INTERNATIONAL WOOL TEXTILE ORGANIZATIONTECHNOLOGY & STANDARDS COMMITTEE
By V. E. Fish, T. J. Mahar & B. J. Crook
University of New England
Armidale, NSW, Australia
This is a long, highly technical review of the current situation concerning the measurement of fiber curvature. Based on its strong association with crimp frequency, wool fiber curvature measurement holds promise as a further specification, which can be used to add value to wool in production, trading and processing.
The authors make the point that curvature/crimp is important to textile manufactures and note that synthetic fiber manufactures add crimp to their inherently straight fibers and filaments to improve the bulk density of their textile products. For wool, staple crimp frequency has been a means of quantifying the bulk density of wool for many years. Subsequently, more direct measurements of bulk density were developed – Resistance to Compression (RC) measurement in Australia and South America, and the Bulk measurement in New Zealand.
The article speaks to the benefits of crimp in finished goods and its relationship to handle.
Staple Crimp Frequency has been shown to be related to wool production and the performance of wool in processing and in determining the quality of the wool textile products, e.g. tops, yarns and fabrics. Swan found that a reduced crimp frequency was associated with higher fleece weight, i.e. a genetic correlation of -0.21. A number of researchers have reported variously on the beneficial effects of low crimp frequency compared to high crimp frequency on processing performance to top (lower fiber entanglement, longer Hauteur) and on top quality (lower nep counts). Similarly, a low crimp frequency has been associated with improved spinning performance and higher yarn quality in research trials in both South Africa and Australia. Yarns produced from wools of low crimp frequency were spun with fewer ends-down and were stronger and more even than equivalent yarns from high crimp frequency wools. Similar processing benefits have been reported for wools with low RC compared to wools with high RC values.
It should be noted that when wool processors refer to highly crimped wools they are discussing 22 – 32 crimps per inch, however crimp in fine Merino is 12 – 14 crimps per inch. (See: Ideal Alpacas from Myth to Reality.) Highly crimped alpaca fiber is rarely more that 10 crimps per inch. For soft handling, highly crimped alpaca is ideal while a moderately crimped sheep’s’ wool is desirable.
I warn you; this is a long technical article. For those of you who want to get to the bottom line here are the conclusions.
CONCLUSION
Based on its strong association with Crimp Frequency, wool Fibre Curvature is a measurement that has potential to add value to wool from its production through the processing chain to a finished wool fabric.
Fibre Curvature is less stable than other comparable raw wool characteristics such as Mean Fibre Diameter, Staple Length and Staple Strength. Despite this apparent instability, Fibre Curvature measurements have demonstrated strong agreement between the two commercial instruments, LASERSCAN and OFDA.
Prior to any standardization of Fibre Curvature measurement using either the LASERSCAN or OFDA instruments, work is required to determine appropriate calibration, sampling, preparation and testing procedures. It is hoped that the procedures currently in place for the measurement of diameter (IWTO- 12-98 and IWTO-47-98) will require little or no modification in order to accommodate Fibre Curvature measurement. However, until an adequate definition of equilibrium conditions necessary to stabilize the "inherent" or '"as is" Fibre Curvature prior to measurement is developed, there can be no certainty that this will be the case.
Until this work is completed, the use of the Fibre Curvature measurements provided by both instruments should be approached with caution. Click here to read more. 
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