Yarn Twist
Definition
The number of turns per unit length and the direction of twist in a yarn. S-twist and Z-twist are the two standard notations, and the twist direction can survive transfer.
- Measured as
- Turns per unit length
- Directions
- S-twist and Z-twist
- Forensic relevance
- Twist direction can survive fibre transfer
- Examination method
- Low-power microscopy
Common questions
How does yarn twist direction help link a fibre to a source?+
S-twist and Z-twist are a manufacturing choice that stays consistent within a given yarn or garment, so a recovered fibre showing the same twist direction, count and character as a known source is one more point of correspondence, though twist alone is not individualising and is assessed alongside colour, cross-section and composition.
Can twist direction be identified from a single loose fibre fragment?+
It depends on the fragment; twist is a property of the spun yarn as a whole, so a very short or badly damaged fragment may not preserve enough of the yarn structure to determine twist reliably, and examiners note when twist could not be assessed rather than guessing.
Related terms
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- Microspectrophotometry (MSP)
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- Pyrolysis GC-MS
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- Tape Lift
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