Yesterday's overdyeing experiment has left me with some very pretty cashmere yarn, in colors much better suited to fall knitting than what I started out with.
The turquoise blue yarn is now a soft brown-green.
That one might not seem as intuitive as it is. Overdyeing blue yarns with brown always give me a pretty patina effect, so I was expecting it. It's a good solution for yarn that is too-blue.
I took the pink yarn one step further. The blue-gray was pretty. But I decided to add an additional step, and mixed a red for use on half of the skeins (using the same base red to mix my brown for the yarn above, so they would compliment each other) to overdye the gray. Because acid dyes adhere using a molecular bond, you can't overdye indefinitely, but three baths - the original pale pink, the gray, and finally the red, is well within what works for me. The gray and red play nicely together.
Overdyeing is a nice solution to yarn you love that needs a change in color. I'm undecided on whether to stripe these skeins into something soft and lovely to wear around my neck -- they all coordinate nicely, or whether to turn them into hats and mittens and other small items. But having use the over dye process to give them a bit of a color change, I know I'll be using them soon.