What Is Viscose?

Viscose is a semi-synthetic fabric commonly used as a substitute for silk. It was developed in the late 19th century after a silkworm blight made natural silk – which was already very expensive – almost completely unaffordable. It became hugely popular because of the way it draped on the body.

Viscose is not quite synthetic, as it's made from cellulose (as all early plastics were), but it is not quite natural either, due to the extensive chemical transformations it is put through.

The first artificial silk was Chardonnett silk, made with celluloid and invented by Hilaire de Chardonnet. This fabric had just one problem: it was highly flammable. In "Plastic: The Making of a Synthetic Century," Stephen Fenichell describes how, in about 1891, “a fashionable young lady’s ball gown, accidentally touched by her escort’s cigar, disappeared in a puff of smoke on the ballroom floor." It was taken off the market.

Then, in 1892, viscose was invented by Charles Cross and Edward Bevan. They treated cellulose with caustic soda and carbon bisulfite, which yielded a thick honey-like thick liquid with high viscosity that they imaginatively named viscose. They turned it into a solid plastic to compete with the flammable celluloid, but didn't have much luck making a fiber out of it.

In 1899, Charles Topham bought the rights to make fiber from viscose, but was also having trouble making it strong enough. Inspired by a spinning bicycle wheel, he developed the “Topham Box,” which spun at 3,000 RPM and flung out perfect viscose fibers. Within months, he was cranking out 12,000 pounds a day, and he soon licensed it to manufacturers around the world.

Traditionally, cellulose can be derived from many different sources, from wood fiber to bamboo to seaweed. It is first broken down with caustic soda, also known as lye or sodium hydroxide. Then, it is treated with carbon disulfide and diluted with more caustic soda, which results in the viscous syrup that was the source of its name. This syrup is then pumped through tiny holes of the spinning shower into a bath of diluted sulfuric acid, sodium sulfate, and zinc sulfate, where it congeals into fibers of almost pure cellulose.

There is not much difference between the various sources of cellulose. Between 2007 and 2010, green websites (including Treehugger), extolled the virtues of bamboo fabrics, claiming it was "green" because bamboo is such a fast-growing plant. However, in 2010, the Federal Trade Commission put an end to this, writing:

The soft textiles you see labeled ‘bamboo’ don’t contain any part of the bamboo plant. They are made from bamboo that has been processed into rayon using toxic chemicals. When bamboo is processed into rayon, no trace of the original plant is left.

In 2007, the New York Times investigated Lululemon's claims about the virtues of adding seaweed to its fabric. The lab tests could not find a trace of seaweed in the material. In the end, cellulose is cellulose, and it all ends up as indistinguishable viscose.

The main practical difference between viscose and fully synthetic materials like polyester is that viscose is water-absorbing and breathable, so it can keep you feeling cooler on hot days.

There's no difference between viscose and rayon. In its early, no one liked the name viscose, and calling it artificial silk made it sound, well, artificial. So, in 1926, the US-based National Retail Dry Goods Council held a nationwide contest to come up with a better name. The losers included Glista and Klis (silk spelled backwards – get it?). The winner was rayon, a play on the French word rayonner, meaning “to shine through” – a reference to the fabric's silklike luster.

In 1930, Saks Fifth Avenue advertised the material: “Rayon! it’s like the time we live in! Gay, colorful, luminous. It’s so pliable to work with and so luxurious in appearance.”

Viscose is completely biodegradable. Unlike polyester, it is not made from petrochemicals, and it will not add to the plastic load in the ocean.

The biggest issue with the making of viscose is carbon disulfide. It's extremely toxic, and inhaling small doses can cause irritability and headaches. Higher doses and more prolonged exposure, experienced by workers in viscose plants, can cause bigger problems, including "nightmares, sleep disturbance, irritability, and memory disturbance" as well as "peripheral neuropathy, parkinsonism, and retinopathy," according to Tracy J. Eicher in Clinical Neurotoxicology.

In 1972, an American company developed a process that eliminated the carbon disulfide, directly dissolving the cellulose in the less toxic and more environmentally benign N-methylmorpholine N-oxide, (NMMO) in what is called the Lyocell process. The company went bust before bringing the product to market, but the process was picked up in the 1980s by Courtaulds Fibres, who called it Tencel.

The end result of the Lyocell process is nearly identical to viscose – in the end, it's all cellulose. However, because it is made without carbon disulfide, it is a greener alternative.