Overview
ISO 9184-4:1990 - "Paper, board and pulps - Fibre furnish analysis - Part 4: Graff 'C' staining test" specifies the preparation, use and colour reactions of the Graff “C” stain for microscopic fibre identification. This Part is intended to be used together with ISO 9184-1 (general method) and, when needed, other ISO 9184 staining tests (see ISO 9184-2). The Graff “C” method is widely used in pulp and paper laboratories to distinguish most common papermaking fibres by their characteristic colours after staining.
Key topics and technical requirements
- Scope & purpose: Define reagent composition, preparation, application and interpretation of Graff “C” stain for fibre furnish analysis.
- Reagents: Analytical-grade solutions of aluminium chloride, calcium chloride, zinc chloride and iodine are used to prepare the Graff “C” reagent. The standard gives a mixing recipe and storage recommendations.
- Reagent recipe & handling: The published mix proportions (example volumes in the standard) are combined to produce the Graff “C” reagent; solutions and the mixed reagent must be stored in brown dropper bottles, kept in the dark, and periodically refreshed. The iodine solution and reagent should be checked on known reference pulps before use.
- Safety: Several components are toxic; laboratory safety practices and appropriate PPE are required.
- Procedure: Apply 2–3 drops of Graff “C” reagent to a prepared microscope slide, examine at about 40× to 120× magnification, and identify fibres per ISO 9184-1.
- Colour interpretation: The standard provides a colour chart showing expected reactions for major pulp types (e.g., chemical softwoods-yellow/brown; chemical hardwoods-blue/grey; mechanical pulps-vivid yellow; semi-chemical-greenish; cotton/chiffon-bordeaux/red). It cautions that colours vary with operator and pre-treatment, so morphological knowledge and experience are required.
- Quality control: Test new reagent batches on known sulfate and bisulfite softwood samples; adjust iodine if colours are off or prepare a fresh reagent.
Applications and users
- Routine fibre-furnish analysis in pulp & paper mill QA/QC
- Laboratory identification for incoming raw materials and recycled fibre streams
- Research labs characterising blends of chemical, semi-chemical and mechanical pulps
- Forensic and conservation labs assessing paper composition
Typical users: pulp and paper analysts, quality managers, laboratory technicians, and researchers who require reliable microscopic differentiation of kraft vs sulfite, softwood vs hardwood, and other fibre types.
Related standards
- ISO 9184-1: General method for fibre furnish analysis (required companion document)
- ISO 9184-2: Guide to staining (use when additional staining tests are required)
- ISO 9184 (series): Additional parts cover other staining techniques (Herzberg, Loffon‑Merrifield, etc.)
Keywords: ISO 9184-4, Graff C staining, fibre furnish analysis, paper pulp testing, fibre identification, papermaking fibres, staining test, ISO 9184.
