Whitish Merino wool with good crimp and high clean yield.

Estimated reading time: 6 minutes

It is well known that commodity prices generally decrease in real terms. Therefore it is imperative that wool producers understand the assessment system with the terms and references that is applied to value their wool clips.

The Australian Wool Exchange Identification Document (AWEX-ID) assessment system is used by most brokers in South Africa to type, measure and analyse the performance of the clip in an objective and subjective way to deem it comparable to international standards. This system ensures that the South African clip is comparable to its Australian counterpart that sets the international wool price indicator.

“This classification is applied because it is a powerful tool that ensures quality information to the broader wool industry and consumers don’t need intensive training to understand the codes. It also supplies useful information for effective classing and typing. With this data at hand producers are able to adapt management systems and to evaluate breeding directions and genetic progress in an effort to maximise the income from their clip,” says James de Jager, manager of fibre at CMW.

Categorises the wool

This spreadsheet of information, supplied by the brokers to producers after their clip is assessed and before it is sold, categorises and identifies the wool into:

  • Different breeds (e.g. AS – Superfine Merino; M – Merino; X – non-Merino; D – downs and C – carpet).
  • Different wool categories (e.g. W – hoggets and lamb wool; L – carding lambs, 50mm and shorter; U – dead and blowfly infested wool; K – wool shorn from pelts, etc).
  • Different wool lines (e.g. F – fleece lines that include back and neck wool; P – fleece pieces such as neck skirtings, breeches and long sweaty lox; B – bellies, etc).
  • It also objectively measures other characteristics including style, clean yield, tensile strength, length and fibre diameter, among others.

Better style wool produces less noil (combed-out bits) and provides a better hauteur (fibre length in tops), while poor quality wool is inclined to felt easier in the washing process. Style is valued on a scale from 1 to 7 and the South African clip generally falls between 4 and 7 on this scale where 4 is considered superior spinning material, 5 good and 7 inferior quality.

Financial benefit

Properties that influence style include uniformity of length, dust penetration, weathering, uniform and obvious crimp and staple density. Crimp has a great effect on the fineness of the wool and determines the quality of the end product.

Good style increases the adhesive and spinning properties of the fibre. It also adds to the elastic resilience of the final fabric and renders it light and warm. Under-crimped wool has a greater inclination towards felting, doesn’t drape well and has low crease resistance.

“There is great financial benefit in producing good spinning types and the price difference between good and poor quality tops is marked,” says Robert Scott, manager wool and training of BKB.

Creamy Merino wool, slightly under crimped but with good staple and clean yield.

Clean yield is also measured objectively and in technical terms assesses how much clean wool would be left if one kilogram of wool is washed. Urine stained or pigmented wool has a negative impact on prices and farmers are encouraged to crutch their animals at least 12 weeks prior to shearing especially if they mate for cross breeding.

Floating kemp is a phenomenon often found in the Merino clip and this condition arises when Dorpers or Persians run together with Merinos. If they share the same facilities they contaminate the Merino wool with kemp (unmedullated hollow fibres that don’t absorb dye and which are completely undesirable in the final product).

High clean yield

A yellow hue in wool often indicates colouring due to age or wool that has an oil-flow tendency, while green could indicate fungus infected wool. A high clean yield favours buyers and a premium is set on uncontaminated wool that is free of coloured fibres, lox, kemp and foreign objects.

But probably by far the most important price determinator is fibre diametre or micron, which constitutes 70 to 80% of the value of the tops. This can be determined by an airflow, laser scan or Ofda test. The laser scan and Ofda method can also determine the coefficient of variation which defines the comfort factor.

The comfort factor is measured by the percentage of wool in the clip that exceeds 30µ (micron). So, if the clip has a comfort factor of 95% it means that 5% of the clip has a micron value in excess of 30µ. Wool with a fibre diametre higher than 30µ has a high irritability factor and will not be tolerated close to the skin.


Tensile or staple strength determines wool’s ability to withstand processing and is the second most important price determinator. There seems to be a 0,36% heredity component to tensile strength and a genetic correlation between the coefficient of 0,58% in variation of micron and tensile strength.

In other words if you use rams with a low coefficient of variation of micron, you are likely to breed animals that produce a more sound wool. Weaker wools produce more waste in carding and spinning and may be used for production of felt, or combined with other fibres.

Longer fibre

“Tensile strength is measured in Newtons per Kilotex and the percentage breaks in the tip, middle and basis are recorded. A premium is paid for high Newton wool as it provides a longer fibre in the hauteur that enables spinners to complete the spinning process faster.

“Fine wool attracts price premiums at auctions but are much more susceptible to breakage as a result of low staple strength or ‘tender’ wool. Tender wool receives discounts that can range from 3% to up to 30%. This can greatly impact on wool income and it is advisable to eliminate sheep where the comfort zone is below 97%,” says Robert.

“Buyers are inclined to discount wool that is below the strength of 35N/ktex and pay premium prices for wool above 38N/ktex. This makes staple strength an important contributor to the final price of the wool clip. Staple strength of wool is difficult to predict and manage.

Break in the fibre

“Poor staple strength, or ‘tender’ wool, occurs when there is a break in the wool fibre due to drought or other animal health conditions that induce fever. This could also be caused genetically by high coefficient of variation of micron and length. The break is usually at the point of minimum fibre diameter, or when there is a rapid change in the diameter of the fibre.”

Wool that is slightly tender will be described as W1 with subjective testing and will have an N/ktex of between 25 and 30. W2 is a tender wool that will test between 21 and 25 and W3 is very tender with an N/ktex of less than 21.

“Classing wool according to the National Wool Classing standards ensures that the reputation of the South African Wool clip is ensured. Buyers are willing to pay a premium for the national clip because it is well classed and well assessed. They have faith that they are buying what is catalogued,” concludes James.

The wool trade, the wool buyer, the wool processor and everyone who buys wool should be able to rely on these standards and wool producers should use the results of the objective and subjective tests to improve their clips while assessing their breeding policies. – Linda Henderson

Contact James de Jager on 082 778 9931 and Robert Scott on 041 503 3111 for more information.

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