A blend of polyester and viscose can be hand-washed in water at 30 C using a neutral soap. Some polyester-viscose mixes may be washable on a delicate setting in a washing machine using a detergent formulated for delicate fabrics.
Viscose fibers become weakened and tend to break down when they are wet. While the polyester content in the blend is rugged enough to wash in the washing machine on a regular cycle, the viscose fibers, which consist of cellulose derived from plant cells, are not as durable.
Garments made of a polyester and viscose mix must never be dried in a dryer or spun or wrung to dry. They should be hung up on a clothesline or laid flat to dry when they are still soaking wet. The viscose content retains water, so it is likely to take a while to dry thoroughly.