THE WOOL

Origins of wool | The main sheep breeds | Sheep breeding | Morfology | Proprieties | Phases of processing | Ennobling

 

The origins of wool

It is thought that already during the Stone Age, some 10,000 years ago, the inhabitants of Asia Minor used sheep not only for food, but also for their wool, which they used to make clothes and shelters. In China and in Egypt felts made from wool were already common, before tools such as shears were invented and used. During the Iron Age, with the introduction of cutting utensils, wool was sheared from the sheep, instead of it being strapped. Soon after man learned to spin and weave the wool which became an essential element of the life of the community. Between 3000 and 1000 AC the Persians, Greeks and the Romans contributed to the introduction of the rearing and breeding of sheep in all of Europe, and at the same time improving the breeds. In particular, with the expansion of the Roman Empire the herds of sheep began to be imported in a systematic manner in the regions of current Spain, the North Africa and the British Isles, and the major part of the population, particularly in Northern Europe, began to use wool for is clothes. Moreover the wool made it possible, thanks to its excellent properties of insulating, to face the rigid and cold winters. Through the conquest of Spain by the Saracens and the presence of Normans, a people of Scandinavian origins, in Southern Italy and Eastern Mediterranean, the commerce and spread of wool experienced a strong expansion. The XIV century saw the breeding of Merino sheep in Spain, a breed of sheep that produced the finest wool available, and the resulting flourishing trade of wool contributed to financing the voyages of Christopher Columbus, who introduced sheep into Cuba and Santo Domingo, which later introduced and spread by Cortez in current Mexico and the Southern and Western United States. Both Spain and England subsequently introduced laws, which forbade the export of sheep and raw wool. King Henry the VIII of England, despite his disloyal and unfair treatment of the monasteries shepherds reached the peak of success and importance for his kingdom (1509-1547) largely thanks to the development of the wool trade. The attempts by the English to discourage the growing wool trade and industry in North America, making it a punishable by cutting off the offender's right hand, did not stop the sector growing until the outbreak of the American War of Independence (1775-1783). The policy of keeping herds, practiced by both George Washington and Thomas Jefferson, and the new inventions for the working of wool, such as the "Spinning Jenny", water looms and machines for combing yarns all contributed to its subsequent flourishing development. The end of the XVIII century saw the breeding of sheep in Australia which currently holds some 160 million heads of sheep, equivalent to 14% of the world's total sheep reserves.

 

The main sheep breeds

The Merino sheep produces fine wool between 15 and 23 µm (micrometer = 1:1.000.000 of m). Morbid and short – the length varies between 50 and 120 mm – it very crimpy (curly), and comes mainly from Australia, South Africa and countries belonging to the former Soviet Union. Its main use is for fine clothes, both knitwear and fabric. The Cheviot sheep, instead, provides bulkier wool that measures over 30 µm, and is robust, smooth and slightly crimpy, that reaches a length of more than 150 mm. It is mainly produced in New Zealand and in Great Britain and mainly used for furnishing textiles combed yarns with a hard surface. The Crossbred sheep (a cross between a Merino and a Cheviot sheep) produces a medium-fine wool between 24 and 30 µm, of medium force, with few curls and a length that can vary between 120 mm and 150 mm. It is mainly bred in Argentina and in Uruguay and its wool used to produce combed yarns, destined for clothing that is heavy, hard-wearing and sportswear.


Sheep breeding and the production of wool and its classification

Globally, the main areas of breeding are Australia, countries of the former Soviet Union China, New Zealand, Argentina, Uruguay, South Africa, Great Britain and Pakistan. During the last one hundred years the world production of wool has roughly doubled, reaching a quantity of approximately 1,5 million tons of scoured (degreased -with the fat or grease removed from the wool which allows eliminating the lanolin and other residues, and reduces the weight of wool by approximately 40%) and corresponds to approximately 2.5 million tons of unscoured wool (without the grease being removed). Wool is classified, in addition to its fineness and quality, on the basis of the following types: • Sheared or virgin wool, which is obtained from live and healthy animals, with shearing that can be annual, half-yearly or 8 months. • Lambswool, which is derived from the first shearing of lambs 6 to 7 months old. The hairs of lambswool have sharp ends similar to the points of needles. • Cured or dead wool is obtained from dead animals and is normally used, due to its poor quality it is mixed with sheared wool. • Lye or Dead Wool is derived from slaughtered or already butchered sheep; • Waste Wool, of poor shoddy quality, is obtained from the scraps leftover from the manufacturing of clothes and garments or from used clothes.


