One way to get nice three ply is to Navaho ply, and this is pretty easy, but this article deals with taking three singles, and plying them all together in one big, brave shot. I wanted to make a three ply yarn, with three colors, so I began by choosing some colors. These batts are wool and soysilk blends I made on the drum carder.
The step up from two ply to three ply is not an easy one, but well worth the effort for many projects that require strength and durability. Socks for example are excellent projects for introducing extra plies. One might even do yarn for the heels and toes in matching colors, only three ply for added strength.
There are a few pitfalls I found moving up to more than two plies, and I thought it would be nice to share them. Not everyone will have these problems, but I think many spinners may the first few times.
The plies obviously need to be more than three times the total wpi you will want for the finished yarn. I say more, because when you ply the singles together, they will fluff up a bit, so if you wanted a 13 wpi yarn, you would really need at least 40 to 45 wpi singles. Daunting, I know for those of us who are not lace spinning fools. Patience will get you there however so don't despair. There is no rule that says you can't knit or crochet some nice fluffy slippers with the first couple of skeins, if this light of a yarn isn't within your forte. You might try for a 6 or 9 wpi three ply first, then you only have to get singles around 20 to 30 wpi. Just try to get a few extra wpi above your target, but if you don't get that, it's not a problem, you can still use the yarn, and you will have learned a lot about spinning technique.
The singles need to have more twist for best results in a three (or more) ply. A two ply single with 6 twists per inch looks lovely and lofty, but the three ply seemed too floppy, although this could be a personal preference. I found I needed at least 10 twists per inch to get a good solid three ply that looked nice, and more would probably be better, depending of course on how fine the singles are spun.
On top of that, you will also need to try for very even yarn, unless you want a novelty look. For some reason, two ply looks nice with fat places here and there, but I found it very out of place in the three ply. Two small, well spun yarns, with one big fat blob, it just looks wrong to me, and the blobs never seem to match up, or make any sense. So it always looked like one singles had a mistake, while the other two in that spot were perfect. I spun a couple of samples the "normal way" just by keeping the plies separate.
Plying three yarns is only one more ply, but that one extra ply can make you want to gouge out your own eyes, or someone else's, if they were to casually comment something uh, less than complimentary. You might try using a hole punch and some heavy plastic such from a milk jug or cardboard. Punch three holes in the plastic, then thread each singles through a different one. Ah, much easier, and it keeps the plies all orderly and obeying your command. You could also use one of those shaker things on top of some of the spices such as Italian seasoning. This was MUCH easier! Make sure to clean it well first.
Finally, I would suggest you try to keep your plying very even and consistent throughout the yarn. Again, it just looks worse if one area is over plied, then the next area is a little under-plied, and finally a place where it's just right. I found that it was well worth the effort to check the balance often and keep it as even as possible. It seemed again that the extra ply showed off the tiniest little errors with a glaring consistency that was disturbing. I have issues with this sort of thing, so you may not have any problems at all!
That being said, this can be a pretty challenging step to take, so get comfortable with two ply first, but if you want to try, there's no harm in giving it a shot. If you get frustrated though, just put it aside for a few weeks and try again. It took me over a month to get something I really liked. You may do much better than I did though.
I found spinning each ply a different color made the spinning go faster and reduced boredom. The effect is very colorful, and even odd colors together seem to work. I made several sample skeins to show you, and really I like them all.
All you have to do is, trying to follow the above suggestions (if you choose), spin three singles, each a different color. Then you ply them together. The finished yarn is very colorful, and has a really neat kind of lined look when skeined, or laid out. Spin several small samples of just 10 yards or so to get the feel for how you like the colors. Then you can change them around, or choose new ones if you would like to make a change.
If you are really adventurous, you can try spinning two singles of different colors, with a S twist (counter clock wise) then ply with a Z twist. You will need to spin the singles, and ply them very, very tightly. Then take this yarn, and ply it back in with two other regularly spun singles in different colors, or other plied yarns. The plied area looks sort of like a checker board. They do this when they make the lovely mecates from Eye on the Industry. I thought, why not do it on regular yarn? You can, and with some time and sample spinning you can come up with some really pretty results.
These tend to get a little busy with too many colors, especially for a knitted project, but could we not do this for trims, purse handles or other places where a pretty and strong cord would be just the thing? What about fringe on a special shawl or scarf? It would look spectacular! I can see a lot of uses for these pretty yarns with the checker board sections. Maybe I'll even try one out of horse hair, and use it for a leash for the dog, or a lead rope for the sheep. Maybe I'll even try to make a mecate of my own someday, but I'm not ready for that degree of skill requirement yet... It is not for the faint at heart.