Overview - ISO 23714:2014 (Water Retention Value for Pulps)
ISO 23714:2014 specifies a standardized laboratory procedure to determine the water retention value (WRV) of all kinds of pulp. WRV is an empirical measure of a pulp test pad’s capacity to hold water after controlled dewatering and centrifugation. The standard defines the principle, required reagents and apparatus, sampling and sample preparation, test procedure, calculation and reporting rules for consistent pulp testing across the paper and pulp supply chain.
Key topics and technical requirements
- Scope: Applies to chemical and mechanical pulps; useful for rewetted and never-dried pulps (report status).
- Principle: Form a test pad on a glass-fibre filter, centrifuge under defined conditions, weigh wet and oven-dry masses, calculate WRV.
- Critical apparatus and reagents:
- Standard water (ISO 14487) or declared alternative
- Büchner funnel with glass-fibre filter (e.g., Whatman GF/C)
- Swing-out centrifuge with buckets; test pad position ≈15 mm from bottom of bucket
- Test-pad-holding units (design examples in Annex A)
- Oven at (105 ± 2) °C; weighing bottles (25 ml)
- Specified test conditions:
- Centrifugal force: (3 000 ± 50) g at the pad for 30 min ± 30 s
- Working temperature: recommended (23 ± 3) °C (report if different)
- Stock pulp concentration: 2–5 g/l (higher for slow-draining pulps)
- Target test-pad oven-dry grammage: (1 700 ± 100) g/m²
- Calculation and quality control:
- WRV = (m_wet / m_dry) − 1 (grams per gram)
- Tests in duplicate; report mean to two decimal places
- Parallel determinations must not differ by more than 5% of their mean
- Reporting: Reference ISO 23714, sample identification, test conditions, sample status (rewetted/never-dried), results and any deviations.
Applications and who uses it
- Pulp producers use WRV to monitor effects of pulping and refining (fibrillation, swelling) on fibre water-holding capacity.
- Papermakers and process engineers use WRV as an indicator of papermaking potential (drainage, retention, bonding).
- Quality control laboratories apply the method for batch acceptance, process control and R&D when optimizing refining or chemical treatments.
- Researchers studying fibre modifications, beating/refining effects, and absorbency characteristics.
Related standards
- ISO 5263-1 / -2 / -3: Laboratory wet disintegration of pulps (sample preparation)
- ISO 7213: Sampling for testing pulps
- ISO 14487: Standard water for physical testing
- ISO/TR 24498: Precision guidance referenced in this edition
Using ISO 23714 ensures reproducible WRV measurement, enabling comparable pulp quality data for process control, product development and specification compliance.