WOOL
“The Wonder Fiber”
Wool Processing- (Woolen & Worsted both)
Introduction:
Wool is a fiber, which for generations is being provided by the different Wool bearing animals, like; Alpaca, Camels, Goats, Guanco, Llamas, Musk Ox, Rabbit, Sheep, Vicunas & Yaks etc. being bred in different countries.
A very important Wool variable is luster. Some Wools are dull, some glow like Silk, and some shine like Mohair. Mohair is not a Wool but a, hair from Angora goats. The Wool on each sheep is different from one part of the body to another. Wools also differ among individual sheep of the same breed, between sexes, & from year to year depending upon variables such as age, health, & nutrition. Differences also occur depending upon the quality of care given to the fleece prior to shearing, as well as afterwards during the cleaning & processing of the Wool.
“Virgin Wool" is the Wool which has not been spun or woven previously; it comes directly from the fleece of a live sheep.
"Fell" or "Pulled" Wool, is the fiber off a dead animal.
"Lamb's Wool" is Wool from sheep up to seven months old & is the first shearing.
The structure of Wool:
Wool is a protein fiber (Keratin) & this is the key to understanding the properties of Wool. Proteins are helicoidal makro molecules. In a Wool fiber, three of these proteins are wrapped around each other, thus retaining the cork screw like structure of the protein & forming the 'proto fibril'. Eleven proto fibrils form a 'micro fibril' & a large number of micro fibrils form a macro fibril, like a single thread in a rope the macro fibril is part of the cortex, which in itself is divided in two halves: the Para-cortex & the Ortho-cortex. Each of these halves has slightly different qualities, that give Wool fiber the characteristic "Crimp" or small curls. Finally, the enclosure of the fiber is an outer layer of tiny overlapping scales, 400- 800 per cm.
Ø Mechanical properties:
The helicoidal structure of the fiber & all its parts result in a resilient & elastic behavior.
Arrangement of Para- & Ortho-cortex
Woolen & Worsted- The Difference:
Woolen & Worsted are two major classifications for Wool yarns & fabrics.
The Woolen System
Woolen fabrics are characterized as being fuzzy, thick & bulky. They are made from fibers that are 1”- 3” in length that have been carded only (Worsted yarns are carded & combed). After the carding process the Woolen "Sliver" is drawn & twisted by machine into rope like strands called "Roving" & wound onto reels for spinning. Woolen yarns are fluffy, relatively loosely twisted, & are used in weaving fabrics such as Tweeds, Blanket cloth & Meltons. Woolen fabrics & yarns are traditionally made into bulky garments such as Coats, heavy Jackets & Sweaters.
· The Worsted System- Combing & Drawing
Wool of English long haired sheep is combed out until the strands lie parallel. Worsted yarn is spun from that Wool. It yields a more orderly yarn. The physical appearance of Worsted system fabric (mixed or pure) is harder & smoother, as compared to the fabric of Woolen system. Under a microscope, Worsted yarn looks more like rope than soft Woolen yarns. The soft yarns have loose ends that fly about and give them fuzzy edges. (See Picture)
That rough surface causes fibers to grasp one another. Wool made from non-worsted yarn can be felted, washed in hot water until the fibers cling to one another, regardless of the weave. The reason Wool shrinks so badly in hot water is that its fibers ratchet up along one another. They clump & then won't let go.
Worsted yarns are spun from 3” & longer fibers that have been carded, combed & drawn. Combing machines further straighten the Wool sliver making the individual fibers lie parallel. The combing process also eliminates "noils" or shorter fibers which grow mostly on the belly of the sheep. (Noils are used in the production of less expensive Woolen fabrics & for the manufacturing of felt, a non-woven fabric).
The drawing process takes the Worsted sliver, doubles it over onto itself & draws it out again to a thinner, more uniform diameter to ensure that all Wool fibers are parallel. Worsted yarns are twisted tighter & thinner in the spinning process & are manufactured into light weight fabrics such as Gabardine & Crepe.
