Bamboo is the biggest red flag in sustainable fashion, and a natural swimwear maker will tell you why. Bamboo is woody and tough, the stuff of mats and scaffolding, not thread. To turn it soft it has to be dissolved in carbon disulfide and rebuilt as viscose rayon, so bamboo viscose is not a natural fibre and not a natural process. Sitting in the workshop with Vivi Rufino and David, the couple who run Freedom Ecowear, Vivi names it as her number one greenwashing trap, plus the other red flags the two of them watch for.