pHun with pH

After the weekend I spent recently in the UK doing plant dyeing with friends there, I came home with a fistful of pH strip packages and a lot of curiosity about what my dye baths would do if I made half of a bath acidic and the other half alkaline. Back in the winter I did a lot of dyeing with avocado stones and skins using a cold ammonia bath left to ferment for a couple of weeks. I thought I had answered all my questions about the possibilities of avocado waste because no matter what I did with the skins, stones, and mixtures of the two, I got basically the same range of colors from pale apricot through pinkish browns. Then Liz brought this magic dye bath with her to our weekend retreat, made of stones she had hammered into shards and cooked to a muddy pink-brown, and it produced the pale orange of fable that I’d read of and never achieved. If she could get that orange by boiling the stones, maybe I could boil the skins the same way and get the pink-red I’d read was a possibility. I walked over to the organic supermarket in my neighborhood where they have a salad bar, and asked them to save avocado skins and stones for me. The next day I was lugging home three and a half pounds of them.

The usual proportion of plant material to yarn to be dyed is 1:1, but I had a lot of skins to play with, so I weighed out about a pound of them and mordanted four ounces of wool superwash yarn. I put the skins into a pot with just enough water to cover them, in hopes of getting a very potent dye, and let the bath come to a boil. The boiling was probably a mistake. It is likely to have affected the color I got from my dye material, which started off as a discouraging green-brown. After two hours of cooking, a pound and a half of skins, 2.5 liters of water, it still wasn’t looking promising. I put a mordanted bit of yarn into the bath and it came out a faint murky greenish-brownish. I pondered whether something better might happen if I played with the pH, which was then at 5. Go alkaline? My previous baths were fermented in ammonia, which is alkaline. I hunted in my cupboard for something that would function as an alkaline modifier and found some bicarbonate of soda. I put a bit of my bath into a cup and added enough baking soda to raise the pH to 8, which changed the color from murky mud to dark wine red with a slightly viscous consistency. The bit of test yarn started taking on a bit of red-brown color, and I went to bed leaving the test yarn in the pH-modified bath.

Extracting dye from avocado skins with alkaline modifier

When I got up the next morning, I was pleased to see that the little length of yarn in my pH-modified bath sample had turned a dark russet red, quite a nice color, after sitting in the cold bath for the 12 or so hours. After putting half of my avocado skin bath aside, and leaving about 1 and a quarter liters of bath to work with, I put a mordanted hank into the bath with the skins and let it heat slowly without modifiers. After about 20 minutes of slow heating, the yarn was turning a pale shade of muddy beige, so I added a tablespoon and a half of baking soda, without any visible change to the bath, then another tablespoon and a half, which produced some bubbling in the brew. This raised the pH to 8, which was the goal. After about 15 minutes in the modified bath at a sub-boiling heat that was too hot to leave my finger in, the color of the yarn turned to khaki green. I let it continue to cook for maybe an hour, but the yarn color seemed stuck at khaki, so I added another tablespoon and a half of baking soda to raise the pH to 9. I turned off the heat and let the yarn sit in the hot but cooling bath for several more hours, then rinsed it for a color check. It was a russet red-brown with a little bit of red/pink variegation. I threw it back into the dye in hopes of getting more of the red/pink.

It’s good not to get too attached to your hopes when you’re doing plant dyeing! After a couple of hours, I started to get somewhere with my avocado skin dye, but it wasn’t the pink/red I was hoping for. Instead I got a very nice dark brown rust color. I expected it to lighten a lot when it dried, so I kept it in hot dye bath. And then I forgot to turn off the stove. The bath cooked for an extra couple of hours until the skins almost completely dissolved into nothingness. It produced a very weird smell in the house and the dye was the color and viscosity of congealed blood. But I got the most amazing hank! Dark, dark, dark maroon! Actually a dark red brown. The yarn itself may have suffered in the chemical processes because it seems less soft and pliable than it used to be, but I love the color so much that I’ll take a bit of brittleness in the yarn’s texture. The exhaust bath produced a strong pinkish brown along the lines of my earlier dyeings with avocado skins and pits fermented in ammonia, but slightly pinker.

Alkaline-modified avocado skin dye, first dyeing and exhaust bath

I still had about half of my unmodified avocado skin bath in a container sitting in the refrigerator, and about three-quarters of a pound of unused avocado skins. I cooked the skins in the remaining bath for a lot of hours and got the same depressing mud brown I got with the earlier bath, despite the heavy concentration of plant material, so I decided to see what would happen if I modified this batch in the acidic direction, which was at pH 5 before modification. I added tablespoon after tablespoon of lemon juice to the bath, but it was stuck at 4 for a long time before I finally added enough lemon juice to get it down to 3. The bath turned pinkish-orange, but once again the yarn was another rust brown, this time with a more orange cast. Very pretty, but I wasn’t going to get that red-pink unicorn. Eventually it turned the auburn of a redhead’s hair. It was a little redundant with the palette I already had in my plant dyeings, but it was a pleasing color.

