Fabric

Cotton

A natural cellulose fibre. Absorbent, soft, tolerant of hot water and detergent, slow to dry. It holds moisture rather than moving it, which is a virtue against skin and a nuisance in a heatwave. See cotton and modal.

Modal and lyocell

Regenerated cellulose made from wood pulp. Smoother and more drapey than cotton, notably stronger when wet than viscose, and generally more resistant to pilling. Comfortable next to skin and quicker to dry than cotton.

Silk

A protein fibre. Fine, smooth, thermally adaptive, and chemically fussy: alkaline detergent and enzymes attack it directly. See silk and satin.

Polyamide

Also sold as nylon. The workhorse of bra construction. Strong, fine, abrasion resistant, holds dye well and takes heat setting, which is how moulded cups keep their shape.

Polyester

Stronger against light, less absorbent than polyamide and less pleasant against skin in a fine knit. Common in linings, moulded foam and sleepwear.

Elastane, sold under several trade names, is a segmented polyurethane that can be stretched to several times its length and return. Almost every stretch garment in a drawer relies on it, usually at a few per cent of the total fibre content, sometimes up to a fifth in a power mesh.

It is also the component that fails. Heat degrades it, chlorine attacks it, and prolonged tension gradually reduces its recovery. Every rule about washing intimates cool, drying them flat and keeping them away from radiators exists to protect this one material. Elastane and stretch covers the mechanism and the consequences.

The fabric almost never wears out first. The elastic gives up, and the garment stops doing its job while still looking perfectly presentable.

Most intimates are knitted rather than woven, because a knitted loop structure stretches in a way a woven grid cannot. Within that there are meaningful families.

• Warp knits, including tricot and raschel, are stable, run resistant and used for cups, bands and most lace.
• Power mesh is a firm, open warp knit with a high elastane content, used wherever compression is wanted, from bra wings to shapewear.
• Moulded foam is a laminated sandwich, usually polyurethane foam between two knit faces, heat pressed into a fixed cup shape.
• Jersey and rib knits are weft knits, softer and more elastic in every direction, used for bralettes, briefs and sleepwear.
• Woven fabrics appear mainly in silk slips, where drape rather than stretch is the point.

A label such as 82 per cent polyamide, 18 per cent elastane describes a firm, supportive stretch fabric, probably a power mesh, almost certainly in a band or a shaping panel. A label reading 95 per cent cotton, 5 per cent elastane describes a soft everyday knit with just enough recovery to hold a leg edge. A label reading 100 per cent silk describes something with no recovery at all, which must be cut to fit because it will not stretch to it.

The percentage of elastane is the single most informative number on the label. Below about three per cent, the fabric is essentially stable with a little give. Between five and twelve, it is a comfortable stretch knit. Above fifteen, it is doing structural work and will be firm on the body.

The last material question in the section is structural rather than textile: whether there is a wire, and what replaces it if there is not. Wired and wireless covers what a wire actually contributes, what a well built wire free bra substitutes for it, and where each is the better tool.