Producing Wool

For thousands of years sheep have been among the most efficient of all the domestic animals. Unlike cattle and swine, they thrive in the most extreme conditions of climate and habitat. Sheep graze easily on noxious weeds in the highest reaches of mountain vegetation where neither cattle nor elk nor deer choose to feed; thus they convert to protein for human use a whole variety of natural resources that would otherwise be wasted.

These conversions are, of course, wool - the perfect fiber for uncounted varieties of fabric, and lamb - the most tender and succulent of meats. Shear a sheep and spin its wool into yarn for a sweater or a skirt. Before you know it, the sheep has grown a new fleece and the cycle starts all over again. Wool is a renewable resource. (Back to top)

Shearing & Grading

The first step in processing wool takes place on the farm or ranch with shearing… usually in the springtime just before lambing. A skillful shearer, using fast electric hand clippers similar to enlarged barber’s shears, can shear a sheep in about 5 minutes. He uses long, smooth strokes close to the skin in order to preserve the length of the fiber and hence the value of the fleece.

The shearer usually peels the fleece off in one piece. Then a worker rolls and ties it and stuffs it into a long bag with 19 or 39 other fleeces which together weigh from 200 to 400 pounds. He also marks the bag to identify its source (owner) before it goes to the warehouse.

Next come the buyers. They are the final judges of the value of the wool. Many times they take core samples of the bags of wool in order to measure fiber length, diameter, amounts of dirt, plastic, and vegetable matter. These factors can also be determined by experienced graders who make their judgements by visual inspection. The buyers bid on "the lot" based on the grade and/or the core samples of the wool.

Fine and medium-fine wools of longer staple lengths (more than three inches) usually go to make light-weight worsted suit and dress fabrics. Coarser and shorter fibers, under three inches long, usually go into bulky sweater and carpet yarns. (Back to top)

Washing and Scouring

The next step in the process is washing (scouring) the wool to remove grease (unrefined lanolin), vegetable matter and other impurities which gather in the wool from the range, feedlot, or shearing floor. A set of rakes moves the fleeces through a series of scouring tubs of soap and water. Impurities can weigh from 30 to 70 percent of raw (unscoured) fleece. The first wash waters are warm-up to 140 degrees F - and the rinses are cold. Then squeeze rollers and a hot-air drying chamber bring the moisture content to the right level for the next step in processing.

The grease in wool is a wonder of its own… lanolin. It is separated from the wash water (oil and water don’t mix), purified, and used in creams, soaps, cosmetics, and other products. (Back to top)

Blending and Dyeing

Clean wools from several different batches or lots are often blended-mixed mechanically-at this stage. Blending unifies the slightly-different basic colors of raw wool, and also helps to standardize staple length and diameter for uniform quality.

Each wool fiber absorbs dyes so deeply that dyeing at any processing stage is equally effective and durable. Wool dyed immediately after it is scoured (washed) and blended is stock-dyed. Spin it into yarn first and then it’s yarn-dyed. Weave it into a piece of fabric and then it is piece-dyed. To weave a patterned fabric, use either stock-dyed or yarn-dyed threads. Plain-colored fabrics are usually piece-dyed. And woolen fabrics can, of course, also be screen or roller printed in myriad colors and patterns. (Back to top)

Carding

The carding process passes the clean and dry wool through a system of wire rollers to straighten the fibers and remove any remaining vegetable matter. The rollers vary in diameter and turn at different speeds in order to form a thin web of aligned fibers. Smooth steel fingers then divide the web and roll the strands over onto one another to create narrow continuous ropes of fibers called "slivers".

If the batch of wool is of coarser fiber and shorter staple length (three inches or less), the machinery gently twists the slivers into ropelike strands called "roving", and winds the roving into balls ready for spinning into woolen yarns.

