Overview
EN ISO 6504-1:2019 - Paints and varnishes: Determination of hiding power - Part 1: Kubelka‑Munk method for white and light‑coloured paints specifies a laboratory method to determine the hiding power (the spreading rate required to achieve 98% hiding) of white and light‑coloured paints. The standard applies to paint films with a tristimulus value Y ≥ 70 and hiding power > 80%, and it is not applicable to fluorescent or metallic paints. The method uses the Kubelka‑Munk optical model and instrument measurements (reflectance) to calculate scattering and absorption properties and derive the spreading rate for 98% opacity.
Key Topics
- Scope and limits: Applicable only to white/light‑coloured coatings meeting Y and hiding power thresholds; excludes fluorescent and metallic formulations.
- Principle: Uses the Kubelka‑Munk equations to relate optical reflectance to scattering and absorption coefficients of pigmented films.
- Measurements required: Reflectance on black and white substrates, controlled film thickness, and density/non‑volatile content per referenced methods. Instruments include a reflectometer, film applicators and specific substrates.
- Test procedure elements: Sampling and preparation, film application, reflectance measurement, film thickness determination, and calculation of wet film thickness and hiding power.
- Supporting material: Annexes provide graphs, tables and calculation examples for converting reflectance data into hiding power (98% criterion).
- Precision and reporting: The standard contains precision statements (repeatability and reproducibility) and defines required test‑report content.
Applications
EN ISO 6504-1:2019 is used across the paint and coatings value chain for:
- Quality control (QC) - routine batch testing to verify hiding performance against product specifications.
- Product development - formulation optimization to balance pigment loading, scattering power and cost while meeting opacity targets.
- Specification and procurement - providing objective hiding power metrics in technical datasheets and contracts.
- Comparative testing - benchmarking white and light colours between suppliers or across formulations.
Typical users include paint and varnish manufacturers, independent test laboratories, R&D chemists, coastal and industrial specifiers, and regulatory/compliance teams.
Related standards
Relevant referenced documents and related parts of the ISO 6504 series:
- ISO 1513 - Examination and preparation of test samples
- ISO 2808 - Determination of film thickness
- ISO 2811‑1 - Density (pycnometer)
- ISO 3251 - Non‑volatile matter content
- ISO 4618 - Terms and definitions (paints and varnishes)
- ISO 15528 - Sampling
- ISO 6504‑3 - Hiding power at fixed spreading rate (related method)
EN ISO 6504‑1:2019 provides a standardized, reproducible approach to quantify hiding power of white and light‑coloured paints using the Kubelka‑Munk model-essential for consistent QC, R&D and specification in coatings industries.
