Viscose is rayon and yes, it's not a strong thread at all. Really, any area that is going to be in contact with a chair or rubbing shouldn't be embroidered with it. (Like jeans pockets, sorry to say!) I have a good example, one lady spent hours and hours doing beautiful embroidery on her skirt and soon began to notice areas on her skirt had lots of thread breakage. Guess where those areas were? ;> I'm actually phasing out all of my rayon and not buying it anymore(this includes Sulky). I'm only buying polyester embroidery thread now, like Isacord. Rayon is also not colorfast in the wash using any kind of bleach product. Young mothers with babies bleach their clothes and blankets a lot and all that fancy embroidery may end up stained and or different colors.