Tuesday, August 16, 2011

Fiber Thoughts: Rayon

Rayon from sugar cane.
This post will contain information on all kinds of rayon -- bamboo, sugar cane, the regular wood pulp kind.  I can hear a few of you out there saying "ka-whaa? bamboo is rayon?!"  I feel relatively certain of this because of how frequently I see threads on yarn and fabric forums announcing the "secret" of bamboo fiber.  Yes, that silky soft stuff is, in fact, rayon made from bamboo.  There is a non-rayon bamboo fiber out there, however it is more like flax, and doesn't really resemble the more common rayon from bamboo at all.

So, what is rayon?  Rayon is a manufactured fiber made from cellulose.  You can make rayon from just about any plant source, but there are three that I've seen.  The regular old standard rayon that has been around forever is made from wood pulp.  Rayon made from bamboo has been enjoying significant popularity due to it's purported environmental friendliness and antibacterial properties.  I have recently found several yarns made from rayon made from sugar cane, as well.  "Bamboo viscose" and "sugar cane viscose" mean the same as rayon.

All rayon has some properties in common.  It is a smooth, silky fiber.  Rayon has excellent drape, but not so much memory, so it works extremely well for lace applications.  It is also extremely durable, so it works well as a substitute for silk in blends that need that soft silky sheen, but also need to be easier to wash than silk.  Rayon is also (surprisingly) highly absorbent.

The main differences in the rayon types are, quite frankly, questionable.  Bamboo rayon in particular is touted for being environmentally friendly, and it is indeed more environmentally friendly than regular rayon, as bamboo can be grown very quickly with little or no pesticide or fertilizer use.  However, the chemicals used to process the bamboo into rayon are pretty toxic, and the process requires large amounts of water and energy, so it really isn't the Gift to Gaia that it's occasionally billed as.  Bamboo rayon is also claimed to have antibacterial properties.  While bamboo, the plant, is indeed naturally antibacterial, the amount of processing involved in making rayon makes it fairly unlikely that those properties make it to the final fiber.  It is possible, however I have searched extensively for the supposed study showing that bamboo rayon is antimicrobial, and have not been able to find it anywhere.  The best I can come up with are references to a Japanese study... however, the study itself does not seem to be available anywhere.  And I can read and search in Japanese.  Given that the majority of bamboo fabrics are made in China, I deeply suspect that the study is the invention of a manufacturing company.  I could of course be wrong, and if you know of a reference, please point me at it!

So, is there any difference between the types of rayon?  I like to think there is.  It feels to me that bamboo rayon and sugar cane rayon are smoother and more silk-like than wood pulp rayon.  Sugar cane rayon, in particular, has a delightful sheen to it.  This may, however, merely be a manufacturing difference, and not a material difference.  So seriously?  Know the basic properties of rayon, then use your own fingers and eyes to pick an individual yarn.  That will probably serve you better than knowing the plant source of the fiber.

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