From the Spindlers group on Yahoo!  This is freaking me out with natty detail that I’m not sure matters.  I typically spin counter-clockwise, which according to the Interweave handouts is S, but I should try it the other way (clockwise = Z) and see if it works better one way or the other.

If you want a really shiny woven fabric, you want the warp spun one way and 
the weft in the other.  All the twists will line up that way.

> > Also I remembered reading once upon a time or hearing that ‘we’
used to spin S but later it was changed to Z – why?

> I really don’t know, I’ve never heard that. If it had to do with
> knitting, I would assume that it is connected with knitting singles.

++ Actually it was in Roman times 😉 sorry for not writing it out.
Apparently before then we ‘did it’ the other way around. I shall
delve deeper and see if I can get more details.
>
> I find it impossible to notice any difference in knitting, crochet,
> and weaving….BUT. ..

++ I have a thought here – you wrote that the effect is not one that
you notice so much – MAYBE just maybe – my thought here it depends a
lot on how much twist your yarn has from the start wether it’ll be be
something that’ll make a difference one way or the other.

> I do notice the difference in embroidery, with wool, and am sure
that would be so in something like tatting and naalbinding.

++ Nålbinding is something I have done a little, YES it matters a
great deal here. Which is why I love working with singles 🙂 such as
Lopi.

> If you carefully spin a worsted yarn, and then rewind the bobbins so
> that you are plying from the end that you started spinning, and then
> rewind that so that you are working from the end that you spun and
> plied [still talking about the spin of the ply being opposite the
> direction it was spun in]. All those little bits that look like the
> shape of a pine tree, like you said, are all going the same
direction instead of different directions. The result is a thread that wears
> much better with constant rubbing, like embroidery. It is very
> directional, and works from the end you started with. I have heard
> this called "crewel spinning", for crewel embroidery.

I do believe I will try S spinning instead of Z. I make tatted lace
and all of the commercial threads become tangled because there is so
much twist in it. I think that where S would make crochet more
manageable, it would make needle lace and tatting more manageable.

Early wheel spun yarn was at one time deemed to be too soft for warping a loom.  In order to difference spindle spun from wheel spun, spindle (Hand spun) was to be done Z and plied S, while wheel spun was to be done S and plied Z.
Since most is now wheel spun, it is predomiately spun Z and plied S.

            Having recently begun a hairpin lace project with my spindle spun
merino I can relate what’s happening so far. Since hairpin lace is a
new skill I spun one ounce of merino and made the first strip to see
how it works. Almost immediately two things were clear: hairpin lace
builds quickly, the twist was unwinding. It wasn’t enough to take it
for a re-ply though I seriously considered it. I’m not sure it’s a
factor of both the crocheting that takes place and the flipping of the
loom. The next ounce will be spun widdershuns then plyed clockwise to
see if it makes any difference.

            The general assumption is that Z spun yarns are more suitable for
knitting and that the crocheting process removes twist in the yarn so
that you are better to spin in a counterclockwise direction.

As a historical matter, yarns that were spun S were probably bast
fibers.  Technically you should get a smoother yarn when spinning hemp
and linen in the same direction as the fiber grows.  If you remove a
tiny thread of hemp or linen and place it in warm water it will curl to
the left.  Most but not all bast fibers grow this way and are therefore
better spun S to yield a smoother yarn.

This makes no sense to me, because (assuming it’s true) if you turn the fiber over, it would be curling to the right, right?  Must experiment.