Friday, 22 June 2018

Cold Water and Vinegar Dyeing with Woad and Japanese Indigo Leaves

Yesterday morning, the sun shone after a wet week. Inspecting the raised border in my front garden, I realised that though I can rely on the Japanese Indigo plants to crowd out most weeds, a random self-seeded courgette hidden among the rhubarb had started spreading its leaves over their heads.
The garden has been coming on exceptionally well, thanks to a bitterly cold winter and a warm, dry spring, both of which have seriously hindered the local slug population. In the midst of much smug self-congratulation, I bent down to weed among the woad plants at the front of the border and found the wretched beasts had taken their chances during the rain and slimed and climbed up the boards to eat half my leaves.
Deciding to make the most of what woad was left, I put some sections of merino and silk tops in the sink to soak while I walked the dog. In the past, I've used method of extracting dye from Japanese Indigo leaves which only uses cold water and vinegar, so when my harvest only amounted to a modest bowlful of leaves, hardly worth a proper vat, it seemed a good time to find out whether this simple method would work on woad. The leaves had a quick rinse under the cold tap then were torn up and buzzed in a blender with ice cold water and poured into a bowl with a glug of white vinegar. After standing for half an hour, the green slush was squeezed, massaged, sieved through a cloth into a fresh bowl then the last of the juice was squashed out of the pulp through the cloth.

I put in a 15g section of wet merino and silk tops and left the bowl in a cool spot while I added another litre of cold water and vinegar to the lump of leaf pulp and left that to stand for another half an hour before repeating the squeezing and sieving and adding more wool to a second bowl.

Meanwhile, not a lot was happening in bowl one, where the wool tops were sodden with green juice, but not appreciably blue. After an hour, I squeezed out the fluid and encouraged by the sight of pale turquoise, put in my third length of tops to get the benefit of whatever indigo might still be available.

At the end of the process, none of the three lengths of fibre appeared strongly dyed and I suspected that once they had been rinsed, I would have even less colour to show for my efforts. Still, they hadn't been enormous efforts and I'd got quite a bit of gardening done in the intervals. Maybe June is too early to harvest woad, despite the warmth earlier this year. The Japanese Indigo plants had definitely already developed indigo within their leaves, I could see dark blue staining wherever I had bent or bruised a leaf while weeding. The afternoon was still young and I had all the kit out, so I cut a bowlful of Japanese Indigo plant tops weighing 300g and repeated the whole process for the sake of comparison.

This time, the fluid seemed more viscous and blue green and after an hour soaking, the first 15g strip of fibres had turned a more convincing blue beneath the surface sludge.

The Japanese Indigo was working so much better that I didn't stop after dyeing twice with the first pressing and once with the resoaked leaves. I combined the two bowlfuls and left another section of tops in there all evening, took that out and put yet another bit in to soak overnight. This morning, the wool was a much more familiar indigo blue and the fluid still looked as though there was oxgenated blue indigo in it, but enough is enough, I chucked it out. There's plenty more leaves growing in the garden and I'm not convinced these cold indigo dyes fix as well and are as stable as the blues from a hot, deoxgenated vat.

Here are the results of the cold water and vinegar method, woad at the top and Japanese Indigo at the bottom, first pressing then second pressing of leaves followed by dyeing in the afterbath.

I won't rinse them til tomorrow, so I'll have to add another picture later to show the colours once the residual leaf slime has come off. First thought - woad leaves don't work nearly as well as Japanese Indigo for this method, in future, I'll process them properly or not at all. Second thought - Ionger soaking gives stronger colours when using Japanese Indigo. Third thought - I really mustn't neglect to do a proper light fastness test this time. Fourth thought - slug pellets.

Friday, 15 June 2018

Dyeing Wool with Almond Tree Bark

"So, how was Spinning Camp?" My companion, Elinor Gotland, had been watching me lug the tent back into the garage and load the washing machine. A cup of tea in the shade provided a welcome break.
"Brilliant. I've been getting sunburnt, felting soaps and impersonating dinosaurs."
"Ooo, you don't usually get good enough weather for that."
"Did a bit of spinning too."
"Yes, I saw you unpacking two new fleeces. I thought the car boot was going to burst."
"Hmm, well, things would have been worse if I'd stayed long enough to go to the Fleece Fair."
This morning found me intending to water the dye garden, set up a suint vat and write this week's blog. Before I went away, I dyed some skeins of wool yarn in a vat of almond tree bark. Now they need a rinse and proper consideration, so though they aren't as thrilling as fleece shopping or a pterodactyl attack, I thought I would write a post recording the process before I forget.

