Processing wool transforms a greasy, dirt-laden fleece into clean fiber ready for spinning into yarn. The basic sequence involves five core steps: skirting, scouring (washing), removing vegetable matter, carding or combing, and spinning. Whether you’re working with a single fleece at home or thinking about how mills handle thousands of pounds, the stages follow the same logic.
Skirting the Fleece
Skirting is the first hands-on step after shearing. You spread the entire fleece out on a flat surface (a skirting table with a mesh top works best) and remove the unusable edges. The belly wool, leg wool, and any heavily soiled or matted sections around the tail get pulled away and discarded. These areas tend to be shorter, coarser, or too contaminated with manure and urine to be worth cleaning.
While skirting, you’re also picking out obvious debris: large pieces of straw, burrs, second cuts (short bits left by a second pass of the shears), and any wool with visible damage or discoloration. A well-skirted fleece saves enormous time during every step that follows. If you skip this or rush it, you’ll be fighting vegetable matter and low-quality fiber through the entire process.
Scouring: Washing Out the Grease
Raw wool is coated in lanolin, a waxy grease the sheep produces to protect its fleece from weather. A freshly shorn fleece can be 30 to 50 percent heavier than the clean fiber inside it, depending on the breed. Scouring removes this grease along with dirt, sweat salts, and anything else clinging to the fibers.
At home, scouring typically means a series of hot water baths with dish soap or a dedicated wool wash. You submerge the wool in water around 140°F (60°C), let it soak for 20 to 30 minutes, then gently lift it out and repeat with fresh hot water. Two to four baths usually does it. The critical rule: don’t agitate the wool. Wool fibers are covered in tiny overlapping scales, and when those scales are exposed to heat, moisture, and friction simultaneously, they lock together and felt. That’s irreversible. You want the hot soapy water to dissolve the grease while you leave the fiber alone.
Industrial scouring works on the same principle but at scale. Mills run fleece through a series of wash bowls with progressively cleaner water and mechanical rollers. The grease-laden wastewater is a significant environmental concern because of its high pollutant load. Treatment systems use a combination of anaerobic biological processing and chemical flocculation to separate the wool grease from the water, removing over 80 percent of the grease before the effluent can be safely discharged. The recovered lanolin itself is valuable, refined and sold for use in cosmetics and skin care products.
Removing Burrs and Vegetable Matter
If your fleece came from sheep that grazed near thistles, hay, or brush, you’ll find bits of plant material tangled deep in the fiber. Small amounts can be picked out by hand during skirting and carding. Larger quantities require a more aggressive approach.
At the industrial level, this is handled through carbonization. The wool is soaked in a dilute sulfuric acid solution (typically around 5 percent concentration), then squeezed to remove excess liquid and baked in an oven at roughly 250°F. The acid chars the cellulose-based plant matter into brittle carbon fragments without destroying the protein-based wool fiber. The carbonized debris crumbles away when the wool is subsequently passed through rollers or mechanical pickers, and the fiber is then washed or neutralized to remove residual acid. Higher acid concentrations or higher baking temperatures remove more vegetable matter but also risk weakening the wool, so the process requires careful balance.
For home processors, carbonization isn’t practical. Your best options are hand-picking during carding or choosing fleeces from breeds and farms where vegetable contamination is minimal.
Carding vs. Combing
Once the fiber is clean, it needs to be organized before spinning. This is where the path splits into two distinct methods, each producing a fundamentally different type of yarn.
Carding
Carding tangles the fibers together into a soft, fluffy mass. Think of it as teasing hair rather than smoothing it. You pull the clean wool between two paddle-shaped hand carders covered in fine wire teeth, which opens up clumps and mixes the fibers in random directions. The result is a rolag or batt: a light, airy preparation where short and long fibers are blended together with pockets of trapped air between them.
Yarn spun from carded fiber is called woolen yarn. It’s lofty, soft, and warm because all that trapped air acts as insulation. This is the yarn you want for knit sweaters, socks, gloves, and woven winter coats. It has a slightly fuzzy surface and more elasticity than its counterpart.
Combing
Combing does the opposite. It aligns all the long fibers parallel to each other and removes the short ones entirely. The result looks like smooth, sleek hair, with every fiber running in the same direction. The prepared fiber is called top or roving.
Yarn spun from combed fiber is called worsted yarn. Because the fibers lie close together with no air gaps, worsted yarn is smoother, stronger, harder, and cooler to the touch. Fabrics made from worsted yarn drape well and hold a crease, making them ideal for dress pants, suit jackets, and lightweight tailored garments.
The choice between carding and combing depends on what you plan to make and the staple length of your fleece. Short, fine fleeces work well carded. Long, uniform fleeces are better suited to combing.
Spinning Fiber Into Yarn
Spinning is where prepared fiber becomes yarn. The basic mechanics are simple: you draw out a thin strand of fiber and twist it. The twist locks the individual fibers against each other through friction, creating a continuous thread with surprising strength.
Hand spinners use either a drop spindle (a weighted stick that hangs and rotates freely) or a spinning wheel. A drop spindle is inexpensive and portable, making it a good starting point. A spinning wheel is faster and allows more control over the thickness and twist of the yarn. In either case, you draft the fiber with your hands, controlling how much feeds into the twist at a time, which determines the yarn’s thickness.
The direction of twist matters. Most singles (a single strand of spun yarn) are spun with a clockwise, or Z-twist. To make a stronger, more balanced yarn, you ply two or more singles together with a counterclockwise (S-twist) spin. Plying evens out inconsistencies and prevents the finished yarn from curling or biasing when knit or woven.
Dyeing at Different Stages
Color can be added at almost any point in the process, and the stage you choose affects the final result. Stock dyeing means dyeing the loose fiber before carding or combing. This gives the deepest, most even color penetration and allows you to blend dyed fibers of different colors during carding for heathered effects. Top dyeing applies color to combed fiber (the sliver or roving), which also produces even results. Yarn dyeing happens after spinning, and piece dyeing happens after the yarn has been woven or knit into fabric.
Wool is a protein fiber, chemically similar to human hair, and it accepts acid dyes readily. The dye is fixed using heat: you simmer the fiber in a dye bath with a mild acid (white vinegar or citric acid for home dyers) until the color exhausts from the water into the fiber. The process works because heat opens the fiber’s cuticle scales slightly, allowing dye molecules to penetrate, and cooling locks them in place. Rinsing afterward removes any unfixed dye.
Storing Processed Wool
Wool is naturally hygroscopic, meaning it absorbs and releases moisture from the surrounding air. Under standard conditions (around 65 percent relative humidity and 70°F), wool holds a measurable amount of water relative to its dry weight. This is normal and actually beneficial: it contributes to wool’s comfort against the skin and its resistance to static. But it also means storage conditions matter.
Keep processed wool in a breathable container, never in airtight plastic bags where trapped moisture can encourage mold. Cedar chests, cotton bags, or cardboard boxes in a dry room all work well. Moths are the other major threat. Clean wool with no residual lanolin or dirt is less attractive to moths than raw fleece, but lavender sachets, cedar blocks, or sealed storage during warm months provide additional protection.