Ø Properties of Wool:
Most of the fiber from domestic sheep has two qualities that distinguish it from hair or fur. It has scales which overlap like shingles on a roof & it is crimped. In some fleeces the Wool fibers have more than 20 bends per inch. The surface of Wool fibers consists of an outer layer of overlapping scales, called cuticles. Water droplets run off this layer easily, which is how sheep stay dry.
· Warmth & moisture retention
Due to its heterogeneous structure, the Wool fiber is very porous & reacts to changes in humidity. Wool, can absorb up to 30% of, its own weight in moisture, depending on the relative humidity. This is a very good value, compared to man made fibers with only 2-3% of moisture absorption. When boiled, the fibers kink & enmesh, forming a lofty, water repellent, breathable fabric. It is a good insulator & uniquely combines the three useful properties of water repellence, moisture absorption & breathability. The spring like form of the fibrils helps the fibers to cling together. Even loosely twisted yarns are strong & this, together with the fiber's elasticity, allows the manufacture of open structured yarns & fabrics that trap & retain heat insulating air. The result is a lightweight fabric with superior heat insulation, even in a cold & damp environment.
The surface layer of Wool contains small micro pores which enable the fiber to let air through it. The pores are so small that water droplets can not pass through the fiber's surface, but evaporated or molecular water (sweat) can pass through the surface pores. Therefore, Wool is some what water-repellent.
Wool is a protein fiber.
Wool is Bio Degradable.
Wool can be recycled.
Wool is highly absorbent & releases moisture slowly. It can absorb up to 30% of, it’s weight in moisture, without feeling wet & transports it to the outer surface of a fabric, where it evaporates into the atmosphere. This action keeps the human body cool.
Wool is a good Insulator. It doesn’t readily conduct heat. Wool is warm, because its fibers are non-conductors of heat. In a Woolen garment, crimp of the fibers keeps them apart from each other. Crimp permits them to enmesh still air. Still air is one of the best insulators found in nature. The trapped air keeps the body at an, even temperatures i.e. warm in winter & cool in summer. (See Picture)
Wool is Breathable.
Wool is Resilient.
Wool is an amazing fiber. It is extremely flexible & elastic, able to be bent back on itself over 25,000 times without breaking; compare this with Cotton, which breaks at 3,000 bends. It can be stretched up to 30% of its length when dry (double that when wet) & still snap back to its original shape. This makes for a very durable, tear resistant fabric that won’t wrinkle when made into a garment.
Wool, due to its molecular structure & the resiliency of its crimp, Wool fabrics are highly crease resistant.
Its tensile strength is one fourth greater, than that of Cotton.
Wool is, a protein compound of complex chemical composition, it is soluble in hot Caustic Soda.
Wool garments retain shape & can shed creases easily.
Wool is Anti Static.
Wool doesn’t generate Static charge, which attracts dirt.
Wool doesn’t get dirty & cleans easily.
Wool is Easy Care.
Wool is Safe.
Every fiber of Wool contains moisture, making it naturally flame resistant. Although, it can catch fire, it usually only smolders, when the source of the flame is removed, Wool will self extinguish. It does not melt the way most synthetic fibers do, so Wool will not stick to the skin if burned.
Wool is a versatile fiber, which can be easily converted to Knitwear & shawls of different weight & texture, also Sportswear, Casuals & formals.
Ø Drawbacks of Wool:
Wool shrinks in water.
Wool fibers have got, serrations or scales (like Saw Tooth), along it’s length (See Picture).
During the fiber mixing process, the direction of the fibers go haywire.
When the Wool fiber becomes wet with water, these serrations get locked into each other. The surface scales of the Wool fiber are responsible for the unique felting and shrinking properties of Wool when wet. The edges of the scale catch against those of neighboring fiber aligned in the opposite direction which allows them to move in only one direction.
This causes the matting of Wool fibers & consequently, the shrinkage of the Woolen Garments.
Ø Quality of Wool:
The quality of Wool is determined by the following factors; Fiber fineness, Fiber length, scale structure, Color, Cleanliness & freedom from damage. For example Merino Wool is 3”- 5” in staple length & is a very fine. Wool from the sheep meant for meat has fibers that are coarser, of greater diameter & 1.5”- 6” long. Freedom from damage refers to the structure of Wool when it is removed from the sheep & implies that the Wool is clean, white, long, fine & free of environmental defects.
