Overview
ISO 5267-2:2025, issued by the International Organization for Standardization (ISO), specifies the methodology for determining the drainability of pulp suspensions using the "Canadian Standard" freeness method. This internationally recognized procedure measures how easily water can be drained from a pulp suspension, reporting the result in millilitres. The test is applicable to all types of pulps in aqueous suspension, forming a critical index for evaluating pulp processability and readiness for papermaking. As the third edition, ISO 5267-2:2025 includes updated references, clarifies prior ambiguities, and ensures alignment with current ISO practices.
Key Topics
- Canadian Standard Freeness Method: This method provides an objective measurement of pulp drainability, widely used across paper and pulp industries to assess fibre surface conditions and the effect of mechanical treatment.
- Applicability: The method is suited for all pulp types in water suspension, though special attention is required when high proportions of fines are present, as these can cause anomalously high readings at low values (false freeness).
- Standardized Test Procedure:
- Preparation of diluted pulp samples using standard water at a controlled temperature, typically 20°C.
- Drainage of a fixed volume of pulp suspension through a standard screen plate in the Canadian Standard freeness tester.
- Measurement of filtrate collected from the side orifice to determine the freeness value.
- Instrument Calibration and Maintenance:
- Calibration and periodic field checks ensure accurate, reproducible results.
- Regular maintenance and cleaning of the tester, particularly the screen plate, are required for consistent operation.
- Traceability to a master reference screen plate is essential for reliable performance.
Applications
ISO 5267-2:2025 is a valuable tool in the pulp and paper industry for:
- Process Control: Monitoring and optimizing refining processes to achieve desired fibre properties for specific paper grades.
- Quality Assurance: Ensuring consistency in pulp characteristics before further processing or delivery to clients.
- Research & Development: Evaluating the impact of new pulping methods, chemical treatments, or raw materials on drainability and fibre quality.
- Standardization in Trade: Providing a common reference for buyer-supplier agreements regarding pulp quality and usability.
- Comparative Studies: Facilitating benchmarking across mills, suppliers, or research facilities by using a recognized international standard.
Related Standards
For comprehensive pulp testing and quality assurance, ISO 5267-2:2025 is used alongside other standards:
- ISO 5267-1: Pulps - Determination of drainability - Part 1: Schopper-Riegler method
- ISO 4119: Pulps - Determination of stock concentration
- ISO 4046 (all parts): Paper, board, pulps and related terms - Vocabulary
- ISO 5269-1: Pulps - Preparation of laboratory sheets for physical testing - Conventional sheet-former method
- ISO 5269-2: Pulps - Preparation of laboratory sheets for physical testing - Rapid-Köthen method
- ISO 14487: Pulps - Standard water for physical testing
Practical Value
Implementing ISO 5267-2:2025 ensures repeatable, accurate freeness measurements, crucial for optimizing papermaking performance, controlling fibre characteristics, and meeting industry or regulatory benchmarks. Its use facilitates efficient communication of test results, supports compliance in international trade, and underpins ongoing process improvements, directly impacting product quality and operational costs.
Keywords: ISO 5267-2:2025, Canadian Standard Freeness, pulp drainability, pulp testing standards, papermaking, pulp quality, laboratory testing, pulp suspension, process control, ISO pulp standards.