Overview
ISO 12194:1995 - "Leaf tobacco - Determination of strip particle size" specifies a standardised sieving method to measure particle-size distribution of strips (long pieces of threshed or stripped lamina) of leaf tobacco. The method separates a representative sample into five size fractions by passing it over four stacked screens mounted on a purpose-built quality‑control shaker. The standard is aimed at consistent, repeatable measurement for production quality control and laboratory testing.
Key topics and technical requirements
- Sampling mass
- Flue-cured and burley cigarette lamina: 3 000 ± 300 g
- Cigar lamina: 1 000 ± 100 g
- Moisture of samples is typically ~16–20 %; handle dry lamina carefully to avoid degradation.
- Apparatus
- Quality‑control shaker: feed‑band conveyor, four sieving trays, fines collection bin, breaker bars and discharge bins.
- Screens: four wire‑mesh sieves with nominal openings 25.40 mm, 12.70 mm, 6.35 mm, 2.36 mm (mesh and wire diameters conform to ISO 3310‑1).
- Screens are stacked so material passing one screen is exposed to at least 660 mm of the next.
- Breaker bars on decks to break lamina lumps.
- Operating parameters
- Vibration frequency: 525 ± 5 vibrations per minute (drive shaft speed checked by tachometer).
- Screen stroke: 13.1 ± 1.2 mm (checked using the stroke indicator method in annex B).
- Sample feed adjusted so full sample discharges in 450 ± 5 s.
- Procedure and results
- Spread sample evenly on feedband, run shaker, brush trapped particles from breaker bars and screens, collect fractions in tared bins.
- Weigh fractions to the nearest gram and report each as a percentage of the sum of individual masses. Verify sum is within ±50 g of the initial sample mass; otherwise repeat.
- Documentation
- Test report must include operating details, deviations and full sample identification; annexes A–C provide informative illustrations and component examples.
Applications and users
- Tobacco manufacturers - routine production quality control and monitoring of threshing/stripping processes.
- Lab analysts and QC teams - formal particle‑size distribution testing for process optimisation and lot acceptance.
- Equipment suppliers and maintenance crews - design, calibration and verification of shakers and screens.
- Regulators and researchers - standardised data for product classification, process studies or comparative testing.
Related standards
- ISO 3310‑1 (Test sieves - Technical requirements and testing) - referenced for sieve construction and specifications.
- Prepared by ISO/TC 126 (Tobacco and tobacco products), Subcommittee SC 2 (Leaf tobacco).
Keywords: ISO 12194, leaf tobacco, strip particle size, particle size determination, tobacco quality control, sieving method, quality‑control shaker, sampling procedure.