Morphology of wool

Composed of protein molecules called keratin, wool is very suitable for human clothing. The chain of protein molecules form fibrils (very small fibres) that combine into fibrillar bundles, which form the mass of the spindle cells. This construction gives the wool fibre an extraordinary elasticity. Within the fibre two separate components or sub-fibres, that have different chemical constructions, wind in a spiral around each other in a bilateral structure. It is this bilateral structure that causes the fibre to be crimped (curly), as moisture and temperature have different effects on the two components, which swell to different extents, causing changes in the overall fibre shape. Consequently heat and the humidity of steam is used to create a series of links between the two fibres, which stabilizes when they cool. The ability of wool allows it to absorb moisture (it can absorb up to 30% of its own weight without giving the impression of being wet) and to be able release it slowly and gradually. However, in spite of the strong affinity for water wool is water repellent, because a very thin waxy layer covers it. The scales on the fibre surfaces are capable of hooking onto one another to cause felting under the influence of water, heat and mechanical action.



Proprieties of wool

Though offering good resistant the fibres of wool tend to wear out before other fibres used for clothing. Its elasticity however is exceptional and creases quickly disappear, especially if steam is used. It easily stretches when the fibres are wet or humid. To prevent this it is essential to dry clothes or garments flat and not hang them. There is however the problem of felting, caused by the directional friction effect of scales on the fibre surfaces when it is subjected to moisture, heat, and pressure. Wool fibres produce low electrostatic charges thanks to the humidity that is always present in the fibres which favours the electric “ discharge to earth“. Wool has very high heat absorption: trapping large quantities of air through the scales on its surface of the wool and the crimpy structure of its scales, which creates a type of thermal insulation from external elements. This factor is notably different in so-called cool wool where the crimping or curling of the fibres is much lesser which however drastically reduces its insulating powers. The fineness can vary importantly depending on the quality of wool; to distinguish the variety called “Super“ microns are used to measure its properties which must not be more than 18.5 µm: To define the Super 100’s cloths, this value must increase in scale up to 15 µm, the value necessary to make textiles in the Super 170’s. Finally, wool is not flammable, does not spread flames, does not fuse, and when it burns it does not stick to skin. The main phases of processing wool Grading where after shearing the wool is graded and sorted into four main categories (starting from the finest and then decreasing), the aim of which is to differentiate the wool according to its quality. The quality of wool is determined by the following factors, fibre diameter, crimp, yield and colour. The wool from the belly is normally heavily contaminated. Scouring, as already mentioned, is the process through which wool is delicately scoured or cleaned, so as to eliminate the grease (lanolin), dirt and burrs, with a consequent reduction in its weight. The average weight of the fleece of an Australian sheep is around 4 to 5 Kilos. Carbonizing removes, when necessary, vegetative impurities by immersion in dilute sulphuric acid. In the Carded wool system the raw wool is extracted from the compressed bales and deposited onto a beater, a drum with coarse pointed teeth. This operation, called beating, comes before the mixing and oiling which determines the preparation of the final lots of yarn as well as preparing the yarn for the subsequent processing. Picking is the phase during in which the wool fibres are opened up so as to be able to pass a constant quantity continuously for the carding, through which the fibres are opened and blended and also loosens dirt and vegetable matter thereby further eliminating impurities in the wool. The carding process forms the web, which is subsequently divided into small strips called rovings through the use of drums or belts rotating in an opposite direction. This generates the slivers, which, through spinning and on the basis of the fineness of the quality desired, are blended into skeins. In the Combed Wool system an initial selection of the fibres is made that consists in separating the wool into wool flakes and the elimination of rough impurities. It is then washed – this allows eliminating dirt and grease by using a bath of water and soda –, the fibres are dried using hot air and then sent for beating to open the fibres and further clean them. As in the carding system, the wool is then mixed, oiled, picked and carded. Stretching is done to straighten and untangle the fibres and make the previously created strips uniform as well as to mix and blend the different types of colours and fibres. Combing removes the short fibres and the subsequent straightening makes the fibres even more uniform and prepares them, after being compressed in the stretching tub, for the actual spinning of the yarn. The spinning is done in three phases, another stretching to improve once again the regularity of the fibres, the formation of slivers through a series of twisting spinning and then a final spinning, by which the wool is spun and twisted and stretched again depending on the quality and fineness required. The repetition of the twisting, stretching and combing allows producing wool yarns that are smooth, sleek and compact that we are used to.

 

Ennobling wool

Permanent fixing –done using chemical products, pressure and heat –, allows to permanently remove ironed creases. The process of decatizing subjects high-quality wool and woollen-blend fabrics to a treatment of steam under pressure, which produces a discreet sheen or glaze finish and provides a pleasant sensation when the fabric is handled. The fabric is enclosed between two layers of cloth and steamed and then rapidly cooled using cold air. An anti-pilling treatment allows washing wool without the risk of pilling. This is done by subjecting the wool to a chemical treatment, which substantially reduces its pilling characteristics. Treating wool with Mitin or Eulan is done to make it mothproof, while treatment with silicone makes the fibres waterproof. Fulling is a process used to eliminate oil and grease from the fibres of wool; after which, through agitation in water in controlled conditions, with the addition of fulling agents, the fibres are swollen again to make them grow and become longer. The addition of softeners also improves the pleasantness of the cloth to touch.