So, how do you think they MAKE bamboo into spinnable fiber and yarn, and why do they do it?
"While specifics can vary, the general process for chemically manufacturing bamboo fiber using hydrolysis alkalization with multi-phase bleaching technology – which is the dominate technology for producing regenerated bamboo fiber – goes like this:
- Bamboo leaves and the soft, inner pith from the hard bamboo trunk are extracted and crushed;
- The crushed bamboo cellulose is soaked in a solution of 15% to 20% sodium hydroxide at a temperature between 20 degrees C to 25 degrees C for one to three hours to form alkali cellulose;
- The bamboo alkali cellulose is then pressed to remove any excess sodium hydroxide solution. The alkali cellulose is crashed by a grinder and left to dry for 24 hours;
- Roughly a third as much carbon disulfide is added to the bamboo alkali cellulose to sulfurize the compound causing it to jell;
- Any remaining carbon disulfide is removed by evaporation due to decompression and cellulose sodium xanthogenate is the result;
- A diluted solution of sodium hydroxide is added to the cellulose sodium xanthogenate dissolving it to create a viscose solution consisting of about 5% sodium hydroxide and 7% to 15% bamboo fiber cellulose.
- The viscose bamboo cellulose is forced through spinneret nozzles into a large container of a diluted sulfuric acid solution which hardens the viscose bamboo cellulose sodium xanthogenate and reconverts it to cellulose bamboo fiber threads which are spun into bamboo fiber yarns to be woven into reconstructed and regenerated bamboo fabric.
This gives some feel for how chemically intensive the hydrolysis-alkalization and multiphase bleaching manufacturing processes are for most bamboo fabrics that are promoted as being sustainable and eco-friendly."
This is the same process used for making rayon out of wood fiber. In the US, Bamboo yarn made by this process should be labelled "bamboo rayon".
Design-wise, rayon (whether from wood products or bamboo) take a nice dye, has good drape, wears well, etc. I'll keep all that in mind when I'm shopping. But I think I'll keep the manufacturing process in mind, too. And my scotch soul wants to know why I would pay a premium price for something that's half rayon.
I feel I've been a victim of marketing (Look! Green, sustainable Bamboo!), but it was my own fault. We'd all like to think we are doing things in a greener, more sustainable way. But it's way more complicated than buying some bamboo yarn.