Fibre Curvature - what is all the fuss about?
WHAT IS CURVATURE?
Wool fibres typically have a wave or crimp pattern as illustrated below. Wool staple crimp can readily be seen in wools with good character. Even in wools with poor character, or clarity of staple crimp, the individual fibres will generally have a crimped shape. Fibre Curvature is related to crimp.
Fibre Curvature is a measure of crimp using fibre snippets. It is measured by a LASERSCAN or by an OFDA in units of degrees/mm.
The scale drawing below illustrates wools of Low, Medium and High Fibre Curvature.
SOME TYPICAL VALUES:
A 30µm Crossbred fleece wool typically has a Low Curvature and a broad crimp.
The crimp frequency is approximately 2 crimps/cm.
A 21µm Merino fleece wool typically has a Medium Curvature and a medium crimp.
The crimp frequency is approximately 4 crimps/cm.
A 16µm Superfine Merino fleece wool typically has a High Curvature and a fine crimp.
The crimp frequency is approximately 7 crimps/cm.
WHY IS CURVATURE IMPORTANT?
Due to curvature’s relationship to crimp, for wools of the same diameter, it might be expected that Low Curvature is associated with:
Wool Production
- Longer Staple Length; and
- Higher Fleece weight.
Wool Processing
- Longer Hauteur (fibre length) in top;
- Less noil and card waste;
- More even yarns; and
- Smoother fabric handle.
OFDA or LASERSCAN WHICH INSTRUMENT SHOULD BE USED?
Research shows an excellent correlation between OFDA and LASERSCAN curvature results:
AWTA recommends the use of LASERSCAN for cost considerations (LASERSCAN is cheaper than OFDA).
Although LASERSCAN is recommended, AWTA will conduct an OFDA test if requested.
However, users of this information need to be aware that both the OFDA and LASERSCAN cannot be calibrated for measuring curvature, and that the measurement is also dependent upon the method used to prepare the sample. Therefore, all curvature measurements must be viewed with caution. For further information refer to the May 2000 issue of AWTA Ltd's Newsletter.
Download a PDF version of this FactSheet.
FURTHER INFORMATION
Ian Ashman
General Manager Customer Relations
AWTA Ltd
Ph: 03 9371 4103
Fax: 03 9371 4191
Email: ian.ashman@awta.com.au