Fabric
Cotton and modal
The two fibres that end up directly against skin most often, for reasons that are physical rather than sentimental.
Cotton is a cellulose fibre with a hollow, twisted structure that absorbs a considerable proportion of its own weight in water. Modal and lyocell are regenerated cellulose: wood pulp dissolved and extruded as a smooth, round filament. All three are hydrophilic, meaning they take moisture into the fibre itself rather than leaving it on the surface. That single property explains most of what they do well.
Absorbency, wicking and breathability
Three words that get used interchangeably and mean different things. Absorbency is how much moisture a fibre can take into itself. Wicking is how quickly moisture is moved along and spread out, which is a function of the fabric structure as much as the fibre. Breathability is the rate at which water vapour passes through a fabric, which depends mostly on how open the knit is.
Cotton is highly absorbent and poor at wicking: it takes moisture in and holds it, which is comfortable in small quantities and unpleasant once saturated, because wet cotton stays wet and loses its softness. Modal absorbs comparably and dries faster, because the smooth filament has less internal structure to hold water. Polyester absorbs almost nothing and wicks well, which is why it dominates sportswear and is a poor choice for a gusset.
| Fibre | Moisture uptake | Drying speed | Typical use next to skin |
|---|---|---|---|
| Cotton | High | Slow | Gussets, everyday briefs, jersey camisoles |
| Modal | High | Moderate | Soft briefs, bralettes, sleepwear |
| Lyocell | High | Moderate | Sleepwear, soft cup linings |
| Polyamide | Low | Fast | Cup fabric, bands, linings |
| Polyester | Very low | Fast | Moulded foam, outer layers, sportswear |
Why the gusset is cotton
Almost every brief, including those made entirely of lace or synthetic mesh, has a cotton or cotton blend panel at the gusset. The reason is that the vulval area is warm and produces moisture continuously, and a fibre that takes moisture into itself keeps the surface against skin drier than one that leaves it sitting there. A cotton gusset is also easier to wash properly at a temperature that actually cleans it.
Whether the gusset is genuinely against skin is worth checking, since some briefs line the gusset on the outside only. Turn the garment inside out and look at which face the cotton panel is on. General daily routines for the area, including why fragrance free washing is the usual advice, are set out in a plain guide published by inWonderstate, and the same principles are summarised on everyday intimate comfort.
Breathability comes from the openness of the knit. Absorbency comes from the fibre. A dense cotton jersey can be less breathable than an open polyamide mesh.
Modal, lyocell and viscose
All three are regenerated cellulose and often get lumped together, which is unfair to two of them. Standard viscose is weak when wet and can lose a substantial share of its strength, which is why viscose garments distort in the wash. Modal is produced with a modified process that gives much better wet strength. Lyocell uses a different solvent process again, is stronger still, and has the smallest environmental footprint of the three in terms of solvent recovery.
For intimates, modal and lyocell are worth the preference: they are smoother than cotton against skin, drape better, resist pilling better and survive washing without distorting. Their weakness is that they are usually blended with only a little elastane, so a modal brief relies on cut rather than stretch to stay in place.
Washing and shrinkage
- Cotton knits shrink on first wash unless pre shrunk. Wash at 40 degrees rather than 60 to limit it, unless a gusset genuinely needs a hotter wash.
- Modal and lyocell are dimensionally more stable but dislike high heat in a dryer, which makes them harsh.
- None of these fibres needs fabric softener. Softener coats the fibre and reduces absorbency, which defeats the purpose of choosing them.
- Any elastane in the blend sets the real temperature ceiling. A 95 per cent cotton, 5 per cent elastane brief should be treated as an elastane garment, not a cotton one.
- Dry flat or on a line. Repeated hot tumble drying is what turns a soft cotton brief hard and shapeless.
Elastane and stretch covers why that last point matters more than any of the others.