Overview
EN ISO 787-15:2019 - General methods of test for pigments and extenders - Part 15: Comparison of resistance to light of coloured pigments of similar types (ISO 787-15:2019) defines a reproducible, comparative test method for assessing resistance to light / light fastness of coloured pigments. The standard describes how to prepare side‑by‑side specimens of an agreed reference pigment and a test sample, expose them to the same light conditions, and evaluate relative change in appearance.
Key points:
- Two exposure methods: Method A (natural daylight exposure under glass) and Method B (direct artificial light).
- Assessment is made by visual comparison of colour change between test sample and agreed reference pigment.
Key topics and requirements
- Principle: Disperse test and reference pigments in the same binder (medium), apply to an agreed substrate, dry, expose side‑by‑side, and compare colour change.
- Exposure methods:
- Method A: Exposure under a single‑pane glass cover to natural daylight in a ventilated cabinet (protects from rain; specific glass transmittance characteristics are given).
- Method B: Exposure to controlled artificial light (details of light source and apparatus are specified/ agreed).
- Apparatus & materials:
- Substrates (e.g., aluminium or rigid cardboard with white high‑gloss coating, or paper for mass‑tone prints).
- Film applicator to lay down two wet films side‑by‑side (50–100 µm wet thickness) or apparatus for mass‑tone prints (~1.5 µm).
- Opaque cover sheet, grey scale for assessing change (ISO 105‑A02), and agreed reference pigment.
- Test procedure elements:
- Sampling (clause 6), specimen preparation, exposure (clause 7) and reporting (clause 8).
- Parties should agree supplementary details: reference pigment identity, binder composition, dispersion method, exposure angle, and artificial light source parameters.
- Evaluation guidance: Comparisons are recommended when the reference pigment’s change corresponds approximately to grey scale grades 4 and 3 (ISO 105‑A02).
Applications and users
Who uses EN ISO 787-15:2019:
- Pigment manufacturers and suppliers
- Paint, coating and ink formulators
- Quality control and test laboratories
- R&D and product development teams for colour durability
- Procurement/specification engineers assessing comparative light fastness
Practical uses:
- Comparative quality control of pigment batches
- Selecting pigments for outdoor and indoor applications based on relative light fastness
- Supporting product claims and specification development
- Complementing accelerated weathering and application‑specific tests
Related standards
- ISO 105‑A02 - Grey scale for assessing change in colour
- ISO 15528 - Sampling for paints, varnishes and raw materials
- ISO 18451‑1 - Terminology for pigments, dyestuffs and extenders
- CIE Publication No. 20 - Simulated solar radiation recommendations
Keywords: EN ISO 787-15:2019, resistance to light, light fastness, coloured pigments, agreed reference pigment, natural light exposure, artificial light exposure, pigment testing, grey scale.
