Company Services

NZWTA Ltd offer a range of wool testing services to the wool industry.  These tests are available on individual animals (fleece tests), as tests on greasy wool, and on scoured wool ready for processing.

Fleece Measurement on individual animals

Samples usually taken from the “mid-side” of individual animals can be measured for the following characteristics:

• Fibre diameter (mean fibre diameter & diameter distribution)
• Staple length and strength
• Medullation and fibre curvature
• Washing yield
• Colour
• Bulk

Greasy Wool Testing

Core samples taken from bales of greasy wool can be tested for yield, vegetable matter (VM), fibre diameter, colour, bulk and medullation.  Grab samples are tested on ATLAS to establish staple length and strength, and the position of break.

Where sampling is not done to full IWTO requirements, the results are reported as Guidance Reports.  These results are reported as IWTO Test Certificates, where the lots are sampled and tested according to the IWTO Core Test Regulations and Test Methods. 

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Scoured Wool Testing

Individual lines of wool are put together and scoured.  The resulting scoured wool is tested in a Comprehensive Scoured Wool Package.  This involves testing core samples of wool for:

• Conditioned Weight (moisture content),
• Yield and Vegetable Matter content,
• Colour, and
• Residual Grease.

Additional measurements can be made for:

• Core Bulk,
• Fibre diameter distribution (from Laserscan or OFDA),
• pH,
• Medullation, and
• As is Colour.

Length of scoured wool is measured using the “Length after Carding” test which uses a sample drawn by a mechanical grab sampler.  This test can also predict the losses from carding known as the “Card Waste”.

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What is involved in these tests?

At the time of sampling for testing, the bales are weighed to give a gross weight of the wool including the pack and all the impurities in the wool.  The bales are core sampled, and from the core sample the following tests can be performed according to the test methods described in either IWTO test methods or in New Zealand Standards.  Some of these tests are:

Yield Testing

This is the weight of clean wool (after the removal of all impurities), expressed as a percentage of the weight of the greasy wool.  These impurities can be natural such as grease or suint (sweat), or acquired such as seed and burrs, along with dirt and other mineral matter.  In addition wool naturally absorbs moisture and this can vary from day to day, depending on climatic conditions.

Core sampling techniques have been developed to give a laboratory sized sample that is statistically representative of the bales being tested.  By measuring these impurities in the laboratory an accurate assessment of the wool base can be produced which will give a true reflection of the bale contents.  The yield test gives a measure of the wool base, the vegetable matter content plus a series of calculated yields related to processing performance.

Fibre Diameter

Wool fineness is related to the ultimate spinning count of the worsted yarn which could be produced from the wool.  The number of single worsted skins which could be spun from a pound of wool was referred to as the quality number of the wool under the Bradford count system.  This used crimp frequency in the staple as a basis for prediction.  However, this does not accurately reflect the processing capabilities of the wool.

With commercial pressure, changing machinery and improved technology more accurate measurement is now required.  The introduction of the Airflow meter started a revolution in wool measurement which over the years has replaced the old Bradford count numbering system with the fibre diameter measured in micrometers or microns.  (One micron is equal to one millionth of a metre.)  This technology gives a quick accurate and stable test which has been adopted as an IWTO (International Wool Textile Organisation) standard and is used internationally as a basis for trade.

New methods using “Laserscan” & “OFDA” technology provides fibre diameter distribution information as well as the mean fibre diameter measurement which is important in processing.  These new instruments are more accurate, more precise, more stable, and are likely to become the future basis for all trade.  Laserscan is already the basis for trade for Merino wool.

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Colour

The purpose of colour measurement is principally to assist in dyeing wool during processing.  As dyeing is an additive process it is therefore impossible to dye wool lighter than its original colour.  The increasing demand for lighter shades in carpets and fabrics has prompted the development of an international standard for the measurement of colour in wool.  Processors also want to match wool to repeat colours between batches.

The reflectance of light is usually measured in three bands in the visible spectrum.  Red  orange are referred to as the X value, yellow green as the Y value and blue/indigo violet known as the Z value.  These are known as the tristimulus values.  The lower the value the less reflectance (the more the light is absorbed).  In wool the X and Y values are very similar and for this reason the X value can generally be ignored.  From a valuer’s point of view the brightness of wool and the yellowness are important.  The Y value represents the brightness of the wool and the difference between the Y and Z value (Y-Z) is used as an indicator of the yellowness of the wool.

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Wool Bulk

This test determines the ability of wool to fill space and recover after repeated compression.  It is significant in determining the thickness of the yarn and ease with which it can be processed, and the amount of yarn required to make a product look “full”.  Core Bulk is measured in cubic centimeters per gram.

How do we measure length?

For greasy wool a test has been developed (especially for combing wools finer than 30 microns) to measure staple length, staple strength, and position of break.  The test is carried out on an instrument called ATLAS (Automatic Tester for Length and Strength).  The test uses a sample drawn from the grab sample, not the core sample, and measures the length of the sampled staples, their strength, and the position at which the staples break.  It allows the prediction of processing length of a line of wool.  Wool processors have been paying premiums for wool which has this information available as it enables them to set their processing equipment and production output to maximise their performance.  Growers are using this information to market their wool and to modify any management practices which have impacted on the value of the wool they are producing.

Length testing for scoured wool has been developed for New Zealand wool using a process called “Length after Carding”.  This process involves sampling mechanically scoured wool from each bale before packing, and using a standard card to prepare a carded sliver.  A “fibre draw” from this sliver is read on an Almeter to give a certified test result for Barbe length.  Additional information (not certified) is provided for the distribution of the fibre lengths within the sliver.

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For contact details for NZWTA personnel please refer to CONTACTS.