I've just skeined this up, and I thought I'd share - it's for a non-craftster swap (but, yeah, Harry Potter) so hopefully my partner won't see it here. I'm using Knit Picks bare fingerweight yarn and lanaset dyes. And before you say it's not the right green for Slytherin, it's not, but I think it's the right one in the project. A darker green would have been shocking, I think, with all that yellow/gold/bronze, red, and black.
Alright, here's the deal about self-striping sock yarn. There's some disagreement as to how long it has to be, but I got my numbers from Vildhavre's tutorial
https://www.craftster.org/forum/index.php?topic=188946.0, because god knows I only knit as a last resort.
What I had heard previously is that you need a loop of at least 25 feet (or 50 feet?), but was unable to find confirmation of that. So, convinced by her pictures, I went with Vildhavre's numbers, which is roughly 30 yards. And not wanting to tie up the chairs (ha ha), I staked it out in the garden. (Actually, this approach also means the dyeing can be more flexible in regards to number and size of stripes.)

One side is really a stake, the other is a fence post.

I am walking along inside the loop to be sure I don't mess it up. It needs to be a big open loop. As you'll see.
Once all the yarn is in the big loop (it's about 12 passes), every thing is tied, and I made ties every two or three yards. And the more ties the better, people! I'm terrified of tangles. Then I freed one end, and began to make interior loops of about two arm-lengths each, which are tied off themselves.

Then they are soaked overnight and then put into jars with vinegar and dye, and heated in a pan of water for half an hour or so... covered, to keep the steam in.

Fewer colors can be done in a pot with a lid; with eight colors, I was forced to use this roasting pan with foil on top. Otherwise- completely the same. (Although, last time, I filled the jars to overflowing and spaces between the colors filled itself in, and this time, I didn't, and they didn't... so, I suppose there's a lesson in that.)
Let it cool, rinse it out (several times)... let it dry. And then you see how well you tied it. Then it's back on the stakes to be untied.

And then niddy-noddied.
And then twisted up into a skein.

And the other thing is that I'm doing some just in Ravenclaw colors. It's two colors, so, a much shorter loop.

And it was dyed in a pot with roving and other yarn, but otherwise just like the jars, but on a bigger scale.

And here that is skeined:

It's fun, despite all the winding and unwinding, I'm already planning lots of non-Harry Potter related colorways.
