ISO 9117-3:2010

Overview

ISO 9117-3:2010 describes a standardized surface-drying test for paints and varnishes that dry by air action or by chemical reaction of components. The method uses small transparent glass spheres (ballotini) to assess whether a coating is surface-dry without damaging the film. It is not intended for stoving products and can be used either as a timed determination of surface-drying time or as a go/no-go compliance check.

Key Topics

• Principle: A coating on a prepared panel is allowed to dry under specified conditions. Ballotini are poured onto the surface and lightly brushed away; a coating is surface‑dry if the spheres can be removed without surface damage.
• Apparatus & materials:
  • Ballotini sieved to pass 250 µm and retained on 125 µm.
  • Soft‑haired brush, stopwatch (0.1 s), balance (0.01 g).
  • Test panels (glass, burnished steel, burnished tinplate or burnished aluminium) prepared per ISO 1514.
• Procedure highlights:
  • Typical sample: ~0.5 g ballotini poured from 50–150 mm; pouring via a glass tube (~25 mm ID) is recommended to localize the test area.
  • After ~10 s, tilt the panel ~20° and brush lightly.
  • Areas within ~5 mm of panel edges are not considered.
  • Either assess at a specified time (go/no-go) or test at intervals on multiple panels or separate areas until the surface-dry moment is obtained.
• Sampling & preparation: Follow ISO 15528 for sampling and ISO 1513 for sample preparation. Measure dry film thickness per ISO 2808.
• Precision: No precision data are provided in the standard.

Applications

• Quality control: Rapid go/no-go checks to verify whether an applied coating meets required surface-dry criteria.
• Product development: Comparative determination of surface-drying behavior for formulation optimization of air‑drying paints and varnishes.
• Specification compliance: Documented surface-dry times and test conditions support contractual and regulatory compliance assessments.

Related Standards

• ISO 9117 (series) - Drying tests for paints and varnishes (Parts 1–5; Part 3 is this ballotini method).
• ISO 1513 - Examination and preparation of test samples.
• ISO 1514 - Standard panels for testing.
• ISO 15528 - Sampling of paints, varnishes and raw materials.
• ISO 2808 - Determination of film thickness.

Practical value

ISO 9117-3:2010 provides a simple, repeatable technique to evaluate surface-drying without specialized instrumentation. The method's limited apparatus requirements and clear reporting clauses (including panel prep, coating thickness, drying times, test results and deviations) make it suitable for laboratory QC, production checks and comparative R&D work where air-drying behavior is critical.