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Reading Fibre Test Results

Paul Vallely - Australian Alpaca Fibre Testing 

Introduction

In recent years, the world's Alpaca industry has made significant progress towards establishing itself as a supplier of raw fibre to the textile and craft markets. Although commodities have suffered under the weight of global economic hardship, alpaca fibre is witnessing potential as an emerging luxury fibre within the luxury garment and environmental/welfare conscious markets.

At the 2008 National Alpaca Fibre Seminar held in Australia, presenters from processing and garment manufacturing firms revealed a growing demand for quality alpaca fibre. This was further evidenced at the World Alpaca Conference held in Oxford, UK in 2012.

Alpaca breeders at both these events were told that although a range of fibre types would be required for various product ranges, growers needed to focus on ‘key market drivers’. In other words, growers needed to produce fleeces that exhibited those traits sought by the respective markets in order to secure supply opportunities and reap price premiums.

For breeders pursuing craft and/or value adding objectives, the principle of producing fleeces that meet key fibre traits still apply.

Objective fibre traits such as average fibre diameter, variation of fibre diameter, incidence of coarse fibres (comfort factor) and staple length provide clear expectations on processing performance and eventual yarn/fabric quality, and therefore, were critical in pursuing opportunities for supplying fleece.

Similarly, objective traits also play a key role in the quality of home spun products, although the degree of importance of the relevant traits may differ compared to those preferred by commercial markets.

It should be remembered that visual traits such as colour, clearly have some influence on price paid or craft outcomes, however, they are not the subject of this article.

Monitoring objective fibre traits using fibre measurement, therefore, makes a lot of sense. It allows fleece growers the opportunity to identify alpacas that are likely to produce the more valuable or preferred fleeces. More importantly, it also provides an insight into the genetic potential of breeding stock to produce progeny capable of growing these premium fleeces. 

Both science and practical experience have proven that fibre measurement is the most effective and efficient method of monitoring fibre traits. The following information is provided to alpaca breeders as a guide to embarking on or maintaining a fibre monitoring program.


How to Take a Fibre Sample

The main points to note regarding mid-side sampling are as follows:

1 Always use the same sample site. This will enable you to effectively compare results. The preferred and most commonly used site is the mid-side. The mid-side is located half way between the fore and hind leg and half way down the body mass. The left hand side of the alpaca is normally used for the mid-side as the right side is exposed to judges when showing.

2 To breed for reduction in variation of fibre diameter across the fleece, three sample sites may be used. In this case, the mid-side, the shoulder area and the pin-bone (hip) are recommended.

3 For OFDA2000 testing, the size of the fibre sample needs to be only the width of two fingers.

4 When cutting the sample from the alpaca, ensure the sample is taken as close to the skin as possible so that a complete test analysis can be conducted on the whole length of fibres.

5 Place the sample in a paper bag. If a plastic bag is used, the bag should not be sealed as condensation build-up can distort the fibre measurements. Record the alpaca’s name and/or tag/IAR number on the bag.

6 Send the samples to your preferred fibre test provider.  

Interpreting Test Results

The following is a list of commonly used terms with fibre testing.

Micron: Unit of measurement for describing diameter of fibre. 1,000 microns = one millimetre. Fibre diameter is the single most important fibre trait with regard to commercial processing. It is also one of the most heritable fibre traits

Mic Dev: (Micron Deviation) The extent to which a sample's average micron deviates from the herd’s average.

SD: (Standard Deviation) This shows how much fibre diameter variation there is within a fibre sample. Within one fibre bundle, the individual fibres will vary by about 20 to 25 microns. For instance, one fibre bundle might have individual fibres with diameter of, say, 15 microns, while it will also have fibres with diameter of, say, 35 microns. 

The range in diameter within a fibre bundle from an alpaca, will generally be repeated over that alpaca's saddle area.

In statistical terms, a standard deviation is how far from the average you need to go to capture about two thirds of total variation within the sample. In fibre testing, we use SD to show us the degree of variation in microns.

For example, a fibre sample has an average diameter of 20.0 microns with a SD of 5.0 microns. In this case, about two thirds of the fibres in the sample are between 15.0 and 25.0 microns (5 microns either side of the average of 20 microns). The lower the SD, the less variation in fibre diameter.  

SD is the preferred measurement for determining fibre diameter variation on individual animals. Alpacas with low SD generally have a softer handle, greater tensile strength, and often have less variation over the fleece area. SD is highly heritable.

CVD: (Coefficient of Variation of Diameter) Is the standard deviation expressed as a % of the sample’s average. For example, if the average diameter is 20.0 microns with a SD of 5.0 microns, the CVD is 25.0%. (5/20 x 100) 

CF: (Comfort Factor) Percent of fibres in a sample that are equal to or less than 30 microns. Fibres greater than 30 microns are generally responsible for the prickle sensation when worn next to the skin.

