For anyone who knits in the round (top down or bottom up) you have probably encountered the problem of joining new yarn without it showing. With flat knitting it is just a matter of finishing your yarn at the end of a row and all ends can be hidden in the seams. Knitting in the round means that you need to be a bit more inventive.
My two favourite methods of joining are a Felted join and a Russian Join.
The felted join can only be used with an animal fibre. You need to split the end of the old yarn and the new yarn into two pieces for a couple of inches. Then layer the two sides together like a yarn sandwich and give it a gentle twist. Now wet your fingers (if you aren’t too squimish you can spit on them!) and dampen the yarn making sure they are all a little damp. Beware of getting stray hairs in your mouth. Then roll them quickly between the palms of your hands and the friction will felt them together. Truely magic.
The Russian Join can be used on all sorts of yarn, animal and plant based. However if the yarn is very splitty it won’t work very well (if the yarn just unrolls in your fingers). Thread the end of the working yarn through a tapestry needle and work the tail down onto itself in the working yarn. Try to keep it towards the center and work for around 2 inches. Before you pull the needle through pull the start of the new yarn through the loop created. Now do the same with the new yarn. Pull the yarn flat, trim any loose ends and keep knitting.
If the yarn you are using is very thick you may find that the Russian Join creates too big a lump in your knitting. In this case you can try splitting each end of yarn in half and cutting half of the yarn. This means that there is less bulk being woven through.
My camera battery is dead right now so I can’t add photos but you can also take a look at the Russian join here Russian Join.