Susan's Mason Jar Dying Method
I've tried dyeing with Kool-Aid (in the microwave); there are lots of directions on the Internet. Unfortunately, the colours are rather limited (though I did manage to create a really terrifying bright yellow green with a package each of Kiwi Lime and Lemon Lime. (it's the colour that Oscar the Grouch would be if he had a really good bath). They're great colours for kids, though. A friend is making the swirly tube socks with Kool-Aid yarn that her daughter helped dye.
Then I found that the Art College supply store carries Cushing acid dyes, which come in a range of colours. I bought some, but was reluctant to use it in my kitchen until I read (I think on the Kimono Jacket list) about dyeing the yarn in mason jars.
I wound off the yarn into 1-oz skeins, and since it's a very oily unscoured wool, I soaked it overnight with a rather nasty chemical called Synthrapol (gloves needed). Hot water (maybe with a little detergent) would be fine with a more processed yarn, I think. I measured a package of dye, which is good for 1 lb of wool. There are 2 tsp in the package, so for 1 oz I used 1/8 of a tsp in a 1 quart jar, I added boiling water to half fill the jar and 1/2 cup of vinegar to set the dye. I put in the wool, mixed it in a little and topped up the jars, mixed a bit more, and put lids on the jar. Then I put the jars in a canning kettle and heated it, just off the boil for about an hour--until all the dye was exhausted. I let the yarn cool a bit, then rinsed it thoroughly in water that matched the heat of the liquid in the jars, and hung it to dye.
The first skein I did (blue) was still knotted, so I got a tie-dye effect. I wanted a solid, so I later redyed it and the colour is quite even. The violet yarn came out mottled--I think because at that point I wasn't using boiling water to mix the dye. The redgrape and apricot came out very well. The colours are quite close to the picture in the book, though judging from my Wildfoote sample card not to the actual yarns.
The main point of this method is to dye small amounts of yarn for colour work. I imagine it would be difficult to dye a lot of yarn the same colour with this method. You could probably fit another 1/2 oz of yarn in the jar and still be able to mix the dye in. The other thing would be to mix up enough dye for the total amount of yarn (say 1 tsp for 8 oz) in an easily divided quantity (2 cups) and divide it as precisely as possible among the jars (1/4 cup each), then add more water and the vinegar and proceed.
I have a cone of the wool/cotton/nylon from Elann, and since I don't really want four or five pairs of identical socks, I'll probably try dyeing some of that. The cotton should make it interesting, though Cushing makes a dye for cellulose fibres. I'll let you know what happens.