Wool is nothing but the high polymer of amino acid. Repeating unit of which are joined together an acid-amide (-CO-NH-) type of bond called peptide linkage. Wool protein is called keratin. Wool is a fibrous protein derived from the specialized skin cells and is taken from animals in the Caprinae family, principally sheep, but the hair of certain species of other mammals including: goats, llamas, and rabbits may also be called wool. Wool has several qualities that distinguish it from hair or fur: it is crimped, it has a different texture or handle, it is elastic, and it grows in staples.
Classification of wool
On the basis of length and Diameter
Short & Fine: American Merino-1.5 to 2 inch, Rambouillet 2.5 to 3.5 inch, Australian Merino 3 to 5 inch. Medium & Medium: England down 2 to 4 inches, Correlate 3 to 7 inches, Long and Coarse:Romney sheep 5 to 6 inch, Blackface Highland 6 to 8 inch,Cotswold 10 to 14 inch.
On the basis of Length they are further classified as Combing wool: It includes the fibers that are combed in preparation of worsted yarns. Its staple length ranges from 2 to 4 inch. Clothing wool: Fibers are les than 2 inch in length and are used in the construction of woolen yearns. Its length ranges from 0.5 to 2 inch.
On the basis of Sheep
Class-I Wool/Marino wool: Merino sheep of Spain produces the best quality wool which is strong, fine, elastic and has good working properties. It has the greatest amount of crimp of all wool fibers and has a maximum numbers of scales to give maximum warmth and spinning qualities.
Class-II Wool: It is obtained from the sheep from England, Scotland, Ireland and Wales. Fiber length ranges from 2 to 8 inch, has a large number of scales per inch and has good crimp. the fibers are strong, fine, elastic, and have good working properties.
Class-III Wool: This class of sheep if found in United Kingdom. The fiber length ranges from 4 to 8 inch, coarser and has fewer scales and less crimp than Merino wool and class II wool. They are smoother and have more luster. They are less elastic and resilient. They are nevertheless of good enough quality to be used for clothing.
Class-IV Wool: This class is actually a group of Mongrel sheep sometimes referred to as half-breeds. The fibers are 1 to 16 inch long, coarser and hair like, have relatively few scales and little crimp and therefore, smoother and more lustrous. It has least elasticity and strength and used mainly for carpets, rugs and inexpensive low-grade clothing.
The Merino Wool The source of merino wool is merino sheep, a bread that originated centuries ago in Spain. (the word “merino” has Spanish roots.) Merino sheep were introduced to Australia in 1794, and they flourished in he island nation’s temperate interior. Today the majority of merino sheep are raised in New Zealand (at high elevations), Australia, South Africa and South America where to climates and the vegetation consumed by sheep contribute to the exceptional quality of merino wool. It is estimated that 1square inch of skin on a merino sheep produces roughly 4 times the number of fibers than other breeds.
Wool may be shared from the living animals or pulled from hide after the animal has been slaughtered for its meat. The sheared wool is called fleece or clip wool. Wool which is taken from the slaughtered animal hide is called pulled wool and is frequently of inferior/lower quality. The processing of wool fibers can be put under the headings of: 1) shearing, 2) grading, 3) spinning preparation, and 4) spinning.
Sheep are sheared by skillful shearers who do the job by using electric hand clippers similar to enlarged barber’s shares. Smooth strokes close to the skin of the animals are used for obtaining lengthy fibers so that the fleece remains valuable. Grading: After shearing the wool is separated into main categories: fleece 9which makes up the vast bulk), broken, pieces, and locks. The latter three are pressed into wool packs and sold separately. Grading is done for establishing the quality of raw fiber in respect of fiber length, diameter (microns), colour, amount of dirt, and other impurities.
These factors are determined either by the experienced Graders or by the prospective buyers themselves who take the samples for the purpose. Graders can do the job simply through visual inspection. Fibre diameter is the single most important wool characteristic determining quality and price. Spinning Preparation60% (on the basis of weight) of the raw wool fiber is composed of impurities and only 40% of it is usable wool fiber. the impurities present in wool are of three types: natural; acquired; and applied impurities.
Natural impurities are the glandular secretions that adhere to the fleece. Suint and wool grease, together known as yolk, are such two major components. Suint is the dried perspiration of sheep that is water soluble. Wool grease is water insoluble and requires special scouring for its removal. The acquired impurities include soil, dust, dirt, straw, vegetable and fecal matter. Applied impurities are due to the treatments given to the animal against insects, pests etc. and due to the markings made on them with tar or paints for their identification. The fibre preparation includes a) garmeting & carbonizing, b) washing and scouring, c) drying, d) oiling, and e) blending.
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