Bamboo viscose is soft, comfortable and warm. BAM mix it with cotton for, it says, a better ‘feel’ or handle. What I’ve found is that the garment keeps its shape better than 100 per cent bamboo viscose ones. I was concerned that the cotton would make the garment cold when damp but this hasn’t been a problem. Like wool, bamboo viscose is absorbent, with the layer next to the skin staying dry most of the time. When it does get damp it dries fairly quickly but isn’t as warm or comfortable as wool. The fabric is quite thick (this is the heaviest garment tested) but is surprisingly cool in hot weather. Bamboo is naturally antimicrobial and the top doesn’t smell after several days wear. The addition of elastane means the garment stretches and is close-fitting. It has a snug and warm high collar and a short zip for ventilation. There are thumb loops that are useful in cold weather, preventing a gap with gloves. The sleeves can be pushed up in hot conditions. As well as a next to skin layer this top also makes a good second layer over a thinner base layer.
Bamboo is grown without pesticides or insecticides and is of course biodegradable. Chemicals are involved in turning it into viscose but overall it seems more environmentally friendly than many fabrics.