Liz, my English dyeing buddy, has been doing some further experiments with avocado stone dye. She speculates that facts that are true of dyeing with madder might also apply to dyeing with avocado: “With madder, different dye elements become active as the temperature increases; orange at 50-60 degrees, red at 60-70, and brown over 70. To reduce the brown element you can add a cloth bag with wheat bran which absorbs the brown pigments, so maybe this would work with avocado.” That means I have to go on a serious hunt for my cooking thermometer, which I haven’t seen in years. I wonder if the battery is even still alive? In any case, I must avoid bubbles during the heating process, and cut the heat before it gets beyond wafts of steam. And bran. Must hunt up some wheat bran, next time I dye with avocado stones. My preferred yarn base, undyed Wollmeise lace, might also be a factor in the pink-browns I get. Liz got a range of pastel pinks and oranges using Spindrift, a non-superwash Shetland wool yarn, and pink-browns that are similar to my results using a superwash blue-faced Leicester wool yarn that is a lot like Wollmeise.

I also wanted to have another go at black bean dye, after having gotten wonderful results the last time I had dyed with it. I was hoping to get a nice clear blue that I could then dip into some green marigold bath I had frozen for a future time, in hopes of getting an aqua. Unfortunately this current batch of beans just wasn’t as dye-filled as the previous batch. Instead of clear blue I got a blue-gray that wasn’t going to turn into aqua, so I lowered the pH from the original 5 of the unmodified bath and added lemon until it got down to 3. I ended up with a gray lavender that was a half-shade more violet than my other gray lavenders. There isn’t a lot of difference between it and three or four similar cakes of yarn I’ve dyed with black bean and lemon, but it’s good for constructing gradients.

I had divided that black bean bath into two containers, and still had half of the bath to play with. Something I’d read indicated that alkaline might turn the bath green, and I had hopes that I might get a kind of aqua if I could luck into the perfect amount of alkaline modifier that caught the color just as it was turning green. I started off by adding a cautious two teaspoons of washing soda to my black bean bath, and I got quite an instantaneous change. The bath turned very dark green in seconds, along with bubbling and a change in viscosity. Within a minute, my yarn turned a very pretty mint green. Oh well, not aqua. I decided to leave the yarn in the bath and let it deepen a bit.

Here’s a photo. The yarn had been in the green bath for less than a minute when I took the picture.

Black bean dye bath pH modified with lemon and washing soda
Black bean dye bath, pH modified with lemon, top, and washing soda, bottom

Interestingly, while the washing soda had a strong effect on the black bean bath, almost none of the color affixed to the yarn. I got a barely-there green tint. They do call it washing soda for a reason, but there are plant dyes for which it is quite a potent modifier and fibers to which the pigment will affix. But not this time. I saved the hank in order to re-dye it in some different dyeing experiment.

Black bean dyed hanks, acidic and alkaline modifiers, avocado skin dyed hank, acidic modifier
On left, washing soda modifier drained the color from the hank. Center, black bean hank modified with lemon; right, avocado skin hank modified with lemon

I had some still-wet mordanted hanks that were in danger of moldering in their plastic bags if I didn’t dye with them soon, so I started thinking about having black rice with baked tofu and sweet potatoes and baked tofu for dinner. Of course my real goal was to see what would happen in pH experiment with black rice dye. I decided to soak the rice in cold water instead of just cooking it as I did last time I dyed with it, to see if a cold soak would get me a different color than cooking it did. Maybe a clearer blue, instead of the gray-blue I got before. It immediately started releasing color in the cold water, and after a couple of hours, well before it was time to start cooking the black rice for dinner, I had a very dark and potent-looking dye bath. I cut off a couple of inches from the pale greenish-yellow hank, which I had also dipped in my green marigold exhaust bath in disappointed hopes of getting a nicer light green, and dipped an end of it in the cold black rice bath. After about a half hour, it came out aqua!

test sample of yarn overdyed in black rice bath
Black bean bath with alkaline modifier, overdyed in marigold, then overdyed in a cold soak black rice bath

I let the black rice sit in the cold bath for another couple of hours before draining it off and adding more water to the rice for cooking, with extra for another bath derived from the cooked rice. While dinner and the additional dye bath were cooking, I threw the entire black bean/marigold/washing soda hank into the unmodified cold black rice bath with a reasonable expectation that I’d finally get my aqua. At first it was a scary gray, but it washed out to a gray-toned teal. I may have missed my moment with the aqua by letting the black rice soak longer in hopes of getting a more potent bath. In dyeing as well as everything else, timing is everything. Nevertheless the gray-toned teal was a good color on its own merits.

