Overview
ISO 5350-3:2007 specifies a standardized procedure for the visual estimation of visible dirt and shives in pulps using reflected light and the Equivalent Black Area (EBA) method. The method is applicable to all types of dry or wet pulp - sheeted or rolled, including recycled pulp - and reports contamination as the number of contraries per square metre and their total EBA (mm²/m²). The standard complements ISO 5350-1 and ISO 5350-2 (transmitted‑light methods) and ISO 5350-4 (instrumental reflected‑light method).
Key Topics
- Principle: Visual inspection of both sides of pulp test pieces under reflected light; each speck’s visual impact is estimated by comparison with standard black spots on the EBA comparison chart.
- EBA definition: The visual area of a reference black spot on the white chart that appears equivalent in noticeability to the dirt speck on the pulp.
- Apparatus & lighting: Use a reflected‑light viewer or lighting providing about 1 700 cd/m² on the specimen. Do not use magnifiers for size estimation.
- Comparison chart: A photographic chart of round black spots on a white background (white reflectance ≈ 81.5%, black ≈ 2.4%). Only original photographic charts (not photocopies or prints) give valid results.
- Sampling & preparation: Follow ISO 7213 sampling. Select 10 or more sheets (preferably 20) with at least 0.15 m² exposed area per side; for never‑dried pulp form laboratory sheets per ISO 5269.
- Procedure: Inspect at right angles, brush away loose debris, estimate each speck’s EBA from the chart. For low‑dirt pulps check all specks ≥ 0.04 mm²; for high‑dirt pulps use a reference spot and masking technique to speed counting.
- Results & uncertainty: Report number of contraries per m² and EBA (mm²/m²). Counting uncertainty follows a Poisson‑like distribution and improves with higher counts.
Applications
- Quality control in pulp mills and paper mills for incoming/outgoing pulp inspection
- Acceptance testing for recycled pulp blends
- Purchasing specifications and supplier verification
- R&D and process troubleshooting to reduce visible particulate contamination
- Laboratory testing in third‑party testing services and certification
Who uses it: pulp mill QA/QC teams, paper manufacturers, laboratory technicians, procurement specialists, and recycling operations.
Related Standards
- ISO 5350-1: Inspection by transmitted light (laboratory sheets)
- ISO 5350-2: Inspection by transmitted light (mill sheets)
- ISO 5350-4: Instrumental reflected‑light EBA method
- ISO 5269-1 / ISO 5269-2: Preparation of laboratory sheets
- ISO 7213: Sampling for testing
- TAPPI T 213 (equivalent comparison chart used)
Keywords: ISO 5350-3, EBA method, Equivalent Black Area, pulp inspection, dirt and shives estimation, reflected light, pulp quality control, paper industry.
Open preview (PDF)Pulps - Estimation of dirt and shives — Part 3: Visual inspection by reflected light using Equivalent Black Area (EBA) method