Buyer guide · Fiber length
Cashmere Fiber Length for Spinning
Fiber length decides which spinning system a cashmere lot suits and how even the yarn will be. Worsted spinning needs longer, more uniform fiber, because combing removes the short fibers; woolen spinning is carded only and can use shorter fiber. Ask for mean length, short-fiber content and length variation, not just one number.
Woolen or worsted: why length matters
In worsted processing, fiber is carded, gilled and combed: short fibers, neps and vegetable matter come out as noil, and the remaining long fibers are drawn into tops. Woolen processing is carded but not combed, so it accepts shorter fiber and gives a bulkier, hairier yarn. This is why combed tops are made from longer lots, and why length uniformity matters as much as the average.
How dehaired cashmere length is measured
China's national standard GB 18267-2013 reports three length values for dehaired cashmere, all from a hand-arranged length diagram:
- Mean length (mm). The weighted mean of the hand-arranged fiber diagram. It is also part of the grade code: a lot coded DW54362 has a mean length of 36 mm.
- Short-fiber content (%). The share, by number, of fibers 15 mm or shorter.
- Coefficient of variation of length (%). How uneven the lengths are.
The standard rates short fiber against the mean length of the lot:
| Mean length of the lot | Short fiber, Class A | Short fiber, Class B |
|---|---|---|
| over 40 mm | ≤ 6% | ≤ 8% |
| 30–40 mm | ≤ 10% | ≤ 14% |
| under 30 mm | ≤ 15% | ≤ 19% |
The coefficient of variation of length is Class A at 50% or below and Class B at 54% or below. Anything beyond Class B is Class C.
Tops: Hauteur and Barbe
For combed tops, length is usually measured on an Almeter (IWTO-17). It reports Hauteur, the mean length weighted by fiber cross-section, and Barbe, the mean length weighted by mass. The Almeter measures fibers in a semi-relaxed state, so its values cannot be compared one-to-one with hand-arranged lengths. When you compare offers, compare like with like.
What makes dehaired fiber longer
Dehairing shortens fiber. A study of raw cashmere processing (McGregor and Butler, Textile Research Journal, 2008) found that white color, longer raw cashmere, greater fiber curvature, less vegetable matter and the absence of cotting were associated with more efficient dehairing and longer dehaired cashmere. Length is therefore decided partly at the raw-fiber stage, before the lot reaches the dehairing line.
What to put in your specification
- Target mean length and a minimum, for example "36 mm, not below 34 mm".
- Maximum short-fiber content (15 mm or shorter).
- Maximum coefficient of variation of length, if your process is sensitive to it.
- For tops: Hauteur and its CV, measured on the Almeter.
- The test method and lab, so our lot data and your check use the same basis.
Our typical dehaired lots have an average length of 34–40 mm; for tops, Hauteur is reported per lot in the test report. Send your length spec or ask for a tops sample.
Sources
- GB 18267 Cashmere (山羊绒) — hand-arranged length method and table 6
- GB 18267-2013 on China's national standards platform
- Woolwise (AWI) — Overview of early stage processing: worsted and woollen systems
- Woolwise (AWI) — Wool combing
- Woolwise — The measurement of Hauteur (H) and CVH
- IWTO Technology & Standards Committee — Metrology of the Almeter
- McGregor & Butler (2008), The effects of cashmere attributes on the efficiency of dehairing and dehaired cashmere length, Textile Research Journal
Ready to check this spec against a real lot?
Ask for a costing, a trial sample with test data, or an on-site inspection in China.