The Helium series of three cardigans I'm currently working on involves knitting with lofty, airy yarns at looser gauges. Quite apart from the fact that weaving in ends is a pain, for the two cardigans in Lett Lopi and Shelter, splicing the yarn joins makes for a more beautiful, uninterrupted finished knitted fabric (splicing is simply not an option with the slipperier Silk/Mohair). Both Shelter and Lett Lopi are perfect for splicing since they are spun from wools that easily felt, with "sticky" fibres that cling to each other. At first I wasn't quite sure how to splice the Lett Lopi--it appeared to be a single ply. Then I learned that it is actually lightly spun from two strands of Plotulopi (the unspun icelandic wool, made famous by Meg Swansen). Even though it looks as though it is a single ply, in reality there are two strands which can be separated and therefore spliced. Here's how to do it for either Lett Lopi or Shelter:
1. Break, don't cut, both ends that you wish to splice. Breaking will leave nice tapered ends which will meld into the splice.
2. Separate the two strands that make up each end, then break off one strand of each so that the ends are staggered.
3. Intertwine the ends of the strands, like this below.
4. You probably don't want to do this next bit in public. Spit or lick the palms of your hands, then vigorously roll and rub the overlapped strands into one. It will start out like this,
but very quickly will felt into a strand very like the rest of the yarn.
5. Proceed to knit with your newly joined wool. I don't recommend splicing in areas where extra strength is needed, like underarms or bind offs. Otherwise, just carry on and enjoy the fact that you have magically joined two ends of wool together.