Cashmere Adulteration and the Test Methods That Survive a Dispute
Defending a cashmere claim demands LC-MS/MS proteomic proof tied to core samples that survive ISO 17025 cross-examination across two split lots.
Fiber Diameter Distribution
Geometric Spread
Dimensional spread of the widths of individual fibers within a sample defines the geometric spread known as fiber diameter distribution. In any batch of natural or synthetic fiber, the individual filaments are not identical in thickness, and the fiber diameter distribution provides a complete map of this variation. This data is typically presented as a histogram or a frequency curve that shows how many fibers fall into each micron category.
A narrow distribution indicates a very uniform lot, while a wide distribution shows a high level of variability. This metric is more descriptive than the mean diameter alone because it reveals the presence of exceptionally coarse or fine fibers that can affect the quality of the finished yarn.
Processing Behavior
Manufacturing performance is closely linked to the shape of the width distribution curve for the raw material. When a mill processes a lot with a wide fiber diameter distribution, the different thicknesses respond differently to the mechanical forces of carding and spinning. The coarser fibers tend to migrate to the surface of the yarn, while the finer fibers stay in the core.
This separation can lead to an uneven appearance in the fabric and can cause the yarn to have a different hand feel than expected. The mechanism of yarn breakage is often triggered by the thin spots created by a cluster of fine fibers or the thick spots created by coarse ones. To minimize these issues, spinners often blend multiple lots of fiber to create a more controlled and predictable distribution before starting the production run.
Uniformity Metric
Quantitative assessment of the spread is performed using high-speed optical or laser-based measurement systems. The fiber diameter distribution is characterized by several statistical parameters, including the standard deviation and the coefficient of variation. These numbers allow the laboratory to compare the uniformity of different lots and to detect the presence of unwanted coarse fibers, which are often called a coarse tail in the distribution curve.
Even a small number of fibers that are significantly thicker than the mean can have a negative impact on the comfort of the final garment. Testing laboratories must use standardized sampling techniques to ensure that the distribution measured is representative of the entire bale or shipment. The boundary of the analysis is determined by the number of individual fibers measured, with ten thousand fibers being a common target for high precision results.
Yarn Appearance
Aesthetic and tactile qualities of the finished fabric are a direct consequence of the width variation in the raw fiber. A fabric made from a lot with a narrow fiber diameter distribution will have a smooth, clear surface and a consistent color because the fibers absorb dye evenly. In contrast, a wide distribution can result in a fuzzy or hairy yarn surface as the coarser fibers are less easily incorporated into the yarn structure.
This fuzziness leads to a greater tendency for the fabric to pill during wear, which reduces the lifespan of the garment. High-end suiting and luxury knitwear require the most uniform distributions to achieve the softest possible hand feel against the skin.