Viscose fiber and yarn are basically the same as Rayon and are known as man-made silk. Although viscose and rayon are man-made and manufactured, the ingredients come from natural cellulose plant material such as wood or bamboo. If not cleaned or dried properly they can suffer the effects of cellulose browning just like that of cotton.
Viscose and Rayon rugs are also very sensitive to excessive agitation and susceptible to distortion and pile damage. When dry vacuuming viscose run your hand across the face of the rug and try to determine the direction of the nap or lay of the carpet’s face yarns. Vacuum in that direction and keep the the beater bar or brushes raised up as to not be abrasive and cause permanent distortion or damage.
When dealing with spills use a white towel to gently blot up excess liquid. Do not rub or press too hard as this can and will cause a disruption in the lay of the face yarns and may not be reversible. This may cause a pooling effect where you get a patch that looks like a pool of darker or lighter color surrounded by the correct color. You can usually identify pooling by brushing your hand over the suspect area and looking for what appears to be a change in color based on the direction you are brushing. You may also feel a physical border surrounding the area. In certain instances you can drop a pencil, eraser end facing down, on various parts of the carpet and note the direction it falls after it hits. The pencil will fall a different direction in a pooled area.
After blotting up as much of the excessive moisture from the spill as possible, it may be necessary to use a mild and neutral detergent to remove the remaining spot or spill. Mix a small drop of Dawn dish soap in a half cup of cold water and use a white towel to gently blot. Use some plain cool water to blot and rinse any soapy residue away and also to dry the area as much as possible. You can use a mix of half vinegar to half water. The longer the drying time the more potential for a problem. Again you want to gently blot and do not rub or use excessive pressure. Using cold water will help prevent a stain from setting along with other potential damage.
If you do experience a browning issue or even some pile distortion, a professional carpet cleaning company with experience in fine fabric and textile cleaning may be able to help you recover. The best chance you have is to follow the instructions listed in this article. In Northeast Pennsylvania, the Poconos and surrounding communities, call Services Etcetera Carpet & Upholstery Cleaning at 570-459-0429.