Overview
EN ISO 28199-3:2021 - Paints and varnishes - Evaluation of properties of coating systems related to the spray application process - Part 3: Assessment of sagging, formation of bubbles, pinholing and hiding power (ISO 28199-3:2021) specifies visual and instrumental methods to assess common defects that occur when coatings are applied by spray. The standard defines how to evaluate sagging, bubble formation, pinholing/cratering and hiding power on test panels prepared under defined spray conditions, and describes how measurements and photographic techniques can be used to support visual assessment.
Key topics and requirements
- Scope and purpose: Methods for assessing tendency to sag, bubble formation limit, pinholing/cratering and hiding power for coatings applied by spray.
- Visual assessment methods: Standardized visual inspection criteria for runs/sags, bubbles and pinholes after drying/curing.
- Measuring techniques: Use of objective measurement and imaging (including 3‑D photographs and profiles for bubbles and pinholes) to complement visual grading.
- Definitions: Terms such as bubble formation limit and cratering are defined to ensure consistent interpretation.
- Test preparation and film thickness: Evaluations are performed on test panels prepared in accordance with ISO 28199‑1; film thickness is measured as specified in the series.
- Reporting: Requirements for test reports to record assessment results, conditions and measured values.
Practical applications
- Quality control of spray-applied coatings in production lines (automotive, industrial, plastics).
- R&D and formulation optimization to reduce sagging, pinholing or bubble defects.
- Supplier and customer acceptance testing and troubleshooting of application issues.
- Process validation when changing spray equipment, coatings or application parameters.
- Comparative performance testing across formulations or process conditions.
Who should use this standard
- Coating formulators and R&D laboratories
- QA/QC and production engineers in automotive and industrial coating sectors
- Independent test laboratories and certification bodies
- Specifiers and procurement teams requiring objective acceptance criteria
Related standards
- ISO 28199-1:2021 - Vocabulary and preparation of test panels (used together with Part 3)
- ISO 6504-3 - Determination of hiding power (referenced norm)
- Other parts of the ISO 28199 series covering colour, gloss and surface texture (for complete process evaluation)
This standard is essential for anyone needing standardized, repeatable methods to evaluate spray application defects and hiding performance, enabling improved coating quality, reproducibility and clearer supplier specifications. Keywords: EN ISO 28199-3:2021, paints and varnishes, spray application, sagging, bubbles, pinholing, hiding power, coating systems, visual assessment, measuring techniques.