Overview
ISO 23169:2020 - Paints and varnishes - On-site test methods on quality assessment for interior wall coatings - specifies two standardized, portable test methods to assess the performance of interior wall coatings in situ: on-site cleanability (stain removal) and on-site wet-scrub resistance. The methods are intended for white and light-coloured coatings (tristimulus Y10 > 25 measured on a coating applied to a black substrate) and are designed to evaluate the quality of the entire wall coating system (filler, primer and top coats) under real application conditions.
Key topics and technical requirements
- Two on-site methods:
- Cleanability (stain removal) - applies standardized soiling agents, allows measurement of stain uptake and removal, and quantifies cleanability using tristimulus Y10 measurements before and after cleaning.
- On-site wet-scrub resistance - measures film resistance to wet scrubbing cycles to detect film thickness loss and surface damage.
- Scope limits: Applicable to white/light-coloured coatings with Y10 > 25 on black substrate.
- Performance differentiation:
- Cleanability distinguishes coating quality between 18% pigment volume concentration (PVC) and the critical pigment volume concentration (CPVC).
- Wet-scrub resistance differentiates performance when PVC ≈ CPVC or above.
- Test apparatus & consumables:
- Wet-scrub tester (manual, ~20 ±1 scrub cycles/min, stroke length 180 ±10 mm) with a specified sponge (100 × 35 mm, 15 ±1 mm thick, hardness 55 ±5 kPa) and optional black cloth for wet-scrub tests.
- Spectrophotometer for tristimulus Y10 measurement (per ISO 6504-3).
- Standard soiling agents (water-soluble Nigrosin, alcohol-soluble black solution) and optional agents (vinegar, black tea, blue-black ink).
- Cleaning medium: sodium n‑dodecylbenzenesulfonate solution (2.5 g/l).
- Procedure highlights: apply standardized stains, dry (10 min), perform controlled scrubbing, measure Y10 before/after, calculate cleanability and resistance classes.
Practical applications and users
ISO 23169:2020 is practical for:
- Paint manufacturers (product development and QC)
- On-site quality inspectors and contractors (acceptance testing)
- Specifiers and architects (performance verification)
- Independent test laboratories and building owners (comparative evaluation)
Benefits include objective, repeatable on-site assessment of stain removal and scrubbability, improved specification clarity, and better differentiation of coating systems under real use conditions.
Related standards
- ISO 6504-3 - hiding power and Y10 measurement
- ISO 3696 - water quality for analytical use
- ISO 4618 - paints and varnishes terminology
- ISO 13076 - lighting and visual assessment procedures
- ISO 11998 - laboratory wet-scrub terminology and background
Using ISO 23169:2020 helps stakeholders move from subjective visual checks to standardized, measurable on-site evaluation of interior wall coatings.