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Friday, 11 May 2018

A Trial of Birch Leaf Dye

My companion, Elinor Gotland, watched me empty out a pocket stuffed with birch leaves.
"I suppose you'll be boiling that lot up and stinking out the kitchen again."
"Simmering, Elinor, not boiling. I've no idea if birch leaf dye will smell, the books never say anything about that. And yes, the dog and I had a lovely woodland walk, thanks for asking."
"Mmmm, no sooner have the trees sprouted a few leaves than you go pulling them all off."
"I only stripped a twig from each silver birch I passed. Just going to check how much I've got."
"Oh, you're not weighing those leaves in the kitchen scales, are you? They might be covered in bird poo or anything."
"Oh hush, I'll give the dish a wash. Smile, why don't you, this is the beginning of an exciting new dye experiment."
"Not if you're a birch tree, it's not."


My fresh birch leaves weighed just over 100g. Ignoring Elinor's grouchy temper, I added water to the pot, simmered them for an hour and left them to cool. Jenny Dean's book Wild Colour said birch leaves would dye an equal weight of fibre which had been mordanted in advance, so I planned to add 100g of premordanted wool.
Three 25g skeins of Shetland wool yarn were already prepared, on the left, one mordanted with 10% alum, in the middle, one mordanted with 2% iron and on the right, one mordanted with 2% copper solution.  To take another look at the difference between using iron and copper either as mordants or as modifiers after dyeing alum mordanted yarn, I wanted a fourth 25g skein, so I put another Shetland one in with some other wool yarn I happened to be mordanting in alum.
A sample of the birch leaf dye bath looked pale yellow and tested mildly acidic with pH paper. Adding a little soda ash to a second sample deepened the colour, but I thought this time, I would not meddle with the pH of the whole bath, just leave it as it was and concentrate on the effects of metal mordants and modifiers.
All four skeins went into the dye pot with the leaves still in it, together with a small piece of unmordanted cotton and a piece of linen mordanted with aluminium acetate. They were simmered for nearly an hour and left to soak overnight.
Taking them out next day, at first I thought I had got my labelling mixed up. According to my routine, a skein with iron mordant gets a yellow plastic clip, a copper one has a white clip and the two alum mordanted skeins should have pink clips. After a pause for staring at the wool and thinking about recent results with daffodil, dandelion and ivy leaf dye baths, I decided the brownest colour was typical of iron premordant and had been correctly tagged and the warmer toned skein was likely to be copper as shown by its white tag. Which left the two pink clipped skeins, the first two on the left of this photo, both alum, but not identical, one being a much deeper and more vibrant yellow green than the other. 
Elinor had hidden herself in a shady spot, where I hoped a long, cold drink might be improving her mood.
"You won't dry that wool by breathing all over it, Beaut. And it won't do the colour any good to hang it in direct sun, it'll fade.That sheep is paranoid too much sunshine will bleach her fleece and still inclined to grouch at me. "What's a May Bank Holiday for, if not getting sunburned? Or awfully dehydrated?" Elinor clinked her ice cubes and bit into her cucumber slice. 
"Half a minute now, I'm trying to think."
"Ah, is that why you've gone all red in the face?"
"This second alum mordanted skein - I may have made a mistake with my calculations."
"Again, Beaut? It's no surprise you were in the Remedial Maths class at school."
"I think I mordanted it with 20% alum instead of 10% by weight. I put it in to mordant with some skeins of aran yarn and I reckon I must have done the whole lot wrong."


Before completing the planned trial, I took the paler skein of alum mordanted yarn and divided it into parts. One part was saved just as it was, representing my usual 10% alum mordant. In this photo, it is the little drab shein on top of the larger one, which I think had a 20% alum mordant.

