A question on Ravelry about dyeing yarn spun in the grease reminded me of how much fun it is to rainbow dye grease fleece. Rainbow dyeing breaks the rules about dyeing--you use unscoured fleece, raw dye powder, a minimum of hot water; then you leave the fleece, water, dyes and heat to do their work. Rainbow dyeing requires using more dyestuff and more mordant. (That is, if vinegar is your mordant; natural dyeing works a bit differently.) It's not an efficient production method and you can't duplicate results, but you can get interesting results from playing with the colours.
I use a very precise, scientific approach to this type of dyeing: I grabbed handfuls of raw, white Romney fleece (from Meagan Linklater), my dye pot, and my Greener Shades acid dyes. I filled the pot about one third full of hot, hot tap water to which I added several glugs of white vinegar and a squirt of Sunlight dish washing soap. I then stuffed the raw fleece into the solution, and sprinkled a bit of dye powder on the fleece, poking the wool into the water, but not stirring or mixing the dyes. (I used River Blue, Flame Red and Sunshine Yellow.) The colours in the pot should be quite intense, if you want bright colours. Areas with heavy grease will not take up dye as well as drier sections and your colours will be paler than if you had started with scoured fleece (which, of course, you may prefer to do). I don't use fleece with a heavy lanolin content (such as Merino) because it takes too much dye to get reasonable results.
The usual dye safety rules apply: your pots and other equipment should be used for dyeing only; wear rubber gloves and a mask, especially when working with powdered dyes. If you can do so, dye outdoors or in a properly ventilated area. Your kitchen isn't the best place to be dyeing (unless you're using powdered drink mixes), but if you kitchen dye, put away all food and kitchen equipment, cover your work area with plastic or newspaper and clean up thoroughly when you're done. Keep the stove fan on when your pot is simmering. Small and medium sized children and pets do not belong around dye pots. (Morris notwithstanding; I chased him away after the photo below and, no, he did not manage to stick his beak into the pot.)
Morris is very helpful, especially when it comes to inspecting raw fleece:
This is the first layer:
I then layered the remaining fleece over the first, again, just gently poking the fleece into the water. I poured about 250 ml. of hot, soapy water over this final layer:
The covered pot is now sitting in full sunlight atop out barbeque. Temperatures are expected to rise above the 30C mark today; with these dyes, that may be all the heat required to set the colours. If not, I'll bring the pot up to a gentle simmer for about 30 minutes and then allow the bath to cool. When the water is clear, I'll rinse the fibres, either later today or tomorrow morning.
The most important things to remember when rainbow dyeing are to use just enough water to barely cover the fibres and to not stir the dye pot, no matter how much you are tempted! Stirring things up will mix the dyes and your resulting colours will be muddy. If you don't like what you get, you can over dye any or all of the fleece, but, for now, leave things alone.