Both the scaling & the crimp make it possible to spin & felt the fleece. They help the individual fibers attach to each other so that they stay together. Because of the crimp, Wool fabrics have a greater bulk than other textiles & retain air, which causes the product to retain heat. Insulation also works both ways.
The amount of crimp corresponds to the fineness of the Wool fibers. A fine Wool like Merino may have up to a 100 crimps per inch, while the coarser Wools like Karakul may have as few as 1- 2 crimps per inch.
Hair, by contrast, has little scales & no crimp & little ability to bind into yarn. Hair part of the fleece is called Kemp. The ratio of Kemp to Wool varies from breed to breed & make some fleeces more desirable for spinning, felting or, carding.
Wool is generally a creamy white color, although some breeds of sheep produce natural colors such as black, brown (also called MOORIT) & grey.
Wool straight off a sheep contains a high level of grease ("Greasy Wool") which contains valuable Lanolin, which is used in the cosmetics. This Wool can be spun into yarn or knitted into water resistant mittens or sweaters. The grease is generally removed for processing by scouring with detergent & alkali.
After shearing, the Wool is separated into 5 main categories: fleece (majority part), pieces, bellies, crutchings & locks. The latter 4 are packaged & sold separately. The quality of fleece is determined by a technique known as Wool classing. A Wool classer groups Wools of similar grades together to maximize the returns. Wool right off the sheep that has not been combed or carded is considered to be in “Lock” form. Sometimes it is raw from the sheep, full of dirt, grease (Lanolin), vegetable matter, & other interesting things that sheep roll around in on the pastures & hillsides.
The Wool fiber varies from 15 (superfine Merino) to 30 or more microns for the coarser Wools. The finer diameters are generally more valuable.
Due to high concentrations of Carbon Dioxide, sheep Wool does not burn & therefore is also used as insulation.
Ø No Itch "Feels Just Like Silk" (Bio Polishing):
When Wool is perceived as itchy, the reason is that there are coarse fibers in the Wool, which does not yield to the skin, but prick right in. Coarse fibers in excess of 28 microns may itch. The Woolen fabric becomes silky & machine washable, because of the hydrogen peroxide & enzymes used in the two step bio polishing process. The bio polishing whitens & eliminates or smoothes the scales on the Wool fibers. The scales cause Wool fibers to felt. They, along with the "crimp" of the fiber, give Wool yarns much of their "Wooly" body. In many applications Wool would not be Wool without its tiny scales which, when magnified, look like the shingles on a roof.
When you say "felt" there are generally positive connotations with the word. When you say "shrink" there are generally negative connotations. But felting, which is possible because of the scales, is only controlled shrinking. The scales are one of Wool's features that make it both uniquely valuable &, at the same time, limit its application. Bio polishing creates new applications for Wool by removing the scales on Woolen fibers without destroying their other positive features.
The novel ARS (Agriculture Research Service- USA) process involves treating the Wool in 30º C bath of activated hydrogen peroxide for 30 min. That bleaching process is followed by a bath in the enzyme mixture for 40 minutes at 40º C. The bleaching time is shorter & the temperatures are lower than what, are the norm.
"High temperature dyeing is traditionally used with Wool because of the lipid (Wool grease) barrier to dye uptake". "Although Wool has resilient properties, those high temperatures weaken the fiber. Our process lets Wool be dyed at lower temperatures, preserving its strength."
The same lipid layer that makes Wool resistant to dye uptake would protect the scales against such an enzyme attack. But bleaching removes the lipid protection. "No damage is done to the underlying fiber structure, & the fabric's mechanical properties, are not changed, because the enzyme activity is limited to the outside layer, or cuticle". An additive is used in both the bleach pretreatment & the enzyme treatment to keep the enzymes out of the fiber's inner structure.
The ARS process for machine washable, itch free Wool, bio polishing is patented & must be licensed by the firm or individuals who use it. (www.sheepmagazine.com)