Fiber Processing
Organic Wool Processing restricts chemical inputs and requires the separation of organic and non-organic fibers throughout processing stages.
Shearing & Grading
The first step in processing wool, hearing, takes place on the farm or ranch, most often in spring, just before lambing. A skillful shearer, using electric hand clippers, can shear a sheep in about 5 minutes, using long, smooth strokes close to the skin that preserve the length of the fiber and maximize the value of the fleece.
The shearer typically peels the fleece off in one piece. A co-worker rolls, ties, and stuffs it into a long bag with 19 to 39. The bag, weighing between 200 to 400 pounds, is marked to identify its source (owner) before it goes to the warehouse.
Next come the buyers, the judges of the value of the wool. Repeatedly they take core samples of the bags to measure fiber length and diameter, but also to assess residual amounts of dirt, plastic, and vegetable matter. Experienced graders can make their assessments by visual inspection. The buyers then bid on "the lot".
Fine and medium-fine wools of longer staple lengths (more than three inches) are desirable for light-weight worsted suit and dress fabrics. Coarser and shorter fibers, under three inches long, are used mostly for bulky sweater and carpet yarns.
Washing and Scouring
The next step is washing, or "scouring," the wool to remove grease (unrefined lanolin), vegetable matter and other impurities remaining 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 account for 30 to 70 percent of raw (unscoured) fleece weight. The first wash waters are warmed to 140 degrees F, followed by cold rinses. The wool passes squeeze rollers and a hot-air drying chamber reduce the moisture content to the desired level.
The grease in wool is a wonder of its own... lanolin. It is separated from the wash water (oil and water don't mix), and purified for eventual use in a wide variety of creams, soaps, and cosmetics.
Blending and Dyeing
Clean wools from different batches or lots are often blended-mixed mechanically-at this stage. Blending minimizes the basic color variables of raw wool and standardizes staple length and diameter, resulting in uniform quality.
Wool fiber is so absorbent that dyeing at any stage of processing is equally effective. Wool dyed immediately after it is scoured (washed) and blended is "stock-dyed." Spun into yarn and it's" yarn-dyed." Woven into fabric and it is "piece-dyed."
Patterned fabric is woven with either stock-dyed or yarn-dyed threads. Plain-colored fabrics are usually piece-dyed. And woolen fabrics can, of course, be screen- or roller-printed in myriad colors and patterns.
Carding
The carding process passes the cleaned and dry wool through wire rollers to straighten fibers and remove remaining vegetable matter. The rollers vary in diameter and turn at different speeds in order to create 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 them into balls ready for spinning.
If the batch is of finer fiber and longer staple length (longer than three inches), the slivers usually go to combing and drawings steps that prepare them to be spun into worsted yarn.
Spinning
Before it is suitable for weaving or knitting, roving for both woolen and worsted yarns goes through the spinning process. Spools of roving are placed on the spinning frame, their ends drawn through small rollers to extend the wool fibers still further. Finally, the spinning machines twist and retwist the roving into yarns of various strength, firmness, size, and ply.
Weaving and 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 (commonly by a rapier or air jet) through the opening created by the warp yarns. This sequence, after many repetitions, forms woven fabrics of infinite variety.
Knitted fabrics are produced by interlocking rows and loops of yarns. 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. Knitting machines are as versatile as looms. Their mechanical needles are more accurate and many times faster than hand knitting. 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.
Quality Control, Fulling, and Finishing
Quality control inspection is the final step in fabric manufacturing. A thorough examination of the cloth identifies broken threads, color variations, or imperfections. These are removed, and the area rewoven, by hand if necessary.
Fulling: Once inspected, the fabric undergoes a controlled shrinkage called "fulling" or "milling." Moisture, heat, and friction are applied to shrink the fabric a controlled amount. This tightens the weave and improves the hand (texture).
Finishing: Woolens are often brushed to raise the ends of the wool fibers in a soft, fluffy nap above the surface of the cloth. Naps range from the lightly brushed surfaces of a flannel to the deep-pile 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 to create the nap.
Worsteds go through less radical finishing, although their characteristic crisp, firm appearance can be enhanced by special treatments. "Clear finishing" is a shearing or singeing process that produces a smooth surface and a crisp feel. Unfinished worsted are lightly napped to give them a woolen-like surface, resulting in a fabric that combines the softness of a woolen and the firmness of a worsted.
Decating 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 in which the fabric is dampened with a sponge, then rolled in moist muslin. Sponging is applied before cutting to prevent contraction of the finished garment caused by manufacturing stresses. "London Shrinking" is a popular sponging treatment which prevents shrinkage during manufacturing.
For more information about wool processing, please see the American Sheep Industry Association's Wool Information - please note that Superwash is not permitted in organic standards. |
