Viscose is both a semi-synthetic fabric formerly called viscose rayon or rayon and a solution of cellulose xanthate produced by treating dissolving pulp with aqueous sodium hydroxide and carbon disulfide used to spin the viscose rayon fiber. Byproducts of the production process include sodium thiocarbonate, sodium carbonate, and sodium sulfide. Viscose rayon fiber is a soft fiber commonly used in dresses, linings, shirts, shorts, coats, jackets, and other outer wear; it is also used in industrial yarns (tyre cord), upholstery and carpets. It is also used in the casting of Cellophane.
Viscose yarn is yarn made from a cellulose base. It has a number of properties including a high tensile strength that can make it suitable for knitting and crocheting projects. It may also be labeled as rayon or viscose rayon yarn; viscose is actually the processed cellulose base used to make rayon, and is not itself a fiber.
Viscose rayon was the first manufactured fiber. It is not synthetic like polyester, because it is made from natural materials, but it is heavily processed. There are several production techniques used to turn viscose into rayon. The finished product has a high sheen, is very soft, and is also quite strong. However, viscose can also be brittle, is prone to pilling, and needs to be washed with care to avoid scratching or otherwise damaging the fibers.
One advantage to viscose yarn is that rayon takes dyes very well, allowing knitters and crocheters to work with a wide variety of colors. The sheen usually carries through, leaving colors deep and brilliant. In addition, the fiber retains dyes and should stay bright and colorful throughout the life of the products made with it. Crafters who want to work with bold, colorfast yarns may choose this yarn for their projects.
A key disadvantage of viscose yarn is that it doesn't have the elasticity associated with many other fibers. This can make it challenging to work with for people who are unfamiliar with the fiber. The lack of elasticity can also make gauging challenging for knitters. Crafters who have not worked with this yarn before may want to try a small test project with the yarn to familiarize themselves with it.
It is possible to blend rayon with other fibers. A number of companies produce rayon blends with cotton, silk, linen, polyester, and other fibers. Blends bring out the best qualities of the two or more fibers involved. Viscose yarn is available in multi-stranded versions that can integrate metallic threads and it is also available in the form of ribbon and other novelty yarns. As with other yarns, it is advisable to buy all the yarn needed for a project at once and to confirm that it is all from the same dye lot. This will reduce the risk of subtle color variations that might ruin a finished project.