Fleece Testing Reporting Functions
is an integral part of the Merino Wool Industry and affects all participants from the commercial grower to the end user who wears the finished garment. Its affect ranges from management problems such as fleece rot and fly strike, through sale price due to dust penetration, tip weathering and doggy wool, to prickle in the finished garment.
Selection for heavier wool cuts tend to increase fibre diameter variation.
FIBRE DIAMETER DISTRIBUTION
is directly related to:-
Staple structure and Style (arrangement of fibres within the staple).
FIBRE DIAMETER DISTRIBUTION
is the distribution, or number, of fibres of each diameter in any given wool sample. When measured, it enables the degree of fibre diameter variation, or uniformity, to be assessed.
Good staple structure requires fibre diameter uniformity. Evenly sized fibres grow and crimp in unison to give an even, distinct crimping pattern. This gives wool true style and character.
Poor staple structure has considerable fibre diameter variation. Unevenly sized fibres produce crimps of uneven length and depth which give rise to a disrupted crimping pattern and feathery tip.
Resistance to fleece rot and fly strike is very dependent on good staple structure which naturally facilitates the rapid draining and evaporating of moisture which may enter the staple.
A blocky tip does not necessarily indicate evenly sized fibres!! It is often formed after shearing when copious wax cements the tips of the wool fibres together which creates the blocky surface and disguises any naturally feathery tip.
Feathery tips allow substantial dust penetration. They also weather and tend to break and become noil during processing.
Handle is very dependent on fibre diameter distribution.
Poor Handle is largely attributable to fibre diameter variation (these wool’s deteriorate in appearance and become stronger microning).
The Histograms and measurements are provided as a guide to assessing the comparative wool quality and average micron of this group of sheep.
C of V can also be used as an efficient indicator of staple strength. Low C of V of fibre diameter, lead to a high staple strength.
It measures the "tail" of the FD Histogram. These fibres disrupt the internal staple structure and are the framework for feathery tips. In severe cases, they can be pre-emptive of the future increase in the average micron of that sheep.
The coarse edge qualifies and fine - tunes the C of V assessment.
%FIBRES >30 INFO
% FIBRES <15 INFO
The spinning qualities of wool are enhanced by a low coefficient of variation, which enables the wool to be processed at standards less than the given micron.
For e.g. a 20 micron wool with an 18% C of V, has the spinning qualities ( or fineness) of a 19 micron wool. The same 20 micron wool with a 29% C of V, would have a spinning quality (or fineness) of 21 micron.
FIBRE CURVATURE INFO
What use is curvature?
Curvature relates strongly to staple crimp characteristics, particularly crimp frequency - for as frequency increases, the fibres are increasingly curved. But curvature is not the same as character (staple crimp definition), which is a measure of how well aligned fibres are. Fibre alignment and thus staple crimp definition does however relate to the CV of curvature, since it is physically hard to align fibres differing in curvature. Figure 1 illustrates these points:
Recent scientific evidence confirms that wool fibre curvature influences processing efficiency, particularly during topmaking and spinning operations, yarn thickness and evenness and fabric thickness, handle and quality.
Measurements of fibre curvature have the potential to have a major positive impact on the ability of our wool to deliver to consumers the soft, lightweight and easy care fabrics consumers increasingly demand.
In raw wool, OFDA measurements of curvature commonly range from 60 o/mm, for wools of low crimp frequency, up to around 130 o/mm, for superfine samples. The standard deviation of curvature on the OFDA commonly ranges from around 40 - 100 o/mm, generally increasing as the average curvature increases, and as staple crimp definition decreases.
Measurements of fibre curvature could therefore be a useful means of identifying and specifying wools of particular style, such as Superfine wools, or the target wool type of the Soft Rolling Skin Sheep selection system. The latter is characterised by a low average curvature relative to the average diameter, as well as low CV’s of both diameter and curvature.
Higher rainfall areas benefit from lower figures.
REMEMBER do not neglect the basic need for wool production - select for productive wool cutters and frame, then fine - tune the wool to suit your own environment.
A simple tool for assessing fibre diameter / fibre curvature combinations on adult wool (greater than 2 years old) is shown in the graph below. This roughly defines the combinations for "true-to-type" and potential Elite or SRSä wools.
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