There are several different processes for making rayon. All rely on modifying cellulose to make it soluble in a chemical called the spinning solution. This solution is pushed out through a device with a specially engineered opening, called a spinneret, and the resulting fiber is rayon. Some rayon can be laundered and some should be dry-cleaned. The difference is in the arrangement of the polymers within the fiber and the varying wet strengths that result.
Cotton is cellulose, and cotton is actually stronger wet than dry.
The alignment of polymers in the wet stage is stronger and shares the load better. In some forms of rayon, like viscose rayon, the components of the fibers move farther apart when they are wet and lose strength, Dr. Obendorf said. In newer kinds, like Tencel and Vantrel, there is a different arrangement of polymers within the fibers, allowing them to be washed. New questions are answered on the site every Tuesday and Thursday.