Wool is shorn from sheep once or twice a year. Around 220,000 tonnes – about 5.4 kilograms per sheep – is harvested annually in New Zealand.
Fine, finer, finest
The finest Merino wool is the most valuable because it can be made into lightweight, soft fabrics for fashion clothing. When wool testing began in the 1980s, the average fibre diameter of New Zealand Merino wool was 20 to 21 microns. Once farmers identified their finest sheep, they could breed from them so over time the whole flock became finer. The average diameter is now about 19 microns, and the finest is as low as 12 microns – the finest wool in the world.
Wool properties and uses
All wool is classified before it is sold. Environmental, management and genetic factors all have a marked influence on its properties, including fibre diameter, length, tensile strength, yield (the proportion of clean washed wool from the original greasy state), colour and bulk. These all affect the use to which the wool can be put. For example, very fine, white Merino wool is suitable for making soft fabrics that can be dyed a wide range of colours and worn against the skin. Strong and off-coloured wool from a Drysdale would make a fabric too coarse to wear, which could only be dyed dark colours – so it is used for carpets and not apparel.
Strong or coarse wool is suitable for blankets, upholstery fabric, curtains and carpets. Short, discoloured wool can be used for insulation, or for absorbing industrial spills. Protein extracted from wool is used in cosmetics and medicine. Wool grease (lanolin), which is recovered from the wool scouring process, is a base in many cosmetic products.
Wool is tested to ensure that residual insecticide levels from dipping or spraying the sheep are below internationally acceptable minimum levels.
Shoddy, twaddle, tops and yarns
Shoddy is woollen cloth that is torn up, shredded and made up into new fabrics. Twaddle is the measure of the strength of a solution of sulfuric acid used to remove burrs from wool. Tops are wool that has been scoured and combed. Yarns are spun from tops, and are then ready to be woven or knitted.
Wool is largely processed outside New Zealand. About 80% is scoured in New Zealand to remove grease, dirt and other contamination. Nearly 70% is exported raw or scoured, to be spun and woven overseas. Of the 30% processed in New Zealand, just over half is made into carpets, rugs or other finished products locally. The rest goes through various stages of wool processing, including combing, spinning and being made into yarn.
Many advances have been made in New Zealand in developing processing techniques that enhance wool as a product. These include shrink-proofing, permanent creasing, flame and insect resistance, and extraction and purification of wool grease.