First I soak black turtle beans in water over night. I use about twice as much water as black beans, and stir ever so often as I walk by. Then I scoop the now dark purple water off the beans and into a bucket to dye in. (The beans made delicious burgers).
And here is the scarf after spending the night in the cool black bean dye. Very pretty magenta, but not the blue that I'm looking for. To correct this I have to adjust the PH back to the other side by soaking it for a few minutes in a water and baking soda solution. Its pretty amazing to watch actually, as the color changes right before my eyes. Here it is after just a few seconds in the baking soda wash.
The final color is this beautiful steel blue.