I plied my first spindle-spun singles yesterday. I made a plying ball and spun from that. I thought I would spindle-ply it but I didn't like doing that. So I plied it on the Tina. It is very under-plied as you can see from the photo. My concern was that I wasn't going to be able to fit it all on the bobbin. So I was looking more at the bobbin and my plying ball than on the yarn I was plying. I will run it through again to add more plying twist. But I am going to do it on the Hansen, which has larger bobbins.
As you can see, the diameter of the yarn varies from worsted/bulky to laceweight. There is also a lot of yardage. I have to find the right pattern for this. All of this was spun on my Bosworth spindle and this is the fiber I learned to draft and spin. Hence the thick and thin nature of it. You've seen this fiber before. If you look at the posts with the spindle label, the Tour de Fleece Week 1 one from last year and the Mixed bag of goodies post have pictures of the fiber and the spindle.