Monday, January 26, 2015

Warmth, again and again

If you want real warmth in clothing, it needs to block air flow like a fine bed sheet.

With knit wool that means lots of twist in the yarn, and yarns knit tightly together.

Lots of twist means very fine plies. For most things, I like singles of ~5,600 ypp.

Then I do not ply yarn very tightly, so that as yarn is knit, the yarn deforms and "fills" all gaps.

The commercial yarn that this concept is built on is the old Lions Brand Fisherman's Wool.  This yarn is no longer made. Production was moved to China, and the new  Lions Brand Fisherman's Wool is different.  The new Fisherman's Wool is much more pleasant to knit, but the resulting fabric is not as warm or durable.

To block air flow through the yarn, the wool fibers must be between 20 and 40 microns apart.  Closer and they tend to conduct heat. Farther apart and air flows between the fibers carrying heat.  Keeping fibers that close together takes a lot of twist.

For wet weather, I like long wool, spun worsted at 5,600 ypp.  Twist is about 9 tpi. These singles get loosely plied up into a sport weight (1,000 ypp) yarn.

Once you get below freezing, things can get really cold.  There, I like fine wool, spun woolen at 5,600 ypp and 12 tpi. These get plied up into 5-ply at 1,000 ypp or Aran weight at 500 ypp for Arctic  (or Antarctic) conditions.

Ok, these yarns are a bit of extra work, but they are warm, and nothing is worse that being really cold.

The the yarn needs to be knit so tightly with fine needles, so there are no gaps in the fabric.

If you knit with 2 or 3-ply yarns there will not be enough twist to hold the individual wool fibers close together and the wind will blow right through the yarn.

If you use a 5-ply with enough ply twist to hold the yarn round, then there will be gaps between the yarn and the wind will blow through the fabric carrying heat away from the body.

Hand spun, hand knit fabrics can be so warm that they feel like magic.  Most do not make the cut.

1 comment:

Purl Mary said...

Totally with you there. Nothing worse than supposedly warm knits that let the wind through. I don't care how pretty they are, they don't keep the coled out. So now, I try to spoin and knit for warmth, which means high twist and small needles, and hang the pretentious claptrap.