Three almond trees were doing nicely in the front garden until a few years ago when they contracted a disease that makes the new leaves blister and curl. This spring, the poor things had more dead branches than healthy ones. When we cut one tree down, I thought I would peel off its bark to try making dye, only there wasn't much that hadn't already shrivelled and dried onto the heartwood.
About 300g was left in a pot of water to ferment for a week then simmered for an hour. The dye bath looked cloudy orange and indicator paper showed it had become mildly acidic at pH 5. I put in three skeins of bulky yarn weighing 150g in total, simmered them for an hour and left them overnight. I took one out and was neither surprised nor upset to find it had gone beige.
Past experience of bark dyes has shown that increasing the pH of the fermented bath to neutral can greatly improve the dye colour. Samples of my almond bark dye bath shifted from orange at pH 5 to red at pH 7, while adding enough soda ash to bring the pH up to 9 made the fluid deep red/brown. I simmered the two remaining skeins at neutral pH, took one out and then added more soda ash before simmering the last skein.

Here is how they looked today, draped over one of the surviving almond trees. On the left, beige from the acidic dye bath, in the middle, a warmer orange beige from the pH neutral bath and on the right, brown from the alkaline bath. Unremarkable I think, pleasant is the kindest comment one might make about almond bark dye. 
Frankly, I would rather have almond blossom in spring and nuts in autumn, failing that, hoping to avoid recurrent disease, I think I shall replace the trees with hazel, hawthorn and maybe eucalyptus. Might get some dye out of that, even if the weather goes back to damp grey normal.

Friday, 8 June 2018

Reusing an Alum Mordant Bath

At great risk of becoming repetitious, I shall once again describe my current quandary. At this time of year, I mordant wool and silk in bulk, ready for the dye plant flowering season. Using 10% of the dry weight of the fibres in alum crystals, sometimes I hot mordant in a large pot of water by simmering for an hour, more often, I cold mordant by leaving fibres to soak in an unheated bath for 24 hours. Last week, I made a dye bath with dried Dyers Chamomile flowers and tried a direct comparison. The wool which had been mordanted hot took up more of the plant dye than wool which had been mordanted cold. I had to conclude that putting my new supplies through a hot mordant process would give me the best results.
Prior to that, when dyeing with birch leaves, I had discovered that increasing the percentage of alum premordant to 15 or even 20% made little difference. I understand that fibres will only pick up half the alum from any mordant bath, whatever the concentration, though I don't understand quite why that should be so. I like to use things up rather than throw them away and having read that alum mordant baths can be reused, I've got into a routine of dividing the things I want to mordant into seven equal portions. I weigh out and dissolve sufficient alum to mordant four portions and after I have finished either the hot or the cold process, I mordant the next two portions in the remaining alum, and finally, repeat the process with the seventh and last portion before chucking out the solution. 
Though I have been growing common dye plants and foraging for others for some years, I still get unexpected results when I am dyeing. This can be all very lovely and serendipitous or all very beige and disappointing, either way, I accept unpredictability, it adds to the thrill. This does not mean I am overjoyed to suppose that some of my duller and dimmer plant dye results may have been the entirely predictable consequence of substandard mordanting practice. I do prefer life's rich tapestry to be a rich tapestry.
This week's trial was a second comparison of hot versus cold alum mordanting plus a comparison of the outcomes of dyeing yarn mordanted in the second and third reuse of hot and cold alum baths. All skeins are DROPS wool, for both the hot and cold process, 50g yarn was mordanted in 5g alum, 25g was mordanted in the leftover mordant bath and then a 12.5g skein was mordanted after that. For the dye bath, I soaked and simmered 100g dried coreopsis tinctoria before adding 100g wool yarn. 

Here are the results. The two larger skeins at the top both had the first use of the alum, the topmost skein in a hot bath and the one below in a cold bath. As before, the hot mordanted skein is an appreciably deeper colour than the cold. The two skeins in the middle were mordanted in the second use of the hot and the cold alum baths and the the two at the bottom had the third use. The very last skein from the third use of the cold bath was left more than 24 hours, I forgot to take it out so it soaked for two days. That one is a slightly darker ginger. I have peered at the others and held them up together and I cannot really tell them apart without reading the labels. They are all much the same as the skein from the first use of the cold alum mordant bath. Which is good news. It suggests I can reuse my alum solutions without sacrificing even more quality of plant dye results and that quite possibly, leaving things to soak for more than 24 hours will improve the results from all my cold mordant baths.

