Oak Gall and Oak Bark Dye on Wool at Acid and Alkali pH

"Ye Gods and little fishes, is there no end to your boring brown bark dyes?" 
I cowered at the fearsome glare of my companion, Elinor Gotland. 
"Well, I did think the yarn might come out more pink."
"Pink? Whoever told you oak would dye wool pink?"
I shifted uneasily in my chair.
"Actually, I said that myself. I know I got pinky brown colours from oak galls and from oak twigs and again from acorns when I dyed with them before. Seems I've been a mine of misinformation about oak as a dye and a tannin mordant."
Elinor put down her oak twig.
"Wash down the humble pie with some other brown tannins, Beaut. You've left your tea bag brewing long enough to strip paint."

This past couple of months, I've been much interested by the way a week of fermentation in cold water makes bark dyes acidic. Simmering yarn and fabric in a fermented bark dye bath has given pale colours, increasing the pH with soda ash has not only deepened the colour, but in the case of silver birch, transformed it from beige to pink. All done with no need to mordant wool or cotton in advance.

Hoping to explore a little more of this alchemy, I went looking for fallen oak branches. Although there were heaps of fresh twigs under the trees in autumn, in March I found only crumbly old wood and one small branch to peel. On the leafless trees, dried up oak galls were easy to spot and no trouble to pull off.

Coming home with a 200g haul, mostly oak galls and a handful of peeled oak bark, I broke the galls up with a hammer and left the lot to soak in a bucket of water for a week or so. After simmering it in a pot for an hour, I sieved the bits out of the dye bath through a piece of old net curtain. 

Three 50g skeins of unmordanted wool yarn were simmered for an hour. Having tested the dye bath to check it was the expected acidic pH 5, I wasn't surprised that the wool went beige. Taking out one skein, I added dissolved soda ash to bring the dye bath up to neutral pH 7 and simmered it again before taking out another skein. Which had gone brown.

Deciding to bash on anyway, I increased the dye bath to alkaline pH 9 and gave the last skein a final simmer. It came out a dimmer, duller brown.  Here are samples of the dye bath at each pH. The more alkaline, the blacker the bath got, but never a hint of pink in the wool it dyed.

Wool Dyed with Oak Bark and Oak Galls at pH 5, pH 7 and pH 9

The yarn was left to cure for a week then each skein was rinsed separately and allowed to dry again before I brought all three outdoors to examine them in natural light, drink tea and have my work critiqued by my dear companion. 

"Did you save those bashed up oak galls, Beaut? There'll still be plenty of tannin in them."
"Yes, they're in that bucket of water. Don't think I'll use them to dye anything else, but I might try mordanting some cotton."
"Don't go getting that wrong, like before. You'll need to mordant the cotton with alum as well, then put it back in the tannin bath."
"I know, I know. Hardly seems worth the bother, when a single bath in a 5% solution of aluminium acetate will mordant cotton and linen perfectly well."
Elinor treated me to another of her looks.
"That's not a very enterprising attitude. I thought you were going to grow your own ecofriendly soy beans this year and try mordanting with them."
"Soy milk isn't a mordant, it's a protein binding agent. And no, I'm not planting soy in my garden."
"Just going let someone else chop down a rainforest and replant it with a genetically modified soy monoculture?"
"Just going to ignore the whole soy option, Elinor." 
"I had a friend who swore by soy milk for ecoprinting cotton."
"Yeah, and I've got a friend who's going swimming in a bucket of oak galls in a minute." 
Exit Elinor, pursued by a bear. A brown one.