Overview
SIST EN ISO 787-1:2018, titled General methods of test for pigments and extenders - Part 1: Comparison of colour of pigments, is a standardized procedure developed by CEN and ISO/TC 35 for assessing the colour consistency of coloured pigments. It specifies a comparison method between a test pigment and an agreed reference sample, ensuring reliable and reproducible colour evaluation. This standard replaces ISO/R 787/1:1968 and is widely recognized in the paint, coatings, and pigment manufacturing industries.
Key Topics
- Scope: Defines a general method for comparing pigment colour using either an automatic or a hand-operated muller, focusing on visual and instrumental evaluation against an agreed standard.
- Binder Use: The binder for pigment dispersion must be mutually agreed upon. If unspecified, refined linseed oil compliant with ISO 150 should be used, facilitating consistent sample preparation.
- Apparatus and Materials: Utilizes tools such as:
- Automatic muller with controlled force and rotational speed (reference method)
- Hand muller or palette knife for manual dispersion
- Standard substrates like glass or marble plates for sample spreading
- Burette for accurate binder dosing
- Sample Preparation: Detailed instructions on mixing pigment with binder to create uniform pastes, emphasizing consistency in paste thickness and texture for valid colour comparison.
- Colour Comparison Procedure: Involves spreading pigment pastes side-by-side on substrates and comparing them under diffuse daylight or controlled light conditions per ISO 3668 guidelines. Optionally, colorimeters may be used by agreement.
- Test Reporting: Mandates documentation of key parameters such as pigment identification, binder type, method used, test results, and any deviations, ensuring traceability and transparency.
Applications
- Quality Control in Pigment Production: Ensures batch-to-batch colour consistency, vital for manufacturer reputation and product performance.
- Paints and Coatings Industries: Helps manufacturers verify pigment colour matches specifications before formulation, preventing costly rework.
- Research and Development: Supports pigment and extender formulation optimization by providing reliable colour comparison methods.
- Contractual Agreements: Provides an objective means for suppliers and customers to agree on pigment colour standards, reducing disputes.
- Regulatory Compliance: Assists companies in meeting quality standards and industry regulations related to pigments and colour quality in coatings and related products.
Related Standards
- ISO 3668: Specifies methods for visual colour comparison of paints and varnishes, supplementing the comparison procedure defined in EN ISO 787-1.
- ISO 150: Defines quality and testing for raw and refined linseed oil used as a binder in pigment testing.
- ISO 842: Addresses sampling methods for raw materials like pigments to ensure representative testing samples.
- Other parts of ISO 787 series, including:
- Part 2: Determination of volatile matter
- Part 5: Determination of oil absorption
- Part 16: Comparison of relative tinting strength using an automatic muller
These provide a comprehensive framework for pigment and extender testing beyond colour comparison.
Keywords: pigment colour comparison, pigment testing standards, automatic muller method, binder for pigments, linseed oil binder, quality control pigments, ISO pigment test methods, paint pigment evaluation, CEN pigment standards.