My companion, Elinor Gotland, came upstairs to help me sort through my stash.
"It's high time you cracked on with mordanting all this stuff, Beaut. June is busting out all over the garden."
"At least I know what I am up to now. The expensive yarns can have first go in a hot alum mordant to ensure the best dye results. Then for the others, I'll reuse the remaining bath cold rather than heating it over and over again, because there doesn't seem to be much difference between results from hot or cold reused baths. All the wool and silk tops will have a cold mordant because it works well enough and won't risk felting them. When I reuse the alum cold, don't you think I'd be better off leaving things to soak for two days rather than one?" 
That last question was disingenuous. As I cold mordant things in the household bath, three uses of alum for 48 hours apiece would put the bathroom out of action for nearly a week, which might be pushing my luck. Happily for me, Elinor was too busy fossicking about with my stuff to put two and two and two together.

"What about this beautiful length of heavy tweed from Cambrian Wool?"
"That will have to be mordanted cold because I haven't got a big enough pot for the whole thing and I don't want to cut it til I've decided what it is going to be."
"Oh, I can already picture its perfect destiny, Beaut. These base colours are bound to suit me. I think you should overdye them with Goldenrod and make me a tailored jacket and matching bag."
"All that from half a meter?"
Elinor bridled.
"I have a very slender physique once my fleece is shorn. This summer, my stylist has suggested a dynamic short cropped back and sides with shag cut locks framing my face. A contemporary spin on the gamin style I used to favour in my catwalk days in Paris."
A diplomatic nod seemed safest. I'll just scour the tweed and see how much it shrinks. Elinor's modelling career ended some time ago and she may discover June has been busting out elsewhere. 

Friday, 1 June 2018

Hot versus Cold Alum Mordant for Wool before Dyeing with Dyers Chamomile

I came in out of the rain, pulled off my Wellingtons and announced with some satisfaction
"Soon as we get some sunshine, the Dyers Chamomile plants will be covered in flowers. This time next week, I shall be transmuting base wool into gold."
My companion, Elinor Gotland, put down her book to wipe droplets of water off her specs.
"You've already transformed the kitchen floor into a mudbath, Beaut. Couldn't you put a towel over that dog before she shakes herself again? I've already had a bath this morning."
"You'll have to make do with showering for the next few days. I'm going to take over the bath to mordant all the undyed yarn I bought at Wonderwool."

Elinor rolled her eyes, but she wasn't surprised. It has become my habit to mordant in bulk before the dye plant flowering season begins. When mordanting large quantities, I add the alum to water in the bath in my bathroom. Himself does make me promise to rinse it out afterwards, though considering the distinctive aroma he develops while cycling in lycra, I wonder if alum's long history of use as a deodorant might mean his bathing in it could be a good thing. Anyway, I divide up the fibres I want to mordant into seven equal portions, then weigh out and dissolve sufficient alum to mordant four portions. For example, if I had 700g yarn, that would mean dissolving 40g alum to mordant 400g of it at 10% by weight. I leave the wool to soak in the bath for 24 hours. I understand that fibres will only pick up half the alum from any mordant bath, whatever the concentration, though I don't understand quite why that should be so. This means that once the hypothetical 400g of wool has been taken out, there would still be 20g of alum in the bathwater, enabling me to mordant another two 100g portions of wool by leaving them in there for the next 24 hours, then finally the seventh 100g portion has its day of cold alum mordanting in the remaining 10g alum. Although by this logic 5g of alum must remain in the bathwater after the last skein is mordanted when I pull out the plug on day four, I can feel gratified to have minimised the cost, wastage and pollution involved in the alum mordanting process.

Wool tops, roving and fleece are less likely to become felted during cold mordanting than hot simmering and the bath is ideal for big quantities, especially if I want a large piece of fabric to float freely and mordant evenly. The process does work, I've been using plants to dye cold mordanted wool and silk for the last five years and not noticed a problem.
Recently, however, I have begun to suspect that cold alum mordanting may not result in such strong final dye colours as when alum is used with heat. As a small trial before a major mordanting session on this year's haul of silk/wool blends and superfine Falklands yarns, it seemed timely to make a direct comparison using good old DROPS 100% wool aran yarn.

