What Is Wool?

Wool is a natural protein fiber harvested primarily from domestic sheep (Ovis aries) and, in smaller quantities, from goats (cashmere, mohair), rabbits (angora), and camelids (alpaca, vicuna). The fiber's principal structural component is keratin, a family of fibrous proteins whose alpha-helical chain configuration gives wool its distinctive combination of crimp, elasticity, moisture management, and thermal insulation. These physical and chemical properties have made wool one of the most widely used textile fibers throughout recorded history, and they continue to make it relevant in both traditional textile manufacturing and emerging technical textile applications where its functional characteristics are difficult to replicate synthetically.

Each wool fiber is a hierarchical biological structure. The outermost layer, the cuticle, consists of overlapping scale-like cells that facilitate the mechanical interlocking of adjacent fibers during spinning and felting. Beneath the cuticle lies the cortex, a bundle of cortical cells filled with macrofibrils built from intermediate filaments embedded in a matrix of non-crystalline proteins. The molecular-scale spring of the alpha-helical keratin chains stores elastic energy when the fiber is stretched, allowing wool to recover from deformation, a property that gives fabrics made from it their wrinkle resistance and dimensional stability during wear.

Fiber Properties and Processing

Wool fiber is characterized by its fineness (measured in micrometers of fiber diameter), staple length, crimp frequency, and clean yield after scouring. Merino wool, the premium fine-apparel grade, typically measures 15 to 24 micrometers in diameter; coarser carpet wool may exceed 40 micrometers. Raw wool, called greasy wool, contains lanolin, vegetable matter, and soil that must be removed by aqueous scouring before further processing. Dyeing of scoured wool exploits the fiber's reactive protein surface, which accepts a wide range of acid dyes, metal-complex dyes, and reactive dyes at high fastness levels. ScienceDirect's coverage of the chemical and physical properties of wool situates these fiber characteristics within the broader materials science of textile substrates.

Yarn and Fabric Production

Wool is converted to yarn through carding or combing, drawing, and spinning. Woolen yarns, produced by carding without full alignment of fibers, have a lofty, irregular structure suited to insulating fabrics like blankets and tweeds. Worsted yarns, produced by combing to align fibers parallel before spinning, are smooth, strong, and used in tailored apparel, suiting, and fine knits. Yarn twist, count, and ply determine the mechanical properties of the intermediate product and, in turn, those of woven or knitted fabrics constructed from it. Wet finishing processes, including milling, raising, and pressing, further modify the surface texture and dimensional stability of finished cloth. The Tandfonline review of keratin regeneration from wool waste examines how dissolved keratin can be reprocessed into new fiber forms, a development relevant to circular economy approaches in textile manufacturing.

Wool in Technical and Smart Textiles

Beyond traditional apparel, wool is used as a substrate for functional and electronic textiles. Its hygroscopic nature allows it to absorb up to 30 percent of its dry weight in moisture vapor without feeling wet, making it useful in sportswear and protective clothing where moisture management is important. Wool's natural flame resistance, attributed to its high nitrogen and moisture content, suits it for aircraft seating, carpet in public buildings, and firefighter undergarments. Researchers have explored wool-nylon hybrid substrates coated with conductive polymers such as PEDOT:PSS for use in wearable sensors, exploiting the fiber's flexibility and skin comfort. The PMC review of smart e-textiles components covers the integration of sensing and actuation elements into fabric substrates including natural fiber materials.

Applications

Wool has applications in a wide range of fields, including:

• Apparel and fashion: fine merino knitwear, worsted suiting, and outdoor performance garments exploiting thermal regulation and moisture transport
• Technical textiles: flame-retardant aircraft seating covers, carpet in public buildings, and protective clothing for industrial workers
• Interior textiles: upholstered furniture, area rugs, and acoustic wall panels benefiting from wool's sound-absorbing properties
• Wearable electronics: conductive yarn substrates for textile-integrated sensors measuring body temperature, motion, and electrophysiological signals
• Insulation: building insulation batts and acoustic panels made from low-grade or recycled wool fiber