Determining Bast Fibre Linear Density by Air Permeability Methods
Air permeability testing measures specific surface area to derive bast fibre linear density, requiring precise moisture conditioning and shive removal.
Cut-and-Weigh Gravimetric Method
Quantitative Analysis
Mass per unit length provides a direct measurement of the linear density of a flax specimen. Utilizing the cut-and-weigh gravimetric method involves the precise division of a fibre bundle into known lengths for weighing on a balance. The resulting value defines the fineness of the material at a fundamental level.
Testing of this type is limited by the manual dexterity required to align and cut the strands without loss.
Laboratory Procedure
Technicians align a bundle of parallel fibres and use a specialized cutter to remove sections of a specific length. The cut-and-weigh gravimetric method requires a high-precision analytical balance to record the mass of the trimmed segments. By dividing the total weight by the sum of the lengths, the operator calculates the average fineness of the lot.
This process remains the primary reference for calibrating indirect fineness testers. Accuracy depends on the sample being free of moisture and trash that would artificially inflate the weight.
Grading Accuracy
Fine yarns require a raw material with a low linear density to maintain strength and uniformity. Using the cut-and-weigh gravimetric method ensures that spinning mills select the correct grade for specific yarn counts. Coarser fibres identified through this test are diverted to heavy applications.