Two 50g balls were made into four 25g skeins and tied loosely at four points, soaked with a bit of detergent to scour them, then rinsed and soaked overnight. In order to be as precise as possible with tiny weights of alum crystals, I dissolved 20g in 200ml boiling water to make a solution containing 1g per 10ml, then used a syringe to draw up 50ml to be sure each bath got the same amount of alum.
Two skeins of yarn went into a pot of water with 5g alum and were heated up, simmered for an hour then removed and rinsed once the water had cooled to hand hot. The other two skeins went into a bowl of cold water with 5g alum and were soaked in there for 24 hours before rinsing.

Dried Dyers Chamomile flowers can be kept for years in a paper bag and will still release their dye when soaked and simmered. My impression is that the dye per weight of dried flowers is stronger if you use them within a year, though it is hard to be absolutely sure, when so many factors influence the amount of dye an individual flower contains - where the plant grew, whether it was picked in June or August, whether that particular month or year was hot or cool and damp. What is clear to me is that fresh flowers give much more dye than dried ones, because even though they weigh so much less after drying out, it still takes about double the weight of dried flowers to fibre to impart a strong colour. They are still worthwhile having, because picking a plant bare even when you aren't ready to dye does mean it will go on producing new flowers throughout the summer and drying them does provide supplies for times like the present, when no fresh flowers are blooming.

For this trial, I soaked 100g dried Dyers Chamomile then simmered the pot for an hour to extract the dye before adding one 25g skein of wool mordanted with hot alum and one 25g skein that had been mordanted cold. After simmering for an hour, as soon as they had cooled enough to handle, I pulled up lengths of wool from each skein to have a look at their dye colour.

"So, you won't be hogging the bathroom after all, then, Beaut?"
"There's no need to look so pleased about it, Elinor. The cold mordanted skein has still picked up a decent yellow."
"Not as good as the hot one though, is it?"
"The two skeins might even up after I've left them in the pot overnight. Or if I added some soda ash to alkalinise the lot and make the whole dye job brighter. Or maybe I shall just have to hot mordant everything if I want the best results. What a bloody palaver it all is." I turned away and traipsed back into the house. My companion followed.
"Come on, let's put the kettle on, have a cup of tea and a cigarette. Hot alum mordanting isn't the end of the world."
"I don't want to be forever turning on the gas and heating pots up, I wish I didn't have to bother with mordanting at all. I don't really like having to buy any chemicals. I've read about plants like mosses and heuchera that concentrate natural alum from the soil, but I never did grow any. I wish I had, it would be so much more authentic to grow my own mordants."
"More authentic? Authentic how?"
"More traditional, I'd like to use processes that predate industrialisation."
"Hmm, the Industrial Revolution began in the eighteenth century, Beaut. I think you'll find British dyers were mordanting with alum crystals long before that."
"Oh, surely not."
"It's a matter of record which you'd already know if you'd read the classics. Pliny the Elder wrote plenty about alum and its uses. It didn't come from plants in his day, he called alum 'a sort of brine, which exudes from the earth.' The Romans probably brought some with them when they invaded Britain over two thousand years ago. There wouldn't have been anything half so good locally for mordanting the wool from all our sheep. More than likely the British tribes had already been importing alum along the ancient trade routes before the Romans ever turned up. Iron Age Brits were already drinking wine and eating olives, so I expect they would have been pretty interested in trading for Mediterranean alum too."
"Why wouldn't they have made their own British alum?"
"Ah, well, it's all the rain, see, Beaut. Alum dissolves in the wet, so you wouldn't find crystals lying about on the ground anywhere in the UK. You have to get much more modern for evidence of local suppliers. It wasn't til the seventeenth century that someone cornered the market by extracting alum from shale in North Yorkshire and got a British monopoly going." 
We drank our tea and had a contemplative smoke. 
"Feeling better now, Beaut?"
"Well, yes, I suppose I am. If my ancient ancestors had to sort out how best to buy and use alum, then I can do it too." 
"That's the spirit. For a minute there, I thought you were going to insist on growing your own tea and tobacco."

Friday, 25 May 2018

Dyeing Wool with Birch and Plum Tree Leaves using Alum Mordant at Various Concentrations

Not long ago, I accidentally mordanted some Shetland wool yarn using 20% of the weight of the wool in alum crystals, instead of my usual 10%. I thought the amount of colour the yarn picked up from a dye bath of birch tree leaves looked far more impressive than the colour on a smaller skein of the same yarn that had been dyed in the same bath after being mordanted with 10% alum. 

