I've been asked a number of times how I dye the variegated thread. It's very simple! This has become my favorite thread to stitch with in either variegated or solids. It ends up with a smooth finish and nice sheen.
I use standard, mercerized cotton crochet thread.
Then tie each end with a loose wire. If you make it too tight, you'll end up with white spots there:
Soak the thread in soda ash solution about 20 mins. Wring out extra liquid and it's ready to dye in Procion dyes. I first dip the middle third in one color. (Sorry no dye in the pot, but you can imagine it.)
Then I dip each of the ends in a different color. You can see the three colors on this ribbon I dyed using the same method:
As with any dyeing, I put the thread in a plastic container, let it sit overnight, then rinse out excess dye.