Birch Leaf Dye on Alum, Iron and Copper Mordanted or Modified Wool and Aluminium Acetate Mordanted Linen

A short length of the 10% alum mordanted yarn was soaked in alkali solution, just to get an idea of what alkalinising a whole dye bath might do. It turned a brighter yellow, though not as saturated a shade as the 20% alum mordanted yarn (left). Another part of the 10% alum yarn was simmered for five minutes with a splash of iron water to modify it, turning a grey green, whereas the iron premordanted skein was much browner (centre). The final part of the 10% alum mordanted yarn was simmered with a splash of copper solution, turning it a green gold, less gingery than the copper premordanted skein (right).

Birch leaf dye has proved well worth a trial and it does look as though adding soda ash to alkalinise the bath would bring up the colour even more. As before, the effect of modifying alum mordanted yarn with iron and copper pleases me better than the effect of actually mordanting the yarn with iron or copper beforehand. After my probable miscalculation, it seems to me I should consider using a higher percentage of alum to mordant wool in future. The older dye books often specify using more mordant than modern authors recommend, could be the old girls knew more than they have been credited with. Hey ho, I already have some skeins which I think were accidentally mordanted at 20% by weight, they were Drops Alaska on sale at cut price from Wool Warehouse, so it won't cost a bomb to buy some more and do a few more experiments. And there are masses of birch leaves and far more to come.

6 comments:

  1. oddly enough my birch leaves (1:1 ratio) gave a much lighter "clean" yellow on approx. 10 % alum! and I am not sure that much more alum is such a great idea - I spoiled one batch years back, because too much alum gives the yarn/fibres a "sticky" feel that can't be taken out again:( not too long ago we had a long discussion on a german dyer's list, where someone with chemical background told us that a lot of alum is never taken up by the wool, so there is no point in going over 10 %, some dyers even go down to only 7 or 8 % of dry weight.
    and if Elinor is starting to loose colour - you can always overdye her?:) a nice (cold dyed) walnut brown might suit her???

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    1. I've had a read around and seen it mentioned in a couple of places that going over 25% alum makes yarn sticky - which sounds like an awful lot. When I started I used to use 7% plus cream of tartar, then decided it didn't make much difference. A proper trial is way overdue, maybe I should go back to that. I think Elinor's wool must be rising, tatty fleece always makes her tetchy. Perhaps I'll suggest she visits a shearing parlour ...

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  2. I've never really liked olivey-green or army-green, but these birch greens just glow from within! Beautiful work again. I am curious too what happens when more alum is added. I will look up washable tags for you and tell you what they are made of.
    I think I left a question in a comment and I can't find the comment, so sorry if I'm repeating myself but I really want to ask: I bought a skein of hand dyed wool and it doesn't have enough speckles for my liking, so can I flick some food colouring speckles onto it and microwave it WITHOUT MORDANTING it? I ask because it has already been pre-mordanted hasn't it? A mordant would have been used when it was dyed by the artist. I'm just curious about the science of it, it's no trouble to add some vinegar to the food dye (which I will probably do just to be safe). In the same way, if I had a skein that was too bright could I sadden it by a slow simmer with iron? Thanks for any help.

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    1. I know very little about acid dyes, but I have the general idea that wool isn't premordanted, citric acid goes in with the dye. Similarly, I don't know the method for adding food dye or even how acid dyes react with iron. Really sorry, but I am no help on this one. Maybe you could test a small portion of your wool and see if you liked the result?

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  3. Oh yes, you're probably right, they'd probably be acid dyes. Hmm, interesting. Thanks Fran I will test a little bit and see how it goes.
    Re. Tags: you might like something made of Tyvek by Dupont. It's PH neutral and made of polyethylene. It behaves like a mix of paper and fabric. Apparently builders use it to wrap houses to protect surfaces while they work, it makes waterproof banners last for ages, art conservators use it to wrap artworks because it protects and breathes. The famous Mother Of All Tags on Etsy, for spinners who want their labels to last through the setting wash, use Tyvek and a permanent sharpie. Maybe you could find an old advertising banner or ask a builder for their offcuts and make some tags. Sounds like you have a good system down anyway. Good luck for the next one!

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    1. Well thanks, I shall be on the look out for tyvek now :)

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