this part of the ISO 787 series ensures consistent and reliable measurement of coarse particles that remain after dispersing materials in water and subjecting them to mechanical flushing.

This standard is applicable to pigments, extenders, and other powders or granules that are insoluble in water, but not suitable for hydrophobic or pelletized materials. It replaces the earlier ISO 787/18-1973, providing improved procedures and updated guidance.

Key Topics

• Scope of Application:

  • Applies to pigments, extenders, and other insoluble powders or granules.
  • Not applicable to hydrophobic or pelletized materials.
  • Specifies that results may differ from manual methods.

• Principle of the Test:

  • The sample is dispersed in water and flushed through a sieve by rotating water jets, separating residue based on particle size.
  • Coarse particles retained on the sieve are dried and precisely weighed to determine the residue.

• Apparatus Required:

  • Mechanical flushing apparatus with rotating water jets.
  • Sieve with a specified nominal mesh aperture (selected according to ISO 565).
  • Oven, desiccator, analytical balance.
  • Wetting agents for samples difficult to disperse.

• Sampling and Reporting:

  • Emphasizes representative sampling following ISO 842.
  • Clear reporting requirements, including sieve aperture, sample size, wetting agents, and any deviations from the procedure.

• Precision and Result Interpretation:

  • Duplicate determinations are required for reliability.
  • If results vary significantly, additional testing and investigation for inhomogeneity are advised.

Applications

ISO 787-18:1983 serves key roles across industries where pigment and extender quality directly affect product performance:

• Paints and Coatings:

  • Assures quality in pigment manufacturing by identifying and quantifying coarse residues.
  • Applies in quality control labs for raw material assessment and product development.

• Industrial Powders:

  • Useful in sectors using granulated or powdered materials, ensuring they meet dissolution, dispersion, and texture specifications.

• Standard Compliance:

  • Enables manufacturers to refer to a harmonized test method in technical specifications.
  • Facilitates international trade by supporting declarations of compliance to widely recognized ISO standards.

• Laboratory Reference:

  • Provides a benchmark for internal quality checks and for comparing materials from different suppliers.

Related Standards

The ISO 787 series covers general test methods for pigments and extenders, facilitating cross-referenced compliance. Key related standards include:

• ISO 787-7: Determination of residue on sieve - Water method - Manual procedure

  • Offers an alternative manual method; results may vary from the mechanical procedure.

• ISO 565: Test sieves - Woven metal wire cloth, perforated plate, and electroformed sheet - Nominal sizes of openings

  • Details sieve specifications required for consistent testing.

• ISO 842: Raw materials for paints and varnishes - Sampling

  • Standardizes sampling methods to ensure representative test results.

• Other ISO 787 Parts:

  • Cover additional properties such as color comparison, matter volatile content, oil absorption, and pH value.

By referencing ISO 787-18:1983, manufacturers, laboratories, and regulatory bodies ensure their testing for pigment and extender residue is accurate, reproducible, and internationally recognized. This enhances product consistency, safety, and competitiveness in the global market.