CEM:  (Coarse Edge Micron) The range in microns between the average diameter and the coarsest 5% of the sample. This is a good tool for monitoring problematic primary fibres.

<15%: The percent of fibres in a sample less than 15 microns.

CRV: (Fibre curvature) expressed in degrees/millimetre. Generally, higher curvature is associated with higher crimp frequency.

SF: Spin Fineness: Calculation using micron and CVD to represent the spinning quality. 

Micron Profile: A graph showing the variation of fibre diameter along the staple. Can be used for analysing the nutritional intake over the growing season. The graph is read from left to right.

Histogram:  A bar graph depicting the distribution of fibre diameter for the sample.  On the vertical (y) axis of the graph is the micron of the fibre counts. On the horizontal (x) axis are a series of numbers which represent the frequency of distribution of those fibres counted. 

SL: Staple length expressed in millimetres. (Staple is another term for fibre bundle)

Max Mic. The broadest point along the staple, expressed in microns. 

Min Mic. The finest point along the staple, expressed in microns.

FPFT: (Finest point from the tip) Expressed as millimetres from the tip to the finest point in the staple. An indicator for the ‘point of break’.

MFE: (Mean fibre ends) The average fibre diameter of the fibre ends [tip and base] expressed in microns.

Hauteur (predicted):  The estimated length of fibres after scouring, carding and combing.

Example of two sets of results including data, histograms and micron profiles. Analysis of the results follows below the examples.

 



Analysis of Two Fibre Test Examples (Above)

Top Example (6B46)

The average fibre diameter is 15.8 micron. As can be seen on the histogram, most of the fibres are centred close to the mean diameter. Almost all fibres are between 9 microns and 28 microns, (range of 19 microns). This alpaca has very low variation of fibre diameter, and consequently has a low SD of 3.4 microns, (2/3 of fibres are between 12.4 microns and 19.2 microns). As all fibres are below 30 microns, the Comfort Factor is 100%. 

The micron profile shows a relatively flat profile indicating stable level of nutrition passing to the fibre follicles. The profile shows the average diameter of the fibre staple starting at almost 17 microns at last shearing (left side of profile), then finishing at about 16 microns when the sample was taken.

The results indicate this sample is from a superior animal, capable of producing premium ultrafine type fibre.

Bottom Example (6Y40)

The average fibre diameter is 26.3 microns. The histogram shows high variation of diameter of individual fibres, ranging from 13 microns to 48 microns, giving a range of 35 microns. For this reason the SD is 5.5 microns, (2/3 of the fibres are between 20.8 microns and 31.8 microns). Note that the CV is 20.8%, which is lower than the above alpaca at 21.4%. The reason for this is the difference in fibre diameter.

The comfort factor is 82%, meaning 18% of fibres are greater than 30 microns. The fibre from this alpaca would likely have a prickle feel if worn next to the skin.

The micron profile shows the level of nutrition falling dramatically about half way through the growing season, before rebounding to almost its initial diameter. This might be a result of worm infestation, dry conditions or ill health followed by a return to lush or healthy conditions. The fibre would likely be tender at the finest point on the profile.

This alpaca would be regarded as producing inferior fleece by commercial standards.

Micron Blowout

Many growers lose faith in their animals once they receive a test report showing a high fibre diameter result . The fact is, the animal might be capable of producing premium type fleeces, however, it may have been subject to overfeeding. 

During 2006, Australian Alpaca Fibre Testing conducted over seven thousand alpaca fibre tests. The average micron for these tests was 25.1 microns. A high percentage of these tests were on samples from first or second fleeces.

The average range in fibre diameter along the staple was 4.8 microns. This represents how much the fibre changed in diameter over the growing season. This variation is caused mainly by changes in nutritional intake. High nutrition causes the fibre to broaden. Overfeeding high quality hay or grain has often been the cause of much anguish when the fibre test results are revealed.

With many of the alpacas we tested, the fibre diameter blew out by more than 10 microns. In one year, an alpaca blew out by a staggering 19.2 microns – starting at 18.1, and finishing with 37.3 microns at the point of shearing. 

A random selection of 100 test results from 2006 showed about 20% of fleeces to be under 20 microns at one point, but finished with an average fibre diameter of over 26 microns. 

Obviously, feeding regimes for pregnant females or developing crias might require high nutrition irrespective of impact on fibre diameter. Furthermore, I’m not suggesting you keep your alpacas just one step away from needing life-support systems to survive. The message is to find the right balance. 


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