What Is Rayon (Viscose)?

How is rayon (viscose) made?

Rayon is made by dissolving plant cellulose into a thick liquid, pushing that liquid through the fine holes of a spinneret and hardening it back into cellulose as fibre. Viscose, the predominant form of rayon, takes its name from that syrupy spinning solution.

1. Cellulose. Cornell Cooperative Extension names wood pulp as the raw material; the US Federal Trade Commission (FTC) names bamboo as another possible source.
2. Dissolving. According to CAMEO, the materials database of the Museum of Fine Arts, Boston, the cellulose is treated with sodium hydroxide and then carbon disulfide, forming an orange, viscous solution of cellulose xanthate. That solution is the “viscose”.
3. Spinning. Cornell describes the solution being forced through spinnerets and hardened into filament.
4. Filament or staple. EU law defines viscose as made by the viscose process “for filament and discontinuous fibre”, so it can be a continuous filament or a cut, staple fibre.

The FTC puts it plainly: “there’s no trace of the original plant in the finished rayon product.”

A short history

CAMEO records that Charles Cross and Edward Bevan discovered the viscose process in England in 1892, and that several companies were making viscose rayon soon after the turn of the 20th century. Cornell says rayon became commercially available in the United States in 1910 and was widely known as “artificial silk”; the same sheet says the industry adopted the name “rayon” in the 1920s.

The rayon family

EU law names each regenerated cellulose fibre by its process. US rules are broader: rayon covers regenerated cellulose in general, with “lyocell” allowed for one type.

Acetate is not in this family. Both US and EU rules define it as a cellulose acetate fibre, a chemically modified cellulose rather than a regenerated one.

What are the properties of rayon?

Rayon is absorbent, dyes easily and costs relatively little, but it wrinkles easily and is weaker when wet, according to the University of Georgia Extension. It does not melt, though it may scorch.

• Wet strength. CAMEO gives a tenacity (breaking strength) of 2.0–2.6 g/denier dry for viscose rayon and 1.0–1.5 g/denier wet, roughly half. Cornell calls the wet strength of regular viscose “very low”.
• Shrinkage and stretch. Cornell says regular viscose can shrink as much as 10 per cent in ordinary laundering and can stretch out of shape if pulled while wet. Finishes have been developed to reduce shrinking, stretching and wrinkling, according to the University of Georgia.
• Moisture. CAMEO lists a moisture regain of 11–16.6 per cent: the weight of water the fibre holds from the air, as a share of its dry weight.
• Weak points. The University of Georgia says rayon is damaged by strong acids, mildew and perspiration.

Cornell calls rayon “the great imitator”, used in dressy cloths such as velvet and taffeta, and in blends, often with polyester, that imitate cotton, wool or linen. CAMEO lists “artificial silk” and “wood silk” among its synonyms, a reminder of the fibre rayon first copied: silk.

How is rayon graded or measured?

Rayon has no consumer grading scale: US and EU labelling rules set its fibre names, not grades. What matters is its type, whether it is filament or staple, and its wet performance.

The University of Georgia rates high-wet-modulus (HWM) rayon, the type EU law calls modal, at up to 50 per cent stronger than conventional rayon. CAMEO reports strength as tenacity in grams per denier.

How does rayon appear on a clothing label?

In the US a label may say “rayon” or “viscose”; in the EU it must say “viscose”, or modal, lyocell or cupro if the fibre is one of those.

Under US rules

• The FTC accepts the ISO 2076 fibre names. It notes that ISO “uses the name viscose for the predominant form of rayon” and says either name may be used.
• Rayon made by the solvent route may be labelled “lyocell” (16 CFR 303.7(d)).
• Fibres are listed by generic name and percentage by weight, in descending order. A fibre under 5 per cent is labelled “other fiber” unless it has a clearly established functional significance at that amount (16 CFR 303.3(a)). Wool is a further exception: the FTC says wool must be named with its percentage even below 5 per cent.
• Rayon made from bamboo should be labelled as such, for example “rayon made from bamboo”. Only fabric made from mechanically processed bamboo fibre can be called simply “bamboo”, according to the FTC.
• The label must also give the country of origin and the name or registered identification number (RN) of the manufacturer or of a company that markets or handles the product.

Under EU rules

• Only fibre names listed in Annex I of Regulation (EU) No 1007/2011 may be used, and each name is reserved for fibres matching its description (Article 5). Viscose is entry No 25. “Bamboo” is not an Annex I name, so a bamboo-derived viscose is labelled viscose.
• A “100%” or “pure” viscose label may still contain up to 2 per cent extraneous fibres, or 5 per cent for carded products, if that amount is technically unavoidable and not added routinely (Article 7(2)).
• Blends list every fibre by name and percentage by weight, in descending order (Article 9(1)).

How do you tell good rayon from poor rayon?

Good rayon is the right type for the job and finished against its weaknesses; poor rayon wrinkles, shrinks or sags.

1. Read the fibre name. “Modal” or “HWM” rayon signals a stronger, more wash-stable fibre than plain viscose. Cornell says HWM rayon can be machine laundered and performs much like cotton.
2. Read the care label. Cornell recommends dry cleaning for regular rayon. A “dry clean” instruction on a simple viscose shirt is a warning that it may shrink or distort in the wash.
3. Crush a corner. Squeeze a fold of fabric in your fist for a few seconds. Rayon wrinkles easily unless it has been finished against creasing, so deep creases that stay suggest an untreated or plain viscose cloth.
4. Check vintage underarms. Perspiration damages rayon, which is why the University of Georgia advises dress shields. Look for weakened or discoloured fabric at the armholes, and for mildew.
5. Know the look-alike. Acetate melts at low heat and is destroyed by acetone, the solvent in many nail polish removers; rayon does not melt but may scorch.

Red flags: a label that says only “bamboo” on a soft, silky fabric (under FTC guidance, rayon made from bamboo should be labelled as rayon); claims that bamboo rayon keeps the plant’s qualities; and fibre names missing or given without percentages.

How do you care for rayon?

Follow the care label and handle rayon gently while it is wet, when it is weakest; the University of Georgia notes that some rayon should be dry cleaned.

• If the label allows washing, use a short machine cycle, as the University of Georgia advises.
• Do not pull or wring wet rayon; Cornell warns that regular viscose stretches out of shape under tension when wet.
• Hang the garment to dry while still damp before putting it away, to avoid mildew.
• Press with a medium-hot iron. HWM rayon needs a lower temperature than conventional rayon.
• Avoid chlorine bleach unless the care label allows it: it can yellow or weaken some resin-treated rayon. The University of Georgia calls dry oxygen bleach safe.
• Remove oil and grease stains before washing.

Is rayon sustainable?

Rayon starts from a renewable raw material, but its conventional manufacture relies on hazardous chemicals, so “made from plants” does not make it sustainable on its own. Cornell describes wood pulp as an available and renewable source of cellulose.

The FTC states that rayon “typically is made using environmentally toxic chemicals in a process that emits hazardous pollutants into the air”. It adds that bamboo’s fast growth and low pesticide needs are “not the whole story” once the plant has been turned into rayon. A garment’s footprint depends on how the fibre was made, not on the word viscose or bamboo on the label.