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About New Zealand wool

Wool measurement

Why get wool tested?

Wool is measured before sale to provide an objective basis for establishing a price.

Sellers who have had their wool tested have a sound basis for establishing their selling price. They can negotiate from a position of strength.

Measurement also benefits buyers. If they are confident about the properties of the wool they are buying, they are in a position to offer their best price. If they lack this confidence, buyers must reduce the price they offer to allow for risk.

Objective measurement allows the buyers of raw wool to accurately assemble scourments and mill deliveries, reducing the potential for disputes with their customers.

Mills use test information provided by the exporter to achieve production efficiencies. It also enables them to specify their raw material requirements in precise, repeatable terms.

New Zealand wool

In New Zealand sheep breeds the fibre diameter, colour and length are comparatively uniform throughout the fleece.

In contrast, strong woolled sheep from many other parts of the world have mixed fleeces that are a combination of short, fine, crimpy wool and coarser, medullated fibres. Much of this wool is pigmented or discoloured.

For example, many NZ crossbred wools exhibit low coefficients of variation of diameter (35-45%), compared with measurements on wools of other origins (50-90%).


Yield (including vegetable matter content), fibre diameter and Colour are standard measurements for greasy wool. Sellers of fine wool are also encouraged to pre-sale test their wool for length and strength.

The results, which are arrived at through the use of international standard testing methods, are made available to the purchaser on test certificates. Additionally, for scoured wool, a New Zealand standard test for length after carding (to assist with early stage processing) has recently been introduced.

A test method for bulk has also been introduced and is available for either greasy or scoured wool. Sellers of hi-bulk wools are encouraged to have their wool tested for bulk.

Test houses

Wool can be tested in New Zealand at two accredited commercial test houses: The NZ Wool Testing Authority Ltd, Napier and SGS Wool Testing, Wellington.


The main certifiable fibre properties affecting the processing efficiency, product performance and value of wool are:


Greasy wool contains some natural contaminants, such as yolk (wax and suint, dirt, vegetable matter, and moisture, most of which are removed during scouring. It is the weight of clean wool (yield) that remains after scouring which is of interest to the processor.

Yield is the weight of clean wool, after the removal of impurities, expressed as a percentage of the greasy wool weight. Because it is used to estimate the quantity of usable fibre in a lot, it is a significant factor in wool trading, although it does not directly affect the actual processing efficiency of the wool.

Yield levels vary among breeds, between seasons and within the fleece itself. But in general, yield increases as fibre diameter increases. Average yields:

  • Merino: 68-72%
  • Mid-micron: 70-74%
  • Crossbred: 75-80%.


Typical yield values for NZ wool
Breed Fibre Diameter Full fleece Necks 1st Pieces Bellies 2nd Pieces & locks 1st Crutchings 1st Lambs
Merino 19 69            
21 70 66 62 60 51 60 66
23 71            
24 70            
26 71            
28 72 70 62 59 52 62 70
30 73            
31 74            
33 74            
Crossbred 30 75            
31 76            
33 77            
35 78 77 68 65 58 70 80
37 78            
38 78            
Lustre breeds 40 78 68   62   75 80
Drysdale 41 79         68 79

The yield from oddments can be as much as 10-15% less than the fleece from which they have been taken, with necks generally yielding the highest and second pieces and locks the least.

Wool is commercially traded using theoretical processing yields which make allowance for a small amount of dirt, wax and moisture to be left on the wool after commercial scouring. There are a number of common commercial yields in use on test certificates issued in New Zealand for the globally market. The IWTO Schlumberger Dry Top and Noil Yield is the standard trading yield used in New Zealand.

Care should be taken when using other commercial trading yields as these will differ from the IWTO Schlumberger Dry Top and Noil Yield values and so impact on wool value.

Vegetable matter

Vegetable matter, such as seed, small pieces of foliage, chaff or hay, adheres to sheep in the paddock and becomes embedded in their wool. Because it is not readily taken out during scouring, vegetable matter is an important factor to consider in wool purchasing, as increased levels of vegetable matter will affect both processing and product performance and therefore value.

Because fibres become entangled with vegetable matter, its removal during initial processing reduces yields. Vegetable matter that survives initial processing will also reduce downstream processing efficiency as it can cause yarn breakage and irregularity. Finally, vegetable matter in the yarn is generally undesirable as it spoils both the handle and appearance of fabric made from it.

IWTO Schlumberger Dry Top and Noil Yield includes an allowance for processing loss which varies according to vegetable matter conte4nt.

Mineral material

Particles of dust, dirt and sand picked up by sheep adhere to the greasy fibre in varying quantities, depending on grazing conditions, climate and wool type. Most New Zealand fleeces will average less than 2% mineral content, which will usually be removed during the scouring process.

Wools that are particularly dirty are termed "dull" or "sandy". In extreme cases, belly wool and skirtings may warrant the description "muddy".


Fibre diameter is the main determinant of spinning limit (the minimum number of fibres in a cross section that will permit a yarn to be spun), and consequently spinning efficiency.

