Fibre guide
Viscose is not afraid of water. It is afraid of force while wet.
A viscose garment can wash perfectly and still come out stretched because lifting, wringing or tumbling loaded the fibre at the moment it was weakest.
Last updated 1 September 2026
Rayon and viscose are the same family
Rayon is the broad US name for regenerated cellulose fibre; viscose is the predominant name used by ISO and in Europe. The US Federal Trade Commission explicitly allows either term. A label saying “bamboo” usually does not mean mechanically processed bamboo fibre: the FTC says a fabric made by dissolving bamboo cellulose must be labelled rayon or viscose made from bamboo.
The raw material is cellulose, as it is in cotton. The difference is structure. Cotton grows as an organised natural fibre. Viscose is dissolved and regenerated, leaving more of its cellulose accessible to water. Water interrupts bonds between the chains, the fibre swells, and standard viscose loses a large part of its tensile strength.
| Label name | Wet behaviour | Practical reading |
|---|---|---|
| Viscose / rayon | Can retain only about half its dry strength | Minimise load, rubbing and distortion while wet |
| Modal | Higher wet modulus than standard viscose | Usually more stable, but the sewn-in label still decides |
| Lyocell | Much higher wet strength | Often washable; surface fibrillation can still occur under abrasion |
The useful rule: do not treat “viscose”, “modal” and “lyocell” as interchangeable marketing words. They are related cellulosic fibres, but their wet strength differs enough to change how cautious you need to be.
Why a dress grows longer in the wash
Wet viscose is both weaker and more extensible. A heavy, saturated skirt hanging from a narrow waistband loads the fabric lengthwise. A drum repeatedly lifts and drops it. Wringing concentrates the same load into a small twisted area. None of those forces has to tear the fabric to change its shape.
That is why “hand wash” does not mean scrub it by hand. Support the whole garment in the water, move it gently, and press between rinses instead of wringing. When lifting it out, gather it in both hands or support it on a towel rather than pulling it up by one shoulder.
The safe method
- Read both labels. Fibre content tells you the vulnerability; the care label accounts for dye, finish, lining and construction.
- Use cool water and a short gentle process. A mesh bag reduces snagging in a machine. Avoid an overloaded drum, where garments rub instead of moving freely.
- Use a measured dose of detergent. More product creates a harder rinse, not extra safety.
- Press, do not twist. Roll the garment in a towel if it is still heavy with water.
- Reshape before drying. Lay knits flat. A stable woven blouse can dry on a broad hanger if its label permits, but do not hang a heavy saturated dress.
Ironing and steam
Iron on the reverse at the lowest temperature that works, ideally while the fabric is slightly damp or through a pressing cloth. Do not pull a softened wet edge straight under the iron: pressing can set the distorted shape. Steam can relax creases, but it also supplies the moisture that makes standard viscose easier to stretch.
If it has already stretched
There is no reliable chemical “un-stretch” treatment. Rewetting according to the care label, supporting the whole garment and laying it to the original measurements can correct mild distortion because the fabric has not necessarily been permanently damaged. Broken yarns, puckered seams and a lining that now hangs at a different length are professional repair problems.
The short version
- Viscose and rayon are naming variants for the same broad fibre family.
- Standard viscose can lose roughly half its strength when wet; modal and lyocell are more stable.
- The main danger is force while saturated: tumbling, wringing, lifting from one point and hanging heavy.
- Support it, press water out, reshape, and dry without a concentrated load.