Natural and man-made fibres

Natural and man-made

Natural fibres are grown. Man-made fibres are regenerated from dissolved wood cellulose or synthesised from oil-based polymers, and made as continuous filament or cut staple. Polyester is now over half of world fibre output; cotton is about a fifth.

Cotton in depth

Upland cotton (Gossypium hirsutum) is most of world production. Extra-long staple (ELS) cotton (Gossypium barbadense: Pima, Giza) has a staple of 1 3/8 inch (about 35 mm) or more and goes into the finest yarns.

• Staple length: the mean length of the longer half of the fibres; upland usually 25–30 mm. Longer fibre spins finer, stronger, less hairy yarn.
• Length uniformity: mean length as a percentage of staple length; 80–82 is average, 83–85 high. Low uniformity means more short fibre and thick places.
• Strength: bundle breaking force in g/tex; 29–30 is strong, 31 and above very strong.
• Micronaire: airflow through a fixed mass of fibre, reading fineness and maturity together; in the US loan schedule 3.7–4.2 earns a premium, 3.4 and below or 5.0 and above a discount.
• Maturity: how far the fibre wall has thickened. Immature fibre breaks, forms neps and dyes paler: white specks in dark shades.
• Colour and trash: reflectance (Rd) and yellowness (+b) set the colour grade, such as 31 (Middling, white); trash is the surface share of leaf and bark.

Each bale’s sample is conditioned at about 21 °C and 65% relative humidity and measured on an HVI (High Volume Instrument); a classer adds the leaf grade.

Organic, Better Cotton, recycled

• Organic cotton is grown without synthetic pesticides or fertilisers, from non-GM seed, on certified organic farms; it is around 1% of world cotton. OCS or GOTS tracks it through the chain; GOTS also covers environmental and social conditions in processing.
• Better Cotton comes from licensed farms that follow its principles on crop protection, water, soil and decent work. Most is sold under mass balance: purchases are matched by licensed output, but the product need not contain that cotton. Physical models (segregation, controlled blending) keep it separate and traceable to its country of origin.
• Recycled cotton is cutting waste or used textiles shredded back into fibre. Being shorter, it is usually blended with virgin cotton or polyester and spun open-end; RCS or GRS certification verifies the content.

Blends and why they exist

A blend combines fibres for properties none has alone, or to reach a price. It is written by weight, main fibre first: 60/40 cotton-polyester.

• Cotton-polyester (CVC when cotton is over half): stronger, faster-drying, shrinks and creases less, costs less; less absorbent, pills more, and needs two dye classes.
• Cotton-elastane, often 95/5 in jersey: stretch and shape recovery for fitted garments.
• Cotton-linen: linen’s cool, dry hand and slubby look with cotton’s softness.
• Cotton-viscose and cotton-polyester-viscose: a softer hand, more drape, and a heathered look in T-shirts.