While a degree of flexibility exists for coarse count yarns, finer counts require careful diameter selection to ensure correct spinning performance.

Fibre diameter also influences dyeing performance. Because fine fibres have a higher surface area to weight ratio than stronger fibres, when dyed, they give a much deeper yield shade in both yarn and product form.

Careful manipulation of fibre diameter in a blend can be used to achieve special effects, such as tweeds.

As a result of its importance to processing, fibre diameter is a major determinant of the price of wool traded on the world market.

There are three commercially recognised methods of determining fibre diameter in New Zealand:

  • The airflow method (IWTO-28)
  • OFDA (IWTO-47)
  • Laserscan (IWTO-12).

All these produce a measure of mean fibre diameter while OFDA and Laserscan can also give a measure of variability.


Fibre length primarily determines the processing system on which the wool will be spun, and consequently the properties of the yarn. This is because it affects the frequency of breakages during spinning and, as a result, influences yarn yields and maximum spinning speeds.

As with fibre diameter, length also has an important effect on yarn regularity, strength and extensibility, which in turn influence subsequent manufacturing efficiencies, product qualities and performance.

Fibre prices normally reduce as length decreases, a correlation which is most marked for fine and medium mid-micron and crossbred wools.

Length and strength

In terms of strength, wool is subjectively described as being either sound (strong) or tender (weak). Tenderness is caused by a reduction in fibre diameter at some point along the staple. This is a result of the seasonal growth pattern of wool or of stress suffered by the sheep, such as extreme climatic conditions, pregnancy or disease.

Length and strength testing for greasy wool is carried out using the IWTO-30 test method. This test gives staple length in millimetres and strength in Newtons per Ktex. The test is primarily used on fine apparel wools.

Length after carding (LAC)

Crossbred scoured wools may be tested for LAC using the NZS8719 test method. This test simulates commercial processing conditions and provides a processor a useful example of how a parcel of wool may perform in their plant.


New Zealand wools are well known for their uniformly good colour. Most of the clip is also free of black and pigmented fibre.

However, a wide range of wool types is produced, so a proportion of the clip shows some degree of discolouration. Poor wool colour may also be an indicator of the presence of other processing faults, such as tenderness.

Good colour is extremely important for yarn or fabrics that are to be dyed to pale pastel shades.

As dyeing is an additive process, it is not possible to produce a shade that is lighter than the original colour of the fibre. Also, the natural yellow component of wool is not light stable, so pale colours dyed on yellow wools may fade quickly.

Wool colour is expressed in terms of yellowness and brightness. These values are arrived at by analysing light reflected from a sample of scoured wool, in terms of the red (X), green (Y) and blue (Z) spectra. Brightness is equivalent to Y while yellowness is the perception of the difference between green and blue, (Y-Z).

In general, finer wools are brighter and whiter than stronger crossbred wools.

Specific types of discolouration:

  • Diffuse yellowness: Most apparent in late-shorn crossbred wools grown in warm, moist conditions.
  • Unscourable yellowness: Where longer woolled sheep are subjected to prolonged periods of warm, moist conditions. Prolonged periods of wetness may also cause confined bands of discolouration in the fleece
  • Natural staining: Although faecal material is usually scourable, unscourable breakdown products of pigments in grass may affect the colourfastness of some pastel shades in strong sunlight. Urine stains are unscourable and wool tends to be permanently discoloured if it becomes very muddy.
  • Storage discolouration: Greasy wool eventually discolours in storage; the more yellow the original colour, the sooner and more marked will be the change.

How wool is sampled – 'Cores and grabs'


Core samples and grab samples are used to provide descriptive information about the properties of the wool lot sampled.

The test laboratory uses the core sample to provide objective measurements of fibre diameter, yield, colour, bulk and vegetable matter content. The grab sample is used by appraisers to determine the wool properties that cannot be tested, such as degree of lustre, vegetable matter (VM) type, colour variability and, for those wools not length tested, the position of break.

Grab sample material can also be used to determine length and strength values.


A core sample is obtained by inserting a hollow tube into a conventionally packed wool bale. The tip of the tube is sharpened to allow the tube to cut out a cross-section of wool fibres from within the bale. The tube is approximately 20mm in diameter and long enough to collect a sample from almost the full length of the bale. The core provides a representative sample of the wool for most of the fibre properties required by the test lab. It cannot, however, give an indication of fibre length since the tube cuts most fibres to about 20mm in length.

Coring can be carried out manually, but for certification purposes is normally done using a mechanical system that weighs and cores the bale at the same time.


Grab samples are obtained by inserting a grab head into the side of a conventionally packed wool bale. The grab head is a device that resembles a large pair of pliers with jaws designed to grab and extract a section of wool from within the bale.

The grab sample provides a representative sample of the wool for visual assessment. As the grab sample extracts whole sections of the fibres within a bale, the sample can also be used to give objective length measurement information.


SGS Wool Testing –


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