Fibres, yarns and fabric construction
Fibre classification and properties
Natural fibres are vegetable (cotton, linen), animal (wool, silk) or mineral. Manufactured fibres are either regenerated from cellulose (viscose, lyocell, acetate) or fully synthetic (polyester, nylon, acrylic, elastane). Link fibre to behaviour: cotton is absorbent and strong wet but creases; linen is cool and very strong but creases sharply; wool insulates, absorbs moisture vapour and felts; silk is lustrous and strong but degrades in sunlight; polyester is strong, quick-drying and thermoplastic but has low absorbency; elastane gives high stretch with poor recovery if overheated.
Yarn structure
Staple fibres are spun; filament yarns are continuous. Twist direction is S or Z, and twist level changes handle: high twist gives a lean, strong yarn, low twist a soft one. Two or more yarns plied together reduce snarling. Linear density is given in tex (grams per 1,000 m), so a higher tex is coarser. Blends combine properties - polyester/cotton gives strength and absorbency.
Fabric construction
Woven fabrics have lengthwise warp (straighter, stronger, often finer) and crosswise weft. Plain weave interlocks most and is firm; twill has a diagonal and drapes well; satin has floats giving lustre and snagging. Knitted fabrics are loops: weft single jersey stretches mainly crosswise and curls at edges; rib stretches widthways and recovers. Nonwovens are bonded webs with no grain. Selvedge, grainline and the 45° bias govern how a pattern behaves.
Worked example: why denim jeans are twill - a 3/1 twill puts more warp yarns on the face, so indigo shows while the undyed weft gives the pale inside; the diagonal floats resist abrasion, and the firm weave controls stretch.
Traps: calling satin a fibre; swapping warp and weft; assuming all knits stretch equally both ways; ignoring the bias when laying out.