Shearing usually occurs in spring or early summer. (Sheep are sheared many times throughout their lives to remain comfortable and healthy.)
An expert can shear a sheep in about five minutes removing the fleece in one piece. An average sheep fleece weighs about 8.5 pounds. It’s enough wool for a suit.
The Merino sheep is the ancestor for all the present sheep breeds that are the producers of the highest quality wool.
A fine wool like Merino may have up to a hundred crimps per inch where the coarser wools like karakul may have as few as one to two crimps per inch.
The quality of the breed was improved by choosing only the strongest animals with the finest wool as breeders.
At the end of the 18th century, Merino sheep were transported to England France, and Germany as breeding-stock.
Even though Merino sheep never succeeded in England due to climate, the British were able to breed their own tough crossbred-sheep, which produced medium fine wool and meat.
This helped the British to take a leading role in the world’s wool industry.
Properties Of Wool
Wool fibres have a very unique chemical and physical properties. The wool fibre is composed of layers: the outermost cells form scale-like plates (cuticula).
Cuticula is formed of three layers which contain proteins and saccharides. A layer of wax, which protects the fibre from the weather, covers the surface of cuticula.
Only vaporized moisture is able to penetrate this wax layer. The separate layers of cuticula are held together by a protein glue.
The inner layer of the wool fibre is divided into two different halves: paracortex and ortocortex. The growth of wool fibre is asymmetric, as the hardening (keratinization) of paracortex begins earlier than the hardening of ortocortex.
This asymmetry results in a crimp that is typical of wool. The composition of ortocortex is more loose than that of the paracortex, which causes the greater ability of ortocortex to absorb water; as the wool gets wet, the crimp increases Cortex contains fibril-structured keratin protein which has the large molecular size and amorphous keratin that has smaller molecular size.
Microfibrils are organized to form macro fibril structures, which are held together by amorphous protein.
The chemical structure of wool reveals that it is almost solely made of keratin proteins. The cortex consists of about a hundred proteins differing from each other in their molecular structure.
Molecules are attached to each other by hydrogen bonds forming long molecule strings. Research has found in wool 22 different amino acids that differ from each other by their structure and molecular behavior.
Some of them absorb water(hydrophilous), some repel water, some contain sulfur, some are acid, some are alkali.
Amino acid molecules can form strings in countless different ways and wool fibre is reaction prone when it comes into contact with water or air.
This polymorphism of wool results in an ability to absorb large quantities of water. The proneness of wool to react with substances also causes its ability to produce warmth, for in the formation of new chemical bonds warmth is released.
Types/varieties of Wool Fibre
There are four main types of wool fibre.
This is the highest, finest and best wool obtained from sheep.
Merino wool, which is the best quality of wool, is always combed and manipulated into the high-grade fabric.
This is of good quality but not always satisfactory for combing purposes. Most carding wool is of varying staple length and used for woolens.
This is a term used to designate staple length when grading wool and attributed to fine wools below 1.25 inches in staple length and of 64s and over.
Any wool not classed in the above grades and it has the lowest quality amongst the four types. This class is used for carpet, floor-coverings, and such products as low-quality boys’ apparel and ski cloth.
General Properties Of Wool Fibre
- Wool consists largely of a protein substance called keratin which comprises of more than 20 different types of amino acids.
- The natural color of wool varies, depending on the breed of the sheep. Most wools, however, are yellowish- white or ivory in color after scouring. Some fibres may be grey, black, tan or brown.
- The best quality wools have only a slight luster. Fine and medium wool tends to have more luster than very coarse fibres.
- Wool is not a very strong fibre and its strength decreases by 10% to 15% when wet. When compared with other fibres, wool is weak and this weakness restricts the types of yarns and fabrics that can be used satisfactorily.
- It has excellent elasticity and extensibility and can be considered as the most extensible of natural fibres It has excellent resiliency: as the fibre will regain its shape easily after crushing or creasing, wool fabrics are crease resistant.
- Woolen garments are bad conductors of heat and therefore they keep the body warm. They contain a large volume of still air.
- It is a very absorbent fibre and will hold 29% of its weight in water without feeling wet, however, it does not dry quickly. Because of this affinity to moisture, wool can be dyed well with a variety of dyes.
- It does not soil easily but it absorbs odors.
- Wool felts, i.e., it tends to shrink when wet and under friction.
- Wool can be dry-cleaned and pressed easily but laundering is difficult unless the fibre or fabric has been treated to be washable.
- It is easily damaged by chlorine bleaches, by mildew bacteria, and alkalis.
- It is attacked by moth and can turn yellow upon exposure to sunlight.
- Wool burns slowly; it is considered non-flammable as the fibre will generally stop burning once the source of the flame is removed.
Applications of Wool Fibre
Wool is widely used because of its outstanding properties- being naturally crease-resistant, flexible, elastic, absorbent, warm & comfortable.