Cotton Bam Boo 52% Cotton, 48% Bamboo Cotton Bam Boo is a smooth, lustrous sportweight yarn with great stitch definition. The cotton component allows the blend to knit up into a fabric that is soft and breathable. Bamboo viscose adds a soft sheen, and it is naturally antibacterial. The cotton/bamboo viscose blend gives this yarn a wonderful drape – perfect for summer shawls and wraps.