What is viscose, and why does it go limp and shrink when wet?

Viscose is everywhere in high-street clothing because it drapes like silk and costs like cotton. It also accounts for a large share of ruined garments, because it looks like a natural fibre, feels like a natural fibre and behaves like neither. The behaviour is entirely explained by how it is made.

Step by step

1. Understand what it is.Cellulose from wood pulp is dissolved in caustic soda and carbon disulphide, then extruded through a spinneret into an acid bath where it re-forms as filament. The cellulose is chemically the same as cotton, but its internal structure is far less ordered.
2. Understand why disorder matters.Cotton fibre has highly crystalline, aligned cellulose chains. Viscose has a much more amorphous structure, so water penetrates it easily, swells it and pushes the chains apart. That is the source of every characteristic on this list.
3. Expect it to be weak when wet.Viscose loses roughly half of its tensile strength wet. A soaked viscose dress lifted by the shoulders can distort or tear under its own weight, and rubbing wet viscose against itself abrades it.
4. Expect shrinkage.Viscose shrinks more than cotton and can continue to shrink over several washes. A viscose garment that is exactly right when you buy it will often not be after washing.
5. Expect water spots.A single drop of water on some viscose fabrics leaves a permanent ring, because the fibre swells locally and the finish moves. This is one of the honest reasons for a dry clean only label.
6. Wash it, if you are going to, correctly.Hand wash in cool water with a gentle detergent, move it as little as possible, never wring it, lift it supporting its whole area, press the water out in a towel and dry it flat away from heat and sun.
7. Iron it damp, on low.Viscose creases persistently and does not release creases with steam the way cotton does. Iron on a low setting while still slightly damp, from the reverse, with a pressing cloth on anything dark.
8. Take dry clean only seriously here.On an unlined, unstructured viscose top the label is often precautionary. On a lined dress, a pleated skirt or anything with interfacing, the shrinkage differential between the viscose and the lining will ruin the garment in one wash.

Tips

• Rayon, viscose rayon, art silk and bemberg or cupro are all in the same family. Modal and lyocell are made from the same raw material by better processes and behave much better.
• Viscose burns like paper with a smell of burning leaves, which is a fast way to tell it from polyester, which melts and smells chemical.
• A viscose garment that has shrunk can sometimes be eased back by damp blocking — pin it out to shape on a towel and let it dry — but rarely all the way.
• Viscose blended with polyester behaves far better wet than pure viscose, because the polyester carries the load while the viscose is weak.

Common mistakes

• Hanging a wet viscose dress on a hanger to dry — It is at its weakest wet and the whole weight of the water hangs from the shoulders. It stretches permanently, and sometimes tears.
• Machine washing a lined viscose garment — The viscose and the lining shrink by different amounts, and the result is a puckered garment that cannot be corrected.
• Spot cleaning a viscose top with water — The water mark can be more visible than the stain was. Treat the whole panel or take it to a cleaner.

Questions people ask