What is Wool?

Wool is an animal fiber obtained from the fleece of sheep or lambs. Turkey's textile fiber labeling regulation (Annex 1, no. 1; “the Turkish regulation” below) and the EU's Regulation 1007/2011 (Annex I, no. 1) define wool in the same way: fiber from the fleece of sheep or lambs (Ovis aries), or a mixture of that fiber with the animal hairs in list no. 2. Wool is made of the protein keratin; it keeps you warm, takes up and releases moisture as vapor, and stretches, which is why it is used in sweaters, suits, coats and socks.

Why wool fiber behaves the way it does

According to Woolmark, the fiber is about 97% protein and 2–3% lipid, and its surface is covered with overlapping scales (the cuticle) like roof tiles. The cortex, which forms the body of the fiber, gets the natural crimp from two cell types growing at different speeds; the crimp lets the fiber stretch and return without breaking. A textbook says the fiber consists of cuticle, cortex and medulla, and that its length varies from 1.5 to 15 inches (about 4–38 cm) with the breed of sheep (INFLIBNET). Cotton Incorporated, for its part, counts animal hairs such as wool among the “long staple” fibers shorter than 10 inches (25.4 cm). So length depends on the source and the breed.

Properties

• Warmth and moisture: Pratt Institute describes wool as a fiber that insulates well yet breathes, moves moisture, resists odor and helps manage body heat and sweat. Woolmark writes that the fiber's internal structure absorbs water vapor while letting excess heat escape; a textbook says it can take up about 20% of its weight in water without feeling damp (INFLIBNET). Annex 9 of the Turkish regulation accepts moisture allowances of 18.25% for combed wool and 17.00% for carded wool when calculating fiber content; this is a commercial calculation value, not a measurement.
• Strength and burning: According to a textbook, wool fabrics are considered very durable, but the fiber itself is weak; recovery from deformation (resilience) is highest when dry and lowest when wet. Wool burns very slowly and extinguishes itself (INFLIBNET).
• Heat, light and chemicals: At 100 °C wool becomes stiff and starts to degrade at higher temperatures; long exposure to sunlight weakens the fiber, and strong alkalis damage it quickly (INFLIBNET). Woolmark also recommends a mild, neutral detergent for wool.
• Felting: According to Woolmark, heat and moisture lift the scales on the fiber surface, and mechanical action locks them into the scales of neighboring fibers; this felting is irreversible and shrinks the garment. A textbook also advises against agitating wool while it is washed (INFLIBNET). Wool that has been through a felt-resist (shrink-resist) treatment is called “superwash” in the trade (Woolmark). Woolmark says products approved for machine washing, with a washable care claim, can be washed many times without shrinking.
• Moths: Moths eat the keratin of wool as food, and moth-proofing treatments are applied mainly to woolen fabrics (INFLIBNET). FabricLink recommends fresh cedar blocks for storage.

Wool types and label terms

Article 8 of the Turkish regulation accepts “100%”, “pure” or “all” only for products made entirely of the same fiber; up to 2% of foreign fiber that is unavoidable in good manufacturing practice and not routinely added (5% in products that have been carded) does not prevent this. For wool, the 2015 regulation text was used as of October 11, 2026; ask a regulatory specialist what the current rule is in the market where you will sell.

Buying wool yarn and fabric

1. Write the fiber name and percentage. The label of a woolen product must contain the word “wool”; a breed name such as merino is given separately as extra information. Under article 17/2 of the Turkish regulation, other information is always shown separately from the fiber composition.
2. Ask for the fineness (micron) band. In Woolmark's bands, under 19.5 microns is for next-to-skin wear and fine knitwear, 19.5–22 for apparel and knitwear, 22–24 for outerwear, and above 24 for carpets and interiors.
3. Write the yarn count with the name of its system. In wool yarns Nm is common; in the English system the hank length depends on the fiber, and for worsted wool it is 560 yards (MEB, 2014; TRI 1014). To convert, use the yarn count converter and the yarn count conversion guide; for suppliers, see the Wool Yarn category.
4. Ask for weight in g/m². To calculate it from a sample, use the fabric GSM calculator.
5. Have dimensional change measured. Change after washing is measured by ISO 5077, with ISO 6330 procedures; for cutting allowance, use the fabric shrinkage calculator.

For fabrics woven from wool, such as gabardine, see the fabric types guide. You can find wool fiber suppliers in the Textile Fibers category and wool blanket makers in the Blankets category.

Care

Woolmark writes that wool naturally resists stains, odor and wrinkling, so it needs less washing. For machine-washable approved products, it recommends a gentle wool program at about 40 °C; for hand washing, lukewarm water at about 30 °C; and flat drying. FabricLink lists resting the garment for 24 hours between wearings, dry cleaning once a season and using steam when ironing. Always follow the product's care label.

Frequently asked questions

Does wool make you sweat?

A wool garment does not prevent sweating; sweating is how the body gets rid of heat. Pratt Institute describes wool as a fiber that insulates well yet breathes, moves moisture and helps manage sweat. Whether a wool fabric feels cool or warm also depends on weight and structure as well as the fiber; for example, in a study of cellulosic knitted fabrics, low weight, low thickness and an open structure increased water-vapor permeability (Suganthi et al., 2024). The measurable values are air permeability (EN ISO 9237) and water-vapor resistance (EN ISO 11092). More in breathable fabrics for summer.

Does wool shrink or felt?

When heat, moisture and mechanical action come together, wool felts and shrinks, and the change is irreversible (Woolmark). Do not machine wash wool that has not been through the felt-resist treatment (superwash); on Woolmark-approved machine-washable products this claim is on the label. Have dimensional change after washing measured by ISO 5077.

Is merino a different fiber?

No. Merino is wool from a sheep breed with fine fiber. In the EU the label must carry the word “wool”, and the breed name is shown separately as extra information (European Commission FAQ 3.1).

Are cashmere and mohair wool?

In the Turkish regulation list, wool is the fiber of sheep or lambs; the hair of the Kashmir goat, the Angora goat (mohair) and the Angora rabbit (angora) has separate names in no. 2 (Annex 1). These names can also be used together with the word “wool” or “hair”. US law, on the other hand, includes the hair of the Angora and Cashmere goat in its definition of “wool” (15 U.S.C. § 68); for exports, use the definition of the target market.

What is the difference between wool and acrylic?

Wool is an animal protein fiber; acrylic is synthetic and was developed to compete with wool (CottonWorks). The Turkish regulation (Annex 9) accepts a moisture allowance of 17.00–18.25% for wool and 2.00% for acrylic. See the acrylic entry for details.