ISO 638-1:2022

Overview

ISO 638-1:2022 specifies an oven-drying method for the determination of the dry matter content (and complementary moisture content) of paper, board, pulps and cellulosic nanomaterials in solid form. The standard defines the principle, apparatus, sampling and test-piece preparation, drying procedure at 105 °C ± 2 °C, calculation to constant mass, and reporting requirements. It applies to materials made from virgin and/or recycled feedstocks and is commonly used when dry-basis results are needed for chemical or physical laboratory tests.

Key topics and technical requirements

• Scope and applicability: Solid-form paper, board, pulp and cellulosic nanomaterials that do not contain appreciable volatile components other than water at 105 °C ± 2 °C. Not applicable to slush pulp or to determination of saleable mass of pulp lots.
• Principle: Weigh test piece before and after oven-drying until constant mass is reached; calculate dry matter content as the ratio of dry mass to initial mass.
• Temperature and drying: Oven maintained at 105 °C ± 2 °C. Initial drying times vary by sample type and grammage (e.g., ≥30 min for low-grammage sheet material, ≥60 min for >200 g/m2, 4 h for recycling samples), with subsequent re-drying until mass changes ≤0.1% between successive weighings.
• Apparatus: Analytical balance (readability to 1 mg for small pieces), water‑vapour‑proof containers with lids, ventilated oven, desiccator.
• Sampling and preparation: Follow ISO 186, ISO 7213 or EN 17085 as appropriate; protect hygroscopic samples (handle with gloves/tweezers, store in sealed containers) and prepare duplicate test pieces.
• Dissolved solids: This method determines total dry matter including dissolved solids. If only cellulosic solids are desired, remove dissolved solids (washing/dialysis) before testing.
• Safety note: The procedure may involve nanomaterials - follow nanotechnology laboratory safety guidelines.

Practical applications

• Correcting chemical analysis results to a dry basis (e.g., trace metal content reported per oven-dry mass).
• Quality control in paper, board and pulp production, converting and recycling operations where moisture affects processing (printing, dimensional stability, curl).
• Laboratory routine when simultaneous physical or chemical tests require dry-basis normalization.
• Research and characterization of cellulosic nanomaterials (e.g., nanopaper, films, freeze‑dried powders).

Who should use ISO 638-1:2022

• Laboratory technicians and QC analysts in pulp, paper and recycling plants
• Materials scientists and researchers working with cellulosic nanomaterials
• Standards and compliance managers preparing test reports
• Contract laboratories performing moisture/dry-matter determinations

Related standards

• ISO 638-2 (suspensions of cellulosic nanomaterials)
• ISO 287 (moisture content of lots of paper and board)
• ISO 4119 (stock concentration of pulps)
• ISO 186, ISO 7213, EN 17085 (sampling procedures)
• ISO 801 series (saleable mass of pulp lots)

Keywords: ISO 638-1:2022, dry matter content, oven-drying method, paper board pulp, cellulosic nanomaterials, moisture content, laboratory standard.