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However, you can and might want to consider the end-use for your yarn and the technique you’re going to use to get there.
Crochet prefers the final twist direction to be Z, since it adds Z twist to a yarn. So, if you were to take a final S twist yarn and crochet it, you’d be taking twist out ... and if it were singles, this could be a mess if the yarn then drafted apart again.
Knitting depends: British/throw-style knitting typically adds Z twist and German/Continental/pick-style knitting usually adds S twist. If you are doing twined knitting, your two strands will wrap around each other too ... no spinning style I know of can conquer that, except perhaps one of those yarn-ball-wrist-holder thingies that might let the ball unwind as you go, if you are working your Tvåändsstickning from both ends (grin). But I did note that S singles, Z ply is the recommended yarn for that method of knitting.
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Nalbinders tend to disagree ... I used Z twist and did well with that, as my stitch technique added Z twist, but others report their technique adds S twist.
Now, for Kumihimo, Embroidery, Needlepoint, Cross-stitch, free lace, bobbin lace, hairpin lace, Tunisian crochet ... I’m afraid you’re on your own ;-)
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ETA: You can tell the top is spun Z because the plied-back sample plies back S (the slant on the plying twist matches the middle bar of the letter S). And the lower is spun S, as the plied-back sample plies back Z -- the slant of the plying twist there matches the middle bar of the letter Z.
The yarn is spun from Three Bags Full Turquoise roving, spun S, plied Z with turquoise thread strung with real copper beads, and then plied S on another strand of Z-spun Turquoise. Whew!
If you've found direction of spin helpful in your fibery pursuits, I'd love to hear about it, especially if you can enlighten me about spinning for embroidery and the other methods. Thanks!