Getting the yellow out

Getting the yellow out; the yellow liquid that is not permanent goes through the cloth which is being used like a filter, but the blue woad pigment, which is a solid, gets captured in the cloth.

I harvested more than on June 19, but I used about the same amount of water when I processed it. This led to a super-concentrated batch, which of course led to new discoveries. More on that later in the post.

Dipping the scarf in the woad after adding alkali but before introducing oxygen, which turns it from a dye to a (solid) pigment.

I decided after adding the wood ash (to bring the PH up to 10) but before pouring it back and forth between the buckets (to oxygenate) to dye a bamboo rayon scarf. As is usual with both woad and indigo, when the vat is reduced (low oxygen) it’s a deep green, and so is the fabric when you first pull it out. But then when exposed to air (oxygen) it turns a true blue. In the case of fresh woad leaves like I was using, there is a significant amount of fugitive yellow in the leaves; and when I dyed the scarf, I had done nothing to get rid of that yellow. In any case-the scarf ended up a really lovely blue; so lovely it’s tempting to just keep it as is. But of course I’m curious about what if…I’ll get to that later. But now onto getting rid of the fugitive yellow. ​

At left, the color of the infusion after removing the leaves. At right, the same liquid after adding the alkali and exposing it to oxygen (by pouring it back and forth from one bucket to another.)

After dyeing the scarf, I did the pouring back and forth to oxygenate the infusion of woad leaves (I had already taken the leaves out, it’s like making tea.) Woad and indigo are actually pigments, that is, a solid; dye penetrates fiber, indigo and woad coat the fiber. When I used a higher water-to-woad ratio to make the “tea,” (see my last post) the heavier, solid pigment sank to the bottom, and the yellow liquid could be scooped or siphoned off the top. But this batch was SO PIGMENT HEAVY that the pigment didn’t settle at all-even after sitting overnight! ​

I just went ahead and tried to strain it; normally, again, the yellow goes through the cloth and the blue pigment gets trapped on top of the filter cloth. But the  “waste” water after I strained the liquid (first photo at the top of this post) was not yellow-it was  really  dark. Obviously there was a lot of pigment left, so I strained the “waste” water a second time. Sure enough, this second straining captured plenty more pigment on top of the cloth. Doing a more concentrated batch seems to be a great way to avoid lifting larger, heavier buckets! However, it means that the pigment won’t settle, and has to be strained at least twice. 

 I’m kicking myself for not also dyeing a fabric swatch in addition to the scarf. That way I could cut the swatch in pieces, and try different stuff with the pieces to make comparisons. I wonder if next time I process woad, I gave the scarf an additional dip, if that would make the color deeper? I have this strange suspicion it wouldn’t do much! My reasoning is that there was SO MUCH pigment in that water, it was so concentrated, that the reason it didn’t go darker is chemical, not WOF (weight of fiber) to woad pigment ratio. So the second thing I want to do, is take some of the purified pigment, and reduce it again to make a dye vat, and then re-dye the scarf. My prediction is that without all the fugitive yellow still mixed in, the color of the fabric will go way deeper. Now I have to do another batch of woad, and put my theories to the test.

One last observation, woad is definitely a cut-and-come-again plant. The woad out at the NCC East 40 is happy that I’ve been persistently pulling the weeds to give it more room. Today-one day after I harvested the woad I’m showing in this post-you can’t even tell that I just harvested yesterday!