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Scoured wool is cored at the scour in either normal bales or high-density packs. The core samples are usually sealed on a bale by bale basis, although it is allowed to combine the cores from up to 7000 kg of wool. The sealed cores are transported to our nearest laboratory, where a sub-sample is taken for colour before the remainder is dried to determine the oven-dry mass percentage, and hence the regain. The regain is used to calculate the invoice mass at a standard level of regain (usually 16 or 17%) in accordance with IWTO-33.
Virtually all scoured wool exported from New Zealand is certified for:
- Conditioned mass
Because wool can absorb moisture up to 20% of its weight, invoicing is based on an agreed moisture content or regain - this is the conditioned mass.
- 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).
A large proportion is additionally certified for:
- Length after carding
A standardised method of simulating semi-worsted processing to estimate mean fibre length after processing.
Much of the wool is also tested for:
- Residuals
The amount of mineral matter and residual grease left on the fibres after scouring - an indication of scouring efficiency.
Additional tests that may be required include:
- pH
The acidity or alkalinity of the wool after scouring - important information for dyers.
- alkali solubility, and extent of bleaching
The solubility of wool in alkali is used to assess damage to the fibres. The extent of bleaching is important to some end uses.
- 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.
- bulk
The ability of fibres to fill space. Related to resiliance. 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.
- Detergent residuals
Wools intended for certain markets must be scoured with non-NPEO detergents. Further information can be found in Info-bulletin 5.10
- Mothproofing treatments
Information on insect-resist treatments can be found in Info-bulletin 5.11
- Sanitary reports
Shipments to certain destinations require an SGS Inspection Report confirming that any residual vegetable matter is non-viable. Other destinations may require verification of sanitisation procedures.
- Exports to Iran
Shipments to Iran require conformity assessment, which involves specialised testing. Further information may be found in TCO brochure (PDF 649 KB).
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.
Occasionally problems are encountered meeting specifications when scoured outputs are predicted using combination calculations on the greasy inputs. Info-bulletin 4.4 outlines some of the issues.
Guidance on the precision of standard testing may be found in Info-bulletin 5.9, which lists the published precision statistics for some of the common tests.
Pricing information, sample dispatch and minimum sample sizes can be found here.
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