Making wool is a multi-step process that transforms raw sheep fleece into usable yarn or fabric. It starts with shearing the sheep and ends with spinning, plying, and sometimes dyeing the finished fiber. Each step along the way removes impurities, aligns the fibers, and builds strength into the final product. Here’s how the entire process works, whether you’re doing it by hand or trying to understand industrial production.
Shearing the Sheep
Wool production begins with shearing, typically done once a year in spring before warm weather arrives. The shearer positions the sheep on its rump and works through six basic body positions, using electric clippers to remove the fleece in one continuous piece. The goal is to keep both hands free: one holding the shears, the other pulling the skin taut so the blade cuts close without nicking the animal. Starting at the breast and belly, the shearer works methodically around the legs, neck, and back, repositioning the sheep between each section so its own body weight holds it steady against the shearer’s legs.
Sheep must be dry before shearing. Wet wool is difficult to cut cleanly and prone to mold during storage. Depending on the breed, the fleece can range from an inch and a half to six or eight inches long, with British breeds like Lincoln and Leicester producing some of the longest fibers.
How Much Usable Fiber a Fleece Produces
A raw fleece is far heavier than the clean wool you’ll actually use. Sheep produce natural grease (lanolin), sweat salts, and pick up dirt, sand, and plant matter throughout the year. Depending on the breed and living conditions, raw wool can contain anywhere from 15 to 80 percent non-fiber material. In practice, most fleeces shrink by 20 to 54 percent once fully cleaned. A 10-pound fleece from a greasier breed might yield only 5 pounds of usable fiber, while a cleaner fleece could retain closer to 8 pounds.
Scouring: Washing Out Grease and Dirt
The cleaning step is called scouring, and its success depends almost entirely on water temperature. Lanolin melts at 120°F, but as the water cools it can reharden and redeposit onto the fiber at around 110°F, leaving a sticky residue. Aiming for 130°F gives you a comfortable margin to dissolve the grease before it has a chance to resettle.
For small-scale processing, the fleece goes into mesh laundry bags and soaks in hot water with a degreasing detergent. Dish soap works, and many hand processors add a biodegradable cleaner to boost grease removal. The key rule is gentle handling: agitating wool in hot water causes the fibers to felt together permanently. You submerge the bags, let them soak, then lift them out and repeat with fresh hot water until the rinse runs clear. Two to three washes is typical.
Carding vs. Combing
Once the wool is clean and dry, the fibers need to be organized before spinning. There are two approaches, and they produce very different types of yarn.
Carding tangles the fibers together, mixing short and long strands into a soft, fluffy preparation. Think of it like teasing hair. The resulting yarn (called woolen yarn) traps air between the fibers, making it lofty, warm, and slightly fuzzy. This is the yarn you’d want for cozy sweaters, blankets, and insulating garments.
Combing does the opposite. It removes the short fibers entirely and aligns the long ones so they lie parallel, like neatly brushed hair. Yarn spun from combed fiber (called worsted yarn) is smoother, stronger, harder, and produces a fabric that feels cooler against the skin. Suit fabrics and dress pants are typically made from worsted yarn.
Hand carders look like wide brushes with fine wire teeth. You load wool onto one paddle, then brush the second paddle across it repeatedly until the fibers form a uniform sheet called a rolag. Combing uses metal-tined combs that are heated and worked through the fiber to pull out the long staples. Industrial carding machines accomplish the same thing at scale, processing hundreds or thousands of pounds of fiber per day.
Spinning Fiber Into Yarn
Spinning adds twist to the prepared fiber, and that twist is what turns a loose cloud of wool into a continuous, strong strand. Without twist, wool has no structural integrity. The more twist you add, the stronger and firmer the yarn becomes, though too much twist makes it wiry and stiff.
Twist direction matters. Most spinners produce what’s called a Z-twist for their initial single strand, meaning the fiber spirals in the same direction as the center stroke of the letter Z. The twist direction affects how the yarn behaves in knitting and crocheting. A left-handed crocheter, for instance, may find that Z-twist singles unravel during use, while S-twist singles (spiraling in the opposite direction) stay together. Matching your twist direction to your craft technique prevents the yarn from splitting or losing its structure as you work with it.
Hand spinners use either a drop spindle (a weighted stick that hangs freely and rotates) or a spinning wheel, which uses a foot pedal to drive the twist mechanically. Industrial ring spinning frames operate at 8,000 to 25,000 revolutions per minute, producing yarn at vastly higher speeds while maintaining precise tension control.
Plying for Strength and Balance
A single strand of spun wool tends to twist back on itself. Plying solves this by twisting two or more singles together in the opposite direction from their original spin. If the singles were spun with a Z-twist, they get plied with an S-twist. This creates a balanced yarn that won’t curl, snarl, or untwist during use.
Plying does more than just prevent twisting. It significantly increases the yarn’s tensile strength by binding the individual strands together, which in turn increases the cohesion between fibers within each strand. Plied yarn is also more uniform and more resistant to abrasion than a single of the same thickness. Two-ply is the most common, but three-ply and four-ply yarns are used for projects requiring extra durability, like socks or outerwear.
Dyeing Wool
Wool can be dyed at several stages: as raw fiber, as spun yarn, or as finished fabric. Natural (undyed) wool comes in white, cream, gray, brown, and black depending on the sheep breed, but most commercial wool is dyed to specification.
For natural dyes, the fiber first needs a mordant, a mineral compound that helps the dye bond chemically to the wool’s protein structure. The most popular mordant is alum (potassium aluminum sulfate), which has been used for centuries and produces bright, clear colors. Iron sulfate darkens and “saddens” colors, pulling them toward muted greens and grays. Copper sulfate shifts colors toward blue-green tones. These metallic salts have served as both mordants and color modifiers since at least the 3rd century in the Mediterranean.
Mordanting is done as a separate soak before dyeing. The fiber sits in a warm mordant bath, absorbs the mineral salts, and is then transferred to the dye pot. Without a mordant, most natural dyes wash out quickly. With one, the color becomes resistant to both washing and fading in sunlight.
Wool Grades and Quality
Wool quality is measured by the diameter of individual fibers, expressed in microns. Finer fibers feel softer against the skin and command higher prices. The USDA grading scale breaks wool into several categories:
- Ultra-fine: 17.69 microns or less. This is merino-grade wool used for next-to-skin garments and luxury textiles.
- Fine: 17.70 to 20.59 microns. Still soft enough for clothing, used in high-quality knitwear and suiting.
- Medium: 20.60 to 30.99 microns. Versatile wool used for blankets, upholstery, and general apparel.
- Coarse: 40.21 microns or more. Durable and resilient, best suited for rugs, carpets, and outerwear that doesn’t touch bare skin.
The breed of sheep determines where the wool falls on this scale. Merino sheep produce ultra-fine fiber, while breeds like Romney and Lincoln produce medium to coarse wool better suited for hard-wearing textiles.
From Yarn to Fabric
Once you have finished yarn, it becomes fabric through either knitting or weaving. Knitting interlocks loops of yarn to create a stretchy, flexible fabric. Weaving interlaces two sets of yarn (warp and weft) on a loom to produce a stable, structured cloth. Industrial looms operate at 200 to 800 picks per minute, with environmental conditions tightly controlled at 65 to 75°F and 55 to 65 percent relative humidity to prevent static and fiber breakage.
After weaving or knitting, wool fabric often goes through finishing steps like fulling (controlled shrinking that tightens the weave), pressing, and sometimes brushing to raise a soft nap on the surface. These final treatments give wool its characteristic drape, resilience, and texture.