Over a cup of tea in the garden, my companion, Elinor Gotland, quite agreed.
"The little skein looks crap compared to the big one with more mordant. Looks like you've been spoiling the ship for a ha'porth of tar, Beaut. Speaking of ha'porths, how much does alum actually cost?"
"Well, very little actually. I paid about £12 for a kilogram, so even if I didn't reuse the solution, the difference between using 10g or 20g of alum to mordant 100g of wool would be 12 pence. I'm not so fussed about the money, so much as the environmental cost of using more."
"Oh, for heaven's sake, aluminium is the most abundant metal on earth and you're always harping on about how you exhaust your mordant solutions by reusing them three times. Do yourself a favour and get the best out of those plant dye baths you spend half your life brewing up. Making mouldy colours is a waste of all the natural gas you burn, simmering dye pots for hours on end."
"Hmmm. Maybe you've got a point, Elinor. I've read older dye recipes where higher percentages of alum seem to have been standard practice. Along with Glauber's Salts and a whole range of other stuff you don't see in the chemists' anymore. Perhaps the old girls had the right idea all along."

My accidental 20% alum mordant bath included some 50g skeins of Drops Alaska aran wool yarn. I mordanted a couple more skeins with 15% alum and 10% alum and then collected another 150g birch tree leaves while out walking the dog. After simmering the leaves for an hour, I added an equal weight of yarn and half a teaspoon of soda ash to bring the pH just above neutral, simmered the wool in the pot for an hour and left it to soak overnight.

Once the yarn had dried, there wasn't much difference between the three skeins. They were all more yellow and less green than the previous birch leaf dye, which may be because the leaves are no longer so very newly grown. The skeins were tagged, so I knew the one on the left of this picture was mordanted with 10% alum and could see it was only very marginally yellower in tone and slightly paler than the one on the right, which had been mordanted with 20% alum. This made it clear that I hadn't managed to replicate the conditions which produced the contrast between the original 20% versus 10% mordanted skeins. Above and beyond that, it made no sense to me that the skein in the middle, which had been mordanted with 15% alum, looked paler than either of the others.

Obviously, first thing to do was to repeat the test. No flowers are anywhere near blooming in the dye garden, but the plum trees espaliered against the wall needed their tips soft pruned this week. I used to get yellow dyes from the leaves of the apple trees that grew there before, so this seemed a good opportunity to test the dye potential of my plum tree leaves as well as repeating the alum mordant assessment.

150g fresh plum tree leaves were simmered in water for an hour. They released no perceptible colour into the dye bath and its pH tested as mildly acidic. I put three skeins of yarn into the clear fluid, although I only had 25g mordanted with 10% alum, and simmered them for an hour. Next morning, they looked pale yellowish green. When I rinsed them in plain water the yellow grew stronger as the acidic dye bath was washed out, so I gave them a final soak with half a teaspoon of dissolved soda ash. The alkali turned them a proper lemon, paler and sharper than the colour from birch leaves.

No two ways about it, the mordant results were essentially the same, only more pronounced. The 10% skein on the left of the picture is only marginally paler than the 20% skein on the right, while the 15% skein in the middle is paler than either of them.

"From the looks of that wool, you might as well carry on mordanting with 10% alum, Beaut. Don't bother increasing to 20%, save your 12p and spend it on a teabag." My companion gazed sorrowfully into her empty teacup. "I know it's wildly extravagant of me to expect a second cup of tea to have any colour in it."
"A second cup? Your teapot must hold the Welsh record for continuous use. It doesn't go cold all day."
The unsatisfactory tea concentration provided by Elinor's reused teabag did set me thinking. Does reusing an alum mordant bath really have just as good an effect as the first use? Could that original small pale skein have resulted from mordanting the wool in a reused alum bath? On reflection, I remembered that the 15% alum skeins of wool were mordanted cold, whereas both the 20% and the 10% alum skeins were mordanted by heating. These days, I often mordant wool without heat. It does seem to work, but I've never directly compared the dye results after mordanting wool by simmering in alum for an hour against the dye results on wool mordanted by soaking in a cold alum solution for 24 hours.  Maybe cold mordanting is why the 15% skeins came out so pale. Maybe in the original birch leaf dye bath, the little 10% alum skein was mordanted cold in a reused bath of alum.

No good speculating, I think I am going to need to do another trial to try to get clear on this point before the dye garden comes into flower. Still a few weeks to go yet.

Friday, 18 May 2018

Hammered Leaf Prints Made Fast with Iron Solution

Every May when the trees come into leaf, I find myself full of enthusiasm for their loveliness and inclined to start collecting some for hammer printing. Then I work away on a piece of cloth and soon remember hammering is a noisy business that rapidly grows dull and find I've chosen the soft, squashy kinds of leaves