If the batch is of finer fiber and longer staple length (longer than three inches), the slivers usually go to the combing and drawings steps which prepare them for spinning into worsted yarn. (Back to top)

Spinning

Roving for both woolen and worsted yarns goes through the spinning process for yarn formation, making it suitable for weaving or knitting. After spools of roving are in place on the spinning frame, the ends of the roving are drawn through small rollers to extend the wool fibers still further. Then the spinning machines twist and retwist the roving into yarns of a wide variety of qualities including strength, firmness, size and ply.

(Back to top)

Weaving or Knitting

Weaving produces cloth by interlacing two sets of yarn at right angles. Yarns running lengthwise in the loom are the "warp", while yarns running crosswise form the filling or "weft". As each warp yarn passes through the loom, it is raised and lowered by a wire eyelet through which it is threaded. As yarns are raised and lowered by cycles of the loom, a weft yarn is carried by a shuttle, (rapier or air jet) through the opening created by the warp yarns. This sequence, repeated endlessly, forms woven fabrics of almost infinite variety.

Knitting machines are just as versatile. Their mechanical needles are just as accurate and many times faster than hand knitting. Knitted fabrics are produced by interlocking rows of yarns and loops. As new loops are formed, they are drawn through those previously shaped. This inter-looping and the continued formation of new loops produces knit fabric. A circular knitting machine produces mainly jersey and a variety of double knits. Flat knitting machines produce yard goods such as tricot and raschel knits. (Back to top)

Quality Control, Fulling and Finishing

Quality control inspection is a part of the final step in fabric manufacturing. A thorough examination of the cloth identifies imperfections such as broken threads, variations in color and other undesired effects. These are removed and the area is rewoven by hand if necessary.

Fulling: Once the fabric passes inspection, it undergoes a controlled shrinkage process call fulling or milling. Moisture, heat and friction are applied causing the fabric to shrink a controlled amount in both length and width. This tightens the weave and improves the hand (texture) of the fabric.

Finishing: Woolens are often brushed to raise the ends of the wool fibers above the surface of the cloth in a soft, fluffy nap. Naps range from the lightly brushed surfaces of a flannel to the deep-pile effect of fleecy coatings. Deep naps are produced by passing the fabric over cylinders covered with fine metal wires and small hooks. These hooks pull fiber ends to the surface and create the nap.

Worsteds go through less radical changes in finishing, although the characteristic crisp, firm appearance of worsted fabric is sometimes enhanced by special treatments. Clear finishing is shearing or singeing process which gives the fabric a smooth surface and a crisp feel. Unfinished worsted are lightly napped to give them a woolen-like surface producing a fabric with the softness of a woolen and the firmness of a worsted.

The decating finishing process is another shrinking process which gives the fabric stability. It is done by winding the fabric under tension on a perforated cylinder through which steam is passed.

Crabbing: sets the cloth and yarn twist by rotating the fabric over cylinders through hot, then cold water baths. The cloth is held firmly and tightly to prevent shrinking.

Sponging: is a preshrinking process achieved by dampening the fabric with a sponge, then rolling it in moist muslin. It is applied to wool fabric before cutting to prevent possible contractions of the fabric in the finished garment caused by stresses created in manufacturing. "London Shrinking" is a popular sponging treatment which prevents shrinkage during manufacturing. (Back to top)

Chemical Finishes

Several chemical finishes may be applied to wool, depending on their end use. Products labeled SUPERWASH , a trademark owned by The Wool Bureau, Inc. are 100% wool that can be machine-washed (using ordinary laundry detergent) and machine-dried. The process that qualifies SUPERWASH certification is a mild chemical treatment applied to the fiber to form a permanent microscopic film of resin which spreads evenly over the fiber surface, coating the scales of the wool fiber. The finish reduces friction and fiber entanglement and eliminates felting shrinkage that usually occurs if wool garments are machine-washed and dried. Wool can also be treated chemically to make it highly resistant to moths, stains, moisture and fire.

The finishing process is the final step in wool processing which takes the wool from the sheep’s back to woven or knitted fabric. (Back to top)