Modifying black bean dye with lemon
Top, black bean dye modified with lemon, wrapped around similarly colored yarn. Bottom, teal hank after many overdyes and pH experiments

Some days later, after my daughter hunted around our refrigerator for food that might please our little granddaughter and found only containers of dye bath, I felt a guilt-tripped motivation to use one of those inedible potions clogging the refrigerator. I divided the cooked black rice bath into two for the pH experiments, adding white vinegar to bring one of the baths to pH 3 and baking soda to the other bath to bring it to pH 9. I failed to note the original pH of the bath, but was somewhere in the middle, 5 or 6. The acidic bath changed color from black-purple to a brown-tinged pink-red while the alkaline turned dark teal and somewhat viscous. a hank each went into the baths at room temperature and stayed there for most of the next 24 hours.

I was able to end this series of dye experiments with very gratifying results: from the acidic bath, a true violet for the first time, rather than pale grayish lavenders attained from black beans with lemon modifiers, and a teal-tinged blue that looks exactly like denim from the alkaline bath.

Black rice hank modified with white vinegar, same dye bath modified with baking soda
Finally, a true violet! Also a great faded denim variegation, all thanks to the magic of pH modifiers, white vinegar and baking soda!

I asked the wise ones on my Ravelry group, “Do you have any insight into the chemistry that would make the alkaline-modified dye wash out of a black bean dyeing when I used washing soda while the colors stayed in a baking soda-modified black rice dye?” Candy gave me the following answer:

The strength of the modifier?? Washing soda is Na2CO3 and baking soda is NaHCO3. One looks like a sort of bifurcated antennae and the other looks like a very balanced equilateral triangle. Now, that is a simplified description, but for any chemical reactions the shape of the molecules can affect strength of action AND what the action is.

Okay, so, the reason for mordanting and modifying is to open the shaft of the fiber to all the dyestuff to enter and kind of sticky itself in the little scales on the shaft. IF the mordant opens the fiber and the modifier closes it, changes it, OR likely more importantly here, changes the electrical charge, the effect is different.

Baking soda, the one that looks like the antennae, had the elongated shape AND only 1 positive leaning end. It may, for your purposes, be allowing much more of the dyestuff to stick into the scales since not as much is pulled onto or stuck to the modifier when it is washed out.

Washing soda is the triangular one AND it has 2 positive charges equally spaced at one end but that end is still, relatively speaking, close to the opposite side. It makes the charge stronger, which may, in turn, pull or hold on to more of the dyestuff than it allows to deposit.

Acid modifiers pull at the charges on the dyestuff, which is what gives the color shift. Often, the color changes are oppositional, which means kind of like red tones to greenish tones, yellow tones to more purplish tones. It is not perfect, it is affected by the strength of the modifiers and it is all I can think of.

I also may be totally wrong. The best assessments can sometimes be on the wrong track in any more scientific explanation, but there is a reason that you modify the dyes with either acids or bases and common sense chemically would lead someone to point to the charges and how well those substances can affect the charge of the dye.

Knowing that people who actually understand basic chemistry are going to wince at the way I’m explaining the chemical processes to myself,  it seems that washing soda is too strong a modifier to allow the black bean dye to stick to my mordanted superwash wool. But washing soda worked well with rhubarb leaf dye. Candy explained that that was because of the oxalic acid that makes rhubarb leaves toxic. If I’m understanding correctly, the intensity of the oxalic acid in the rhubarb leaves combined with the intensity of the alkaline in the washing soda generated a charge that affixed the dye color to the yarn. Whereas the wishy-washy acid-ish tendency of the black bean didn’t produce a strong enough charge with the washing soda to enable the color to affix to the yarn.

I’ll close this post with some pictures of my new colors in action, lest anyone think that all I ever do with my yarn is dye it!

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8 thoughts on “pHun with pH

  1. I found you through a German knitter on Ravelry, just the other day…yesterday I think. And I’ve been happily whiling away an hour or so here on your blog. I’ve just started dipping my inquisitive toes into the dyeing world, so I’ve been fascinated to read your accounts of natural plant dyeing. I have already learned so much from you, and been inspired by you…so thank you!

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