The idea of soy used as a vegetable fibre like linen or cotton is not new; it dates back to the 1940s, when Henry Ford spoke of the virtues of soy and was photographed wearing a suit of fabric woven from it. However, to most spinners, handknitters, and weavers, the concept is a fresh and rather bemusing one.

Soy silk, so named because of its filament fibres (structurally similar to silk, as opposed to staple fibres in wool, linen, and cotton), is a recent innovation from the South West Trading Company, which owns the trademark in North America. The fibre is made entirely of soy protein, a by-product from the manufacture of tofu; the liquefied protein is extruded mechanically, then cut and processed like any other man-made fibre.

The fibre, made in China, is sold as a top for spinning, dyed or undyed, or as yarn which takes the form of a knit ribbon, naturally coloured or in one of a number of colourways.

Handspinning raw soy silk is much the same as working with tussah silk, and yields similar results. The finished yarn is inelastic with a fairly crisp hand, though it softens with washing. Undyed, the fibre is ivory-coloured; it takes well to dyes, though careful attention is required if natural dyes and mordants are used instead of chemical preparations.

Currently, prepared pure soy silk yarns for sale come in three varieties: "Oasis", a midweight ribbon (the recommended gauge is 5 stitches and 8 rows to the inch); "Phoenix", which is the same but slightly heavier (knitting up at 4 stitches and 6 rows to the inch); and "Infinity", a fine yarn for lacework. When knitted, the fibre has a smooth sheen like mercerised cotton or silk, and a drape similar to linen.

Because it is entirely recycled, soy silk has been embraced by environmentally-minded spinners and knitters. Though reusing resources that would otherwise go to waste is undoubtedly a worthwhile endeavour, it also means that soy silk tends to be more expensive than comparable yarns in more traditional fibres; as it stands now, a 200-yard skein retails for about $13 US, just enough to give pause for thought before purchasing.

Soy silk is certainly novel and interesting, but as a fibre for working with regularly it has no advantages over linen or silk, save for perhaps value as a conversation piece.

Sources:
"Soy Silk". South West Trading Company. www.soysilk.com
Yarn Profile: Soy Silk Phoenix. Knitter's Review. http://www.knittersreview.com/article_yarn.asp?article=/review/product/031009_a.asp
Also, the ballband literature that came with skeins of "Phoenix" and "Oasis" (as well as what came with a shipment, after considerable wheedling and pleading with the proprieter of a Nanaimo woolshop), and a week spent spinning and dyeing and knitting the stuff.