Hoo boy, it's been a while since I posted a good, solid, technical article.
(Just in case you are wondering — yes, this does mean that my personal UFOlympics are sort of at a standstill. I've spent a lot of time working on #5, the Rowan vest: trying to figure out how to trim out the armholes without adding too much bulk. I've tried about 4 different things so far, and I really thought I had it nailed on the last attempt, but not quite. So I'm ignoring it for now. More about all that later.)
So, you were asking — just how do you join on a new ball of yarn?
Here again we use the All-Purpose Knitting Answer: Well, it depends…
Joining yarn – the basics
There are two types of situations in which knitters have to join yarn, and not all techniques work in both cases.
One case involves joining the same yarn, as when reaching the end of Ball One and starting Ball Two. Also in this category is when you find a knot or other imperfection in your yarn that you need to eliminate.
The other case involves joining a different yarn — another color, or a different texture.
No matter how pricey the yarn, you may come across a “manufacturer’s knot”. Be aware that these knots are not designed to hold up over time! They are only intended to get the yarn through the manufacturing process. If you knit through these knots, they may fail later — especially after washing.
Additionally, if you just knit away, pretending it's not there, you have no control over where the knot ends up or how it looks. You should always break the yarn, eliminate the knot (or any other imperfection), and join the yarn again to your satisfaction.
(Oh, c'mon, it's not that hard — and the potential long-term cost of not doing it certainly outweighs the short-term benefit of not doing it. Just decide, right now, that you're always going to do this — and you'll be a better knitter.)
Knotting the yarn on purpose is a subject of much controversy. It depends mostly on personal preference and the final effect on the work. I really have nothing against using knots to secure things when finishing a piece, as long as they don't make it look like crap. To that end, either a square knot or a surgeon’s knot makes a neat, secure knot.
BTW, I'm not sure where or when I first learned the "surgeon's knot", but initially I learned to tie it by doubling the second throw. Within the past few months, I've become aware that most sources show that you are supposed to double the first throw. This makes a bit more sense, because it holds the initial knot tight while you tie the second knot.
Oh, well. "My" version seems to be holding up pretty well, as far as I know. I haven't tried doubling both throws, but someday I will, just to see if it might be even better. (I'm pretty sure that's uncharted knot-tying territory, because surely all those surgeons wouldn't ever have thought of trying it.)
Finally, always leave generous tails (6”) when joining yarns, to make life easier when it comes time to weave in the ends.
When knitting flat
Opinions vary as to where it is best to join new yarn when knitting flat. Some say always at the side of the piece; some say never at the side of a piece.
I'm really not sure why anyone would say that you should never-never-ever join yarn at the side of a piece, although I know I've seen that stricture in print — unless it's because of fear that it will make the seaming difficult.
My take is to use your judgment as to how it will affect the finished product — mainly, how easy it will be to disguise the join later. For example, in MOHAIR, you can do just about anything right smack in the middle of the front, and it's easy to hide under all that fuzz — but in cotton, it is much harder to weave in ends discreetly.
Of course, when knitting in the round, you have no choice to join yarn at an edge — but you can put a join, say, under an arm instead of front and center.
Joining the same yarn
1. Working doubled stitches: Let the old yarn end hang to the right. Pick up the new yarn and hold it together with the old yarn, with its tail hanging to the left. Work anywhere from 1 to 7 stitches with both strands. (The number of stitches to be worked doubled varies with yarn type, gauge, and which authority you consult.)
Then drop the old tail and continue working with the new yarn. When returning to the doubled stitches, be sure to work both pieces of yarn as one stitch.
Continental knitters may find it easier to hold the old yarn tail to the left and the new yarn tail to the right.
2. Spit splice: For yarns that can be felted. Break both ends of yarn so they are wispy.
Moisten each yarn end, in any way you see fit: you could squeamishly go get some actual water, or you could use a convenient, organic, gentle enzymatic solution.
Lay both tails in the palm of your hand, heading opposite directions, overlapping the wispy ends. Rub your palms together to create heat and friction.
(For the record, Sandi thinks this one is totally disgusting.)
3. Regular splice: For plied yarns. On each tail, divide the plies in half and cut off half the plies a short distance from the end. Retwist the half-ends together to mimic the original yarn thickness.
This is kind of the "old standard" way of doing it, and I include it for completeness — but I don't like it, and I don't use it. It's not neat, not elegant, and those little ends of the plies are always sticking out.
4. Sewn splice: For ribbon yarns. Sew the old tail to the new tail with a few handstitches and matching thread. Bonus: no ends to weave in.
Fabric glue can also work, although if you choose to go this route, you must promise me you'll never hold the bottle of glue over your project and squeeze. This can be bad bad bad bad. Instead, squeeze some glue out onto a piece of paper and use a toothpick or something to apply the glue, for sheep's sake.
Joining a different yarn
The biggest concern here is with keeping the tension correct across the yarn change.
Note that all of these techniques can work when joining the same yarn, too — although in some cases, such as technique #2, it's probably not worth doing — unless you find later on that the doubled st is noticeable.
1. Start working with the new yarn: Just what it sounds like – i.e. do nothing special, and let the join be all loosey-goosey. Later, adjust the tension around the join, and tie a knot to secure if desired.
2. Working doubled stitch with both yarns: Work one st with both yarns; pick the unwanted yarn out of the doubled st afterwards when weaving in the ends.
3. Tying on: Use the new yarn to tie an overhand knot around the old yarn. Slide the knot up to the work. Proceed with work. Later, untie the overhand knot, and tie a neater knot if preferred.
Tying on is pretty much the best technique, IMHO. Neat, quick, easy, effective. Works when joining the same yarn, as well as when joining a different yarn. If you're only going to learn one way to do it, this would be a good choice.
4. Working doubled stitch with tail: Insert needle into next st, wrap new yarn around it, and work the st. (It will be loosey-goosey.)
For the next st, pick up the new yarn together with its own tail, and work this st with the new yarn doubled. Then drop the tail and continue working. When you return to this doubled st, be sure to work both pieces of yarn as one st. Once you have worked the doubled st off the needle, you can tug on the tail to tighten the loose st.
This one is a firm, solid join, but it doesn't work well in the middle of a row. It's best suited for joining a new yarn at the beginning of a row, on the edge of a piece. When used in this way, it does keep the edge from being all loosey-goosey, which can be a real boon when seaming.