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All greasy wool offered for sale at auction, or exported from New Zealand, is certified for:
- yield
Method for determining the amount of clean wool and vegetable matter contamination in a sample.
- mean fibre diameter
The average fineness of the wool (fibre thickness) - a primary determinant of wool value.
- colour
Measured as tristimulus values, but normally used to assess clean colour brightness (Y value), and yellowness (Y-Z value).
Other tests may be also requested, such as:
- staple length and strength
Average staple length, strength, and position of break are used to assess the performance of apparel wools in the worsted processing system.
- greasy length after carding
An alternative method of assessing average fibre length after processing, still in development.
- bulk
The ability of fibres to fill space. Related to resilience. Important for applications such as carpets, futons, insulating products.
- fibre curvature
A relatively new measurement available from OFDA and Laserscan but not standardised. Related to bulk, compressibility, crimp, and said to be an influence on processing.
- fibre diameter distribution
All wool contains a wide range of individual fibre diameters. Information about aspects of the diameter distribution may be important for assessing comfort and processing performance.
- diameter-length profile
Average diameter at increments along the length of wool staples may be important for managing sheep flocks, and in the future may assist in predicting processing performance.
- medullation
The presence of hollow fibres in wool and other animal fibres. Very important to appearance in apparel wools, causes uneven dye uptake, but desirable for some carpet types.
All of these tests can also be carried out on submitted samples, but in this case test reports are issued, which are not suitable for trading unless both buyer and seller agree.
Greasy wool samples can also be tested using fleece testing methods, which are low-cost methods specifically designed for animal selection purposes.
Guidance on the precision of standard testing may be found in Info-bulletin 5.9, which lists some published precision statistics for the more common tests.
Pricing, dispatch and minimum sample size information, can be found here.
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