Overview
EN ISO 9117-6:2012, titled Paints and varnishes - Drying tests - Part 6: Print-free test, is an international standard developed by ISO and endorsed by CEN. This standard specifies a straightforward empirical method to evaluate the resistance of paint, varnish, or related coatings to imprinting by a nylon gauze under a controlled force and time. It plays a crucial role in quality assurance by determining the point at which a coating is sufficiently dry to resist marking, known as the print-free state.
The test can be conducted either as a pass/fail evaluation after a specified drying or stoving period or as a time-dependent test to find the exact print-free time by repeated assessments.
Key Topics
- Purpose: This standard measures the resistance of coatings to imprinting marks, indicating the drying stage at which coatings are no longer susceptible to surface damage by light pressure.
- Test Materials: Utilizes woven monofilament polyamide (nylon) gauze squares of defined dimensions and thread diameter, supported by rubber discs and calibrated weights to apply a specific force.
- Test Conditions: The standard specifies environmental conditions for drying (23 ± 2 °C, 50 ± 5% relative humidity), panel preparation, and coating application to ensure consistent and reproducible results.
- Testing Procedure:
- Apply nylon gauze on the coated surface,
- Place a rubber disc and a cylindrical weight on the gauze,
- Maintain pressure for 10 minutes,
- Inspect the coating for any visible imprint using normal corrected vision.
- Assessment Outcomes:
- Print-free state means no imprint is visible, indicating adequate drying,
- The exact print-free time can be established by testing at intervals until the coating consistently resists impressions.
- Reporting Requirements: Detailed documentation covering product information, panel preparation, coating thickness, test conditions, gauze specifications, results, and any procedural deviations.
Applications
- Quality Control in Paint Manufacturing: Ensures coatings meet drying performance standards to avoid surface defects during handling and application.
- Evaluation of Protective Coatings: Applicable in automotive, aerospace, and industrial sectors to verify surface durability before further processing.
- Research and Development: Helps formulate coatings with optimized drying times and resistance to marking.
- Compliance Testing: Meets regulatory and contractual requirements by providing standardized validation of drying and curing processes.
This print-free test is particularly beneficial in industries where the aesthetic and functional integrity of coatings is critical, guaranteeing end-user satisfaction and product performance.
Related Standards
EN ISO 9117 part 6 is part of a broader series of paint drying tests, which include:
Additional referenced standards supporting this method:
- ISO 1513: Sample examination and preparation,
- ISO 1514: Standard panels for testing,
- ISO 2808: Film thickness determination,
- ISO 15528: Sampling of paints and varnishes,
- ISO 3270: Climatic conditions for conditioning and testing coatings.
Adopting EN ISO 9117-6:2012 streamlines the evaluation of coating dryness and resistance to marking, promoting consistent product quality across the paints and varnishes industry worldwide.
