ISO 787-7:2009

Overview

ISO 787-7:2009 defines a manual water method for the determination of residue on sieve from samples of pigments and extenders dispersed in water. The method is part of the ISO 787 series of general test methods for pigments and extenders and is intended to provide a reproducible procedure for assessing coarse material, agglomerates or foreign matter retained by a specified sieve.

This standard is applicable when a clear specification requires the manual water method; note that results can differ from the mechanical flushing procedure described in ISO 787-18, so the chosen method must be stated in the specification and the test report.

Key Topics

• Scope and purpose: Determine mass of residue retained on a sieve after dispersing a test portion in water and rinsing.
• Sampling: Use representative sampling per ISO 15528.
• Apparatus:
  • Test sieve conforming to ISO 565 (nominal mesh aperture and diameter must be reported).
  • Brush (hog bristle) for optional breaking of agglomerates.
  • Sintered-glass crucible (porosity P40) or 50 ml beaker for collecting residue.
  • Oven capable of (105 ± 2) °C, balances with required accuracy, desiccator, washbottle.
• Test portion: Typically 10 g to 100 g; up to 1 000 g where residue is very low.
• Dispersion: Disperse in 300–600 ml water with an agreed dispersing agent (commonly 0.2 %–0.5 % of test portion). If mechanical stirring is required, follow ISO 3262-9 and record stirrer speed and use.
• Procedure essentials:
  • Carry out determinations in duplicate.
  • Pour dispersion through the sieve, rinse until washings are clear.
  • Optionally, break up agglomerates with a brush if agreed.
  • Transfer residue to crucible or beaker, dry at (105 ± 2) °C for 1 h (or lower if residue melts), cool in desiccator and weigh to nearest 1 mg.
  • Repeat the test if duplicate results differ by more than 10 % of the larger value (unless difference < 5 mg).
• Expression of results: Report residue as percentage by mass (mean of two valid determinations); report values below 0.01 % as "less than 0,01 %".

Applications

• Quality control of pigments and extenders for paints, coatings and related materials.
• Verification of compliance with product specifications that limit coarse particles or foreign matter.
• Process monitoring where particle-size distribution and agglomeration affect product performance.

Benefits:

• Provides a standardized, manual test method for consistent reporting.
• Useful where mechanical flushing gives different outcomes or is not appropriate.

Related Standards

• ISO 787-18 - Mechanical flushing procedure for residue on sieve (alternative method).
• ISO 565 - Test sieve specifications.
• ISO 4793 - Sintered-glass filter porosity grading (P40 reference).
• ISO 15528 - Sampling of paints, varnishes and raw materials.
• ISO 3262-9 - Stirrer specifications for extenders (referenced for mechanical dispersion).

For test reporting, include identification of product, reference to ISO 787-7, test result, sieve aperture and diameter, test portion mass, dispersion method and dispersant details, whether agglomerates were broken up, residue description, any deviations, and date of test.