How do I wind it into a skein? It's actually leftover from a project so it's already in a ball...but I want to dye it so it will stripe when I knit in to socks. What have you done? Can I just use a chair back???
If you want self striping yarn you are going to need to wind LOOOONG loops. You might even take the needles you'd knit the socks with, cast on and knit a few rounds as deep as you want a single stripe to be.... then unravel that work and measure how long a color section needs to be to make a substantial stripe. Then decide how many colors of stripes you want and multiply that by your yards to stripe measurement.
I once measured out some Sassy stripes yarn (storebought) and the repeat pattern on that yarn stretched from one end of my house and back- no kidding I wound it off my front door knob to my back doorknob. It's actually kind of funny how that distance worked out.... but their repeat is very complicated- I doubt you intended to do one like that.
Anyway- I'd measure out a very big looped hank on some kitchen chairs on other sides of the room and then divide it into sections for where the dye would go. The number of strands you'd have is the number of times your stripe pattern will repeat in that ball.
A last tip- if you are making soaker pants- you may want to try to "fool your friends" by winding up two different loops for dying- one with smaller dimensions for the leg stripes- and one larger version for the butt stripes- that way your pants will have even stripes everywhere!