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).
I added a splash of vinegar to the dye bath, since silk as a protein fiber tends to take up color better in a slightly acidic bath. This also has the effect of turning my dye a brighter, magenta purple.
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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.