Viscose is a man-made fiber—a “regenerated cellulosic fiber” made from cellulose, most commonly wood pulp, but many plants can be used, such as bamboo.
It is not a synthetic fiber made from petroleum. The cellulose is broken down, and then “regenerated” into a fiber. All viscose is made from cellulose. And only cellulose. Viscose is a fiber - not a yarn or a fabric.
In making the viscose you can make it by not paying any attention to the resulting pollution OR you can make it in a “closed loop” system, which captures / neutralizes / re-uses the nasty chemicals, and treats the water so no water pollution—innovative, circular, and regenerative. (There is still air pollution).
Tencel, lyocell, micro-modal, modal, rayon, and bamboo rayon are all viscose. They are just brand names (or old brand names which are now used to distinguish tweaks in the process. Technically, tencel is a lyocell viscose fiber).
You can make yarn from combining numerous kinds of fiber into the same yarn. It’s called an intimate blend. But 100% viscose yarn is made from 100% cellulose.
One of the major advantages of viscose over synthetics is that it is biodegradable.
In the viscose process, cellulose is treated with caustic soda (aka: sodium hydroxide) and carbon disulfide (which can cause nervous system damage). This process converts the cellulose into a highly viscous liquid about the color and consistency of honey. Think of making papermache. Then the mixture is forced through fine holes in a spinerette (think shower head) which produces long filaments of yarn. These yarn filaments are dumped into a chemical bath of sulfuric acid which hardens the filaments, the viscose yarn.
When bamboo viscose was introduced a few years ago, it was a big hit, and American synthetic yarn manufacturers correctly pointed out that the process can be extremely polluting. The environmental burden comes in disposing of the process chemicals: the sodium hydroxide, though not toxic to humans, is harmful to the environment if dumped into our rivers as untreated effluent. Carbon disulfide is toxic to the nervous system; and sulfuric acid is a component of acid rain. There are emissions – air pollution - of these chemicals as well, which contribute to greenhouse gasses.
These chemicals do not necessarily remain as a residue on the fibers. Viscose can be Oeko-Tex certified, a certification which verifies that the finished fiber has been tested for and contains no residual chemicals which may be harmful to health. Sadly, GOTS does not yet certifiy cellulosics, so the best 3rd party certification right now is Oeco-Tex. Oeko-Tex certifies only the final product, i.e., the fibers or the fabric. It does not examine the production process, which is where most of the environmental burden is found.
We always use closed loop viscose. We often use bamboo as our source of cellulose for our viscose. Viscose from bamboo is anti-bacterial, anti-fungal, and is hypoallergenic.
We have mentioned some of the (considerable) negatives of the production process above. Positives include the fact that bamboo is one of the fastest growing plants in the world, absorbing about 5 times the amount of carbon dioxide as an equivalent stand of trees. Bamboo grows with no irrigation and no pesticides or synthetic inputs. And currently there are no known genetically modified organisms (GMO) variants of bamboo. We have ensured that our bamboo does not come from stands that endanger panda habitat.
We decided that the addition of bamboo to the world’s fiber set was a positive development, and that the positives outweighed the negatives. It is important that bamboo come from FSC (the Forest Stewardship Council) certified stands, important now given the sudden popularity of bamboo for fabric. Some (not yet all!) of the bamboo viscose fiber we use is produced in a process that has no water pollution or solid waste disposal problems, and that has only minimal air pollution.
TwoSisters offers a collection of viscose fiber fabrics. We believe that this is the future for responsible textiles. Synthetic fibers, including recycled polyesters harm our planet and damage our waters due to microfiber shedding.