So far my spinning accomplishments have limited myself to singles (one-ply yarns) for multiple reasons.
One is that I adore singles for their neat, sleek appearance and the wonderful stitch definition you get from them, as well as the beautiful way colors pop on a single-ply strand. Witness!



Another reason I have remained single-ply is that within my current range of spinning equipment, plying any decent length of yarn is a really royal pain.
So why ply at all? F&%$ it, right?
Of course not. Art is about SMASHING YOUR LIMITATIONS!!!
Spinning a single requires allowing enough twist to enter the fiber so that it has some strength and doesn’t just fall apart. The twist increases the density of the fiber, making the strand firmer the more you twist it. This means that a really strong strand or ply is going to be pretty firm as well – and why would you want to stitch up clothing that feels like a bunch of rope rather than cushy, soft yarn?
Of course, as illustrated above, there are plenty of single ply yarns that are more than adequate for making cushy soft things. Plying is merely one way to balance strength and fluff – allowing 2 plies of fiber to unleash some of their twist energy by winding around each other fluffs them up while combining their strength.
I came to fully realize this concept when I began to spin a sample piece of Targhee roving. I’ll save my rave reviews of this breed’s fiber for another post – for now I’ll just say that I spun it fairly thin (which was easy because this stuff is AWESOME.. ahem). But, damn, the spongy wonderfulness of this wool didn’t seem to translate into my spun single. It was just too dense.

Since this was just a sample yarn I was doing for fun, it seemed like the perfect opportunity to try out Andean plying, a method of producing 2-ply yarn using only one strand of 1-ply, using (as far as I can tell) some sort of weird mountain shaman yarn magic.
Just kidding. The Andean ply wrap is really not as complicated as it looks, once you try it out.
This special way of wrapping allows you to feed the two opposite ends of the single strand onto your spindle at once, plying them together.
WARNING: Wrap loosely, for the sake of your digits. My tension was not relaxed enough and by the end my middle finger was purple and felt like it was going to fall off, which would suck, because that is my favorite finger.
Once I had that conquered, I plied my yarn, making sure to spin my spindle in the opposite direction (clockwise) that my single ply was spun (counterclockwise). Spinning clockwise produces what is referred to as an “z” twist, while counterclockwise is referred to as “s” twist.

Success! What was once a very firm single that would have made a terrible hat was transformed into a soft 2-ply, retaining the bouncy charm of the Targhee fiber but with the strength of a single. It would make a great hat, if I had more than 40 yards of it. Maybe that will soon be remedied.
-MF
P.S – I knitted up a tiny swatch just to see what it was like. As this great article from Knitty Spin attests, handspun does indeed have an energy unique and different than machine made. Mine was practically leaping off of my needles! Interesting.