Overview
ISO 536:2019 - "Paper and board - Determination of grammage" specifies a standardized test method to determine the mass per unit area (grammage) of paper and board, expressed in grams per square metre (g/m²). The fourth edition (2019) updates procedural clarifications, reporting requirements and guidance on reduced test areas and "as‑taken" measurements.
Key topics and technical requirements
- Scope: Method for determining grammage of paper and board.
- Principle: Determine the area and mass of test pieces and calculate grammage (mass per unit area). ISO 536 provides the calculation details and required expression of results.
- Apparatus:
- Cutting device capable of producing test pieces within ±1.0% of the nominal area (if not achievable, measure each piece).
- Balance accurate to ±0.5% of mass range and sensitive to detect ±0.2% changes. Use of special sheet‑weighing balances is permitted when calibrated.
- Test piece area: Preferred area 50 000 mm² to 100 000 mm² (e.g., 200 × 250 mm). Where sample is limited, a minimum area of 10 000 mm² may be used but must be reported as a deviation.
- Sampling and replicates: Follow ISO 186 for sampling. ISO 536 recommends at least five specimens and a total area sufficient for at least 20 test pieces, taking the same number from each specimen when possible.
- Conditioning and variants: Condition specimens per ISO 187 for conditioned grammage. Annex A covers oven‑dry determination (use ISO 287 for drying) and "as‑taken" grammage (measure in the condition at sampling).
- Calculation and reporting: Calculate individual grammage values, then report the mean and standard deviation (to three significant figures). The test report must include reference to ISO 536, date/place, sample identification, conditioning atmosphere (unless “as‑taken”), test piece condition, area, number of replicates, results and any deviations from procedure.
- Precision: Annex B provides repeatability and reproducibility data from interlaboratory (CEPI‑CTS) studies and explains limits and uncertainty considerations.
Applications and users
ISO 536 is essential for:
- Paper and board manufacturers for quality control and specification compliance.
- Converters and printers verifying substrate weight for processing, cost and print performance.
- Laboratory technicians conducting routine material testing.
- Procurement and quality assurance teams requiring reproducible grammage measurements for contracts and acceptance testing.
- Researchers assessing material properties where mass per unit area is a critical parameter.
Keywords: ISO 536:2019, grammage determination, paper testing standard, mass per unit area, paper and board grammage, sampling, conditioning, oven‑dry grammage.
Related standards
- ISO 186 - Sampling to determine average quality
- ISO 187 - Standard atmosphere for conditioning and testing
- ISO 287 - Determination of moisture content - Oven‑drying method
- ISO/TR 24498, ISO 5725-1 and TAPPI T 1200 (referenced for precision and interlaboratory evaluation)
