Production

Australia is the largest wool growing country in the world, with 426 million kg of wool shorn in 2006/2007. Factors that influence production levels include: sheep husbandry, health of the land and methods of wool harvesting.

Sheep Husbandry

Practicing good sheep husbandry is an essential element to produce a good quality fleece, this includes:

Managing internal and external parasites such as worms and lice
Stocking paddocks at the correct stocking rate
Avoiding grazing areas with heavy grass seed or burr contamination
Managing the risk of flystrike which may include tail docking, mulesing, crutching, chemical use

Shed Management
Good shed management is vital for quality control of the wool clip, both the wool grower and wool classer have a number of responsibilities which include:

The wool grower - a clean shed free of contaminants, an adequate working facility, AWEX approved wool packs and providing information on the mobs of sheep to be shorn to the wool classer.

The wool classer - ensuring each fleece is carefully skirted, separating cast fleeces from the main line, supervising shed staff to ensure lower lines and oddments are correctly prepared and bales are accurately pressed, preventing contamination occurring during shearing.

Both the wool producer and the wool classer must sign the Classer's Specification to confirm that the clip has been prepared to the AWEX standards.

Wool Harvesting
There are two main methods of wool harvesting:

Traditional shearing
Biological wool harvesting

1. Traditional Shearing
Shearers remove the fleece from the sheep in a series of rapid actions. The fleece is left flat on the shearing board for a wool handler to collect. The fleece is thrown upwards and outwards onto a wool rolling table for skirting and classing.

Shearing is organised in a number of ways depending upon the property and the number of sheep to be shorn. A smaller property would normally employ a shearing team (including shearers, wool handlers and wool pressers) and the owner would do the wool classing using their owner/classer AWEX classification. On larger properties and pastoral stations it is common that a shearing contractor would be employed to provide all the necessary staff including the wool classer.

2. Biological Shearing
Bioclip is a biological process for removing the fleece that has been available to wool producers since 1998. The science behind Bioclip was developed by the CSIRO Livestock Industries unit over the last 20 years.

Sheep are fitted with a retaining net and given a single vaccination of a naturally occurring protein, which causes a natural break to occur in the wool fibres. A week later the fleece is shed as a whole inside the net, and is removed by hand - in a process known as doffing.

The wool begins to grow again after 24 hours and the sheep can be marketed within seven days of treatment. The process minimises sheep stress and eliminates the labour of traditional shearing, reduces variability in wool fibre length, increases carding yield and hauteur and decreases wool lost as noils during combing.

Skirting and Wool Classing
Skirting involves removing all inferior wool from the fleece and is important for good clip preparation. The fleece is then rolled up and presented to the wool classer.

Shorn wool is classed into five main categories:

Fleece - the bulk of the wool from the body of the sheep.
Pieces - coloured and frib or sweaty edges from the fleece.
Bellies - wool from the belly region of the sheep.
Crutchings - wool from the tail section of the sheep, which may contain urine or dung stains.
Locks - short wool created by the mechanical shearing process.

Any wool that is of poor colour, shorter, weaker or unusual is separated from the main lines. The wool classer will describe lines of wool using bale descriptions such as AAAM, AAA PCS and BLS.The classing of wool is described in the Code of Practice for the Preparation of Australian Wool Clips, published by the Australian Wool Exchange.

Some wool producers use on-farm fibre testing equipment to more accurately class wool before it leaves the farm gate.

Wool Characteristics

When compared to other fibres the natural qualities and properties of wool give it a unique advantage. Durability, versatility and the value of spun wool is directly related to the characteristics inherent in the wool fibre.

Wool is:

Fire resistant, a fabric made entirely of wool is difficult to ignite, burns slowly, and has limited ability to sustain a flame
Durable - the interlocking protein molecules with wool fibres have the power to elongate, stretch and recover, creating an extremely robust fabric that will last for years.
Thermal - it can store water vapour up to 35 per cent of its own dry weight yet it remains dry to touch and speeds up the body's own cooling system
Static resistant - the retention of moisture within the fabric prevents a build-up of static electricity.
Easy to dye - the scales on the surface of the wool fibre tend to diffuse light giving less reflection and a softer colour and wool holds its colour well as the dye becomes part of the fibre
Comfortable - its elasticity means garments fit so well and yield to body movement, it absorbs moisture, allows your body to breathe, yet never feels damp and clammy
Versatile - wool fabric, knitwear and carpets are made from a wide range of wool types varying from superfine for suits and knitwear through to broad fibres that give carpets their strength and character

The most important characteristics of wool in determining its value are fibre diameter, yield, staple length, colour and staple strength.

Fibre diameter - the mean fibre diameter is the average diameter expressed in micrometres or commonly, microns. Mean fibre diameter is the single most important wool characteristic, accounting for about 75 to 80 per cent of the value of the top. The importance of diameter lies in the fineness of yarns, which may be spun. Most of the fibre diameter variability encountered in wool arises because of differences within single fleeces.

Staple length staple strength and position of break - these characteristics may be used to predict processing and product properties. Staple length (mm) is highly correlated with mean fibre length in the top (hauteur).

The effect of staple strength is to modify expected processing behaviour and top properties of wool of a given staple length. Wool with lower staple strength will have more fibre breakage in processing and produce a top with lower hauteur. Staple strength is calculated as the force required to break per unit staple thickness, expressed as newtons per kilotex or N/tex.

The position of the break indicates where fibres are more likely to break first. Only the weakest point is noted. There is a tendency for wools with tip or base breaks to produce higher fibre losses, and for wools with middle breaks to produce tops with slightly shorter hauteur.

Yield - is used to estimate the quantity of useable wool fibre present.

Vegetable matter - is costly to remove and it may lead to a downgraded product if it is not removed. The level of vegetable matter is expressed as percentage vegetable matter base (vmb%), which is the amount of clean, dry vegetable matter present as a per cent of the greasy wool sample.

Crimp - the cortical structure of the wool fibre is related to crimp in fibres. Wool fibres with little crimp do not bind as well as fibres with crimp and therefore are harder for processors to spin.

Colour - clean wool colour after scouring varies from near white through shades of cream to yellow and brown. Occasionally bacterial action will lead to unusual shades such as pink or green. It is difficult to predict scoured colour from greasy colour.

Source: Australian Wool Innovation

Further information

Australian Wool Exchange

Australian Wool Testing Authority