Overview
ISO 9117-4:2012 - "Paints and varnishes - Drying tests - Part 4: Test using a mechanical recorder" specifies a laboratory test to determine the times required for organic coatings to reach defined drying stages using a mechanical straight‑line or circular drying‑time recorder. The method is designed to compare drying behaviour (gelation, scratch resistance, tackiness) of coatings of the same generic type and to simulate conditions such as when painted articles are stacked.
Keywords: ISO 9117-4:2012, paints and varnishes, drying tests, mechanical recorder, drying time, coatings.
Key topics and technical requirements
- Principle: Two methods are described:
- Method A - straight‑line recorder: multiple 300 mm × 25 mm glass strips with 2 mm rounded stylets pulled at defined constant speed.
- Method B - circular recorder: ~150 mm × 150 mm glass plate with a PTFE stylus describing an arc at constant speed.
- Measured drying stages: touch‑dry, tack‑free (off‑tack), dry and hard, and through‑dry (dry‑to‑core). Observations are made from the stylus trace and compared to reference figures.
- Sample preparation and panels: use clean glass panels per ISO 1514; sample prep and application follow ISO 1513 and manufacturer or agreement‑specified film thickness. Film thickness measured per ISO 2808.
- Test conditions: perform at least duplicate tests at (23 ± 2) °C and ambient relative humidity unless otherwise agreed (see ISO 3270 for conditioning).
- Apparatus specifics: stylet diameters, weights (e.g., 5 g for straight‑line, ~12 g PTFE for circular), selectable speeds to cover different drying durations (1 h, 6 h, 12 h, 24 h).
- Reporting: test report must identify the product, reference ISO 9117-4, detail panel preparation, application method and drying intervals, recorder type and parameters, and measured times.
Applications and who uses it
- Quality control and R&D for coating formulators and manufacturers to compare drying behaviour after formulation changes.
- Contractors and specifiers assessing suitability of coatings where handling, stacking or early use is critical.
- Independent test laboratories verifying compliance, producing comparative data for technical datasheets.
- Uses: optimizing production schedules, packaging/stacking processes, specifying coatings for fast return‑to‑service or scratch resistance.
Related standards
This standard is practical for anyone needing repeatable, comparative drying‑time data for organic coatings, especially when mechanical recorder traces provide insight into gelation, tackiness and resistance during early film formation.
