I've been experimenting with singles recently, and wanted to share some of my findings with you.
A few years ago, I was at a spinning workshop and the instructor was demonstrating how to spin a singles yarn. I asked a somewhat silly question: "How much twist do you add?" The (in retrospect) obvious answer was: "As much as you need to hold the single together." Seems pretty simple, doesn't it?
But this answer gets to the first, and in my mind, most important issue in successfully spinning singles: fibre choice. You want to start with a fibre that will stick to itself, so no silk or alpaca or plant fibres need apply. You also want a fiber that has at least a medium staple length, just for ease of spinning. If you're new to spinning singles, you'll probably be happier if you leave the merino aside for this round.
I started with some Corriedale in the Parakeet colourway.
I stripped the top into pieces that were approximately 0.5 in/1 cm wide and spun them using a short-forward draw. I find that the key to getting the right amount of twist lies in slowing down and using a lower ratio then I usually use. I had to make sure to treadle relatively slowly while I drafted, trying to insert enough twist to keep the single integrity without getting sections that were overtwisted.
This is the skein fresh off the niddy noddy - definitely not balanced! You can see that it's not the most even yarn ever - there are narrower sections with more twist, and puffier sections with less. This just shows how spinning a singles yarn is a really good way to see how twist gathers in areas with fewer fibers and jumps over thicker sections. If you are even a little bit interested in trying out art yarns, this is good practice!
Now, the next important step for ending up with a usable singles yarn for knitting is in the finishing process. I like to use a fulling finish to my singles yarns, allowing them to felt ever so slightly to help hold the single together.
This process requires two containers of water - one hot and one cold, both with wool wash if you like (both containers in the picture have wool wash, even though only one is sudsy). Put the skein into the cold water and let it get wet.
Once the skein is wet through, transfer it to the hot wash and gently agitate the yarn. Now, I know that usually, as handspinners, we are doing everything we can NOT to agitate the yarn, but this is one time that you want to move the yarn around.
Give it a few stirs (with hands or an implement, however you like - my Speshul Snowflake hands don't like the hot water direct from my tap, so I use an old wooden spoon), and then pick it up out of the hot water and let as much hot water drain off into the bath as you can. Give it a squeeze if you like, then drop it down into the cold bath and gently agitate again.
You'll want to repeat this process from cold to hot to cold to hot to cold several times. As the fibres begin to full, you find the strands of the skein beginning to stick to each other a bit.
When you reach a point where the strands are clinging together but still easily pulled apart, it's time to stop. Put the skein into the cold bath and let it sit for a few minutes without agitation. Then take it out, squeeze or spin out the excess water, and let it hang unweighted to dry.
I ended up with about 100 yds of floofy singles from 2 oz of fiber (800 ypp) - about aran or worsted weight. I was hoping to have enough to knit up another topdown hat, but it might have to be for the kids instead of me.
I hope this has been helpful and/or interesting. Please post in the comments with any questions or experiences you've had with spinning singles.