EN ISO 787-22:2017 specifies a practical comparative test method to evaluate the resistance to bleeding of pigments used in paints and coatings. The method compares a test pigment against an agreed reference sample by applying pigment dispersions to test panels, overcoating with a white composition, and assessing any discoloration (bleeding) visually or instrumentally. This part of the ISO 787 series is intended as a general, broadly applicable procedure for pigments and extenders.
Key topics and technical requirements
- Purpose: Compare bleeding of a pigment under agreed conditions with a reference (agreed) sample. The standard emphasizes a practical, visual comparison rather than purely solvent-solubility tests.
- Sampling: Representative sampling as per ISO 842.
- Test materials:
- Metal or equivalent test panels (e.g., bright tinplate or aluminium), typically 150 mm x 100 mm.
- Agreed medium for pigment dispersion and an agreed white overcoating composition.
- Optional abrasion using silicon carbide paper grade 600 and black-and-white charts for evaluation.
- Application details:
- Prepare dispersions of the test pigment and the agreed sample in the same medium.
- Apply dispersion to two-thirds of panel length to a wet film thickness of 75–120 µm; leave one end uncoated.
- Apply the white overcoating so panels have areas coated only with overcoat, only with pigment dispersion + overcoat, and over a black-and-white chart.
- Dry at ambient or subject to agreed stoving conditions.
- Assessment and reporting:
- Compare in diffuse daylight (or artificial daylight) following ISO 3668; repeat after 24 hours.
- Results expressed as bleeding less than, equal to, or greater than the agreed sample.
- Test report must include pigment ID, reference to ISO 787-22, agreed test conditions, daylight type, result, deviations and date.
Practical applications and users
- Who uses this standard:
- Pigment manufacturers and suppliers (quality control and product comparison)
- Paint, varnish and coatings formulators (compatibility and formulation stability)
- Coatings test laboratories and certification bodies
- R&D teams assessing pigment migration and staining risks
- Typical applications:
- Routine QC checks to confirm new batches match reference bleeding performance
- Comparative assessments during pigment selection for sensitive topcoats
- Supplier-to-customer acceptance tests where an “agreed sample” is used
Related standards
- ISO 787 series - general methods for pigments and extenders (other parts cover colour, density, lightfastness, etc.)
- ISO 842 - Sampling of raw materials for paints and varnishes
- ISO 3668 - Visual comparison of paint colour (used for assessment)
Keywords: EN ISO 787-22:2017, ISO 787-22, resistance to bleeding, pigments, extenders, pigment bleeding test, paint testing, coatings quality control.
