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Dyeing with rhubarb

September 9, 2014

My third experiment with natural dyeing involved rhubarb. I was hoping that rhubarb root would give me a red dye. I planted a rhubarb three years ago and the bush is now large enough to split into another plant. However, I decided to utilize the roots for a little dye experiment. I dug up the roots, chopped them up and soaked them for five days in a glass jar with about 3/4 of a gallon of tap water and maybe a cup of common household ammonia. Almost immediately the water-ammonia mix became a bright, clear red–very promising. To keep the color from eroding in direct sunlight, I stored the jar in a shaded part of one of our porches.

Rhubarb root drying in my sink after being scrubbed of all dirt in warm water.

I chopped the root up. If you look closely, you’ll notice a shadowy pink ring around the center of the root. This is the dye.


Day two of steeping the roots in a mixture of ammonia and tap water.



I would’ve let the dye liquor sit a few days longer, but I was preparing to leave for an open-ended trip, so I decided to just go for it. I dyed a skein of local 100% alpaca yarn–the same brand, same off-white color as was used in previous dye experiments plus a skein of pearl-white yarn comprised of yak down and silk.


Two skeins of alpaca yarn on the top and one skein of yak-silk yarn on the bottom.

I pre-mordanted both yarns in the same mix of alum and cream of tartar, but I only simmered them for about 20 minutes. At the same time, I added my rhubarb dye liquor to a pot I claimed for dyeing filled with maybe 1/2 a gallon of tap water that I simmered. I then drained, but did not rinse, the yarns then immediately added them to the simmering dye bath and left them in the bath for about 45 minutes, still simmering. I stirred the yarn periodically, but I left both skeins tied.


 Plopping pre-mordanted (barely) yarn into the simmering bath.



During the whole time the yarn was simmering, there didn’t seem to be much intake of dye into either skein of yarn. Finally, after 45 minutes, the dye bath looked a little brownish and I decided that I’d gotten all the color from it that I was going to and I removed the yarn. I soaked both skeins together in lukewarm rice vinegar for maybe 20 minutes, then rinsed them in cool tap water (cool because I forgot about the effect of temperature shock on animal fiber).


Soaking in some very old brown rice vinegar. 

As you can see above, the color I got was, well, subtle. Definitely not red. It was, however, rinse-fast as far as I could tell. I hung the yarn to dry overnight.


The roots and yarn all mixed up together after draining off the dye water. The roots are still quite red, but I didn’t have time to set up another bottle to see if I could extract more dye. Next time.



Below’s a picture of both skeins the next day, after they had dried. The alpaca was darker and also very uniform in color. In fact, it’s a much pinker hue than the picture shows–a color that makes me think of a pencil eraser. The yak-silk yarn was more tightly tied up in the skein. It also seemed not to really rise at all during the simmering, which I believe resulted in a very uneven dye up-take that, frankly, was really the only redeeming thing about the results of this dye bath. The pinkish hue of the alpaca has grown on me, but I really do like the subtle marbling of the yak. In addition to being paler than the alpaca, the yak is also a golden tan–no hints of red or orange at all. Below is a picture of the super-soft scarf I’m crocheting with it. The color of the yarn is actually quite a bit darker and the marbling more noticeable in real life.


Alpaca in the background, yak-silk in the foreground.



Analysis: Originally I assumed the experiment was another partial failure, along the lines of my calendula solar bath. I was hoping for a deep, ruddy color but got pale browns. However, A Verb for Keeping Warm, a store in Oakland, sells packets of rhubarb root with a sample of wool yarn dyed with the product and the color was much the same as my alpaca yarn. So.

I’m not sure why the yak-silk blend turned out so pale. Things I do know that I could’ve better controlled include (1) the pre-mordant process (next time, simmer for 1-2 hours, and let the yarn cool overnight in the mordant bath), (2) use bottled water (I’m ready to start getting more scientific about this, the first step of which is controlling for ph. I’ve acquired some ph test strips to do this, but unless I’m using a recipe that specifies ph, I think the first step is to go for neutral water and proceed from there. Another reason to use rain or filtered water is minimizing the chance of any minerals that might also influence the outcome of a dye bath), (3) aim for more precise temperature control and also prolong exposure to the dyeing element for as long as possible. I’ll also invest in a bottle of good ol’ synthetic vinegar, the kind used for cleaning. As far as mordants go, I’m sticking to vinegar and alum, for now, I think. I did keep and freeze all the leaves from harvesting the rhubarb root. They now reside in a ziplock bag in our deep freeze that is clearly labeled as “poison-oxalic acid”. From what I’ve read, rhubarb leaves are a traditional mordant and even dye in the Tibetan rug industry. However, a botanist friend tells me that oxalic acid that comes into contact with the mouth may cause one’s throat to seal up, so… Definitely serious stuff. From what I’ve read, it seems like oxalic acid probably doesn’t do anything other than improve the fastness of dyes, which isn’t a big concern of mine right now, as I’m still working on being able to generate colors. I think step one of this learning process is just figuring out a method of operation, followed by learning what kinds of natural materials can generate what kinds of color, followed by developing some sort of predictability to the whole thing so that I can at least attempt to replicate colors. Fastness is low on the list for me. First I need to learn how to make the kinds of colors that I really care enough about to want to keep them on my fabric for awhile. I’ll hold onto the rhubarb leaves, for now.


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