Overview
ISO 12195:1995 specifies a standardized laboratory method for determining the residual stem content of threshed tobacco strips. The procedure uses a small-scale stem tester (a thresher combined with a separating tower) to separate lamina from stem, collect residual stems, and report stem content as a percentage of the original sample mass. The method is applicable to strips produced by mechanical threshing or hand‑stripping from major tobacco types (flue‑cured, burley, cigar, etc.).
Key topics and technical requirements
- Scope & definitions: Clear definitions for stem, lamina, strips, threshing and stripping are provided to ensure consistent interpretation.
- Apparatus specification: The standard gives detailed requirements for the stem tester components, including:
- static pressure tapping apparatus and manometer for air‑flow monitoring,
- stem‑deflector plates, dampers (A–D) and thresher basket,
- specified shaft speeds, vibrating conveyor and tangential separators,
- a fan with minimum airflow capability,
- stacked sieve‑type shaker for further categorization of stem particle sizes.
- Air‑flow calibration: Annex A describes the disc method to set the separating tower to a Standard air‑flow condition (using heavy/light discs) so results are reproducible across altitude and temperature differences.
- Sampling & test cycle: The method describes how to take and feed a representative sample of strips, run a timed cycle through the stem tester (including a second pass for light strips), collect stem product and allow discharge time before weighing.
- Classification & calculation:
- Stem fractions are categorized by sieve sizes (e.g., >2.38 mm,
