For the Divination class in the Harry Potter Knit and Crochet House Cup this month, I am dyeing some roving with coffee, then spinning and knitting it. This is how I dyed it.
I started with about 3.5 oz. of plain wool roving. I don't know what breed it is. It's some stuff I forgot I had.
I made 3 pots of very strong coffee with about 1/4 vinegar mixed in the water. I used some nasty Folgers decaf that I wouldn't ever drink.
I poured the coffee in my crockpot. This is my dyeing crockpot, but because coffee is drinkable (well maybe not the Folgers decaf) you could use your normal crockpot. I left the coffee to cool for a couple hours (in order to be close to room temperature).
Then, I carefully added the roving into the pot, pushing it down unitl everything was covered. I could have soaked the roving beforehand to insure a more even dye job, but I like my roving/yarn to be kinda blotchy.
I cooked the roving on high for about 4 hours, occasionally checking to see if I liked the color and poking it down into the coffee more. I was very surprised that the color in the coffee didin't exhaust the way dye does
Then, I carefully pulled it out (with my fingers and a wooden spoon) and set it in the bowl to cool.
After it was cool, I filled the sink with room temperature water, carefully put the roving in and squished it around. As you can see, the water turned brown. So, I removed the roving, drained the sink and filled it again. This time the water was clear.
Then, I took the roving out of the sink and carfully squezed (not wrung) it out. Then, I wrapped it in an old bath towel like a roving burrito and walked on it to squeeze mor water out. After that, the roving burrito went in the washing machine on the spin cycle (make sure that it is firmly wrapped in the towel and that the washer is set past the final rinse cycle) The roving is now hanging to dry in my laundry room and should be read to spin in day or two.
If you decide to try this, remember to be nice to your wool or else you will have felt. This means no sudden temperature changes, no boiling the dye water, no agitating the wet wool and no pouring water on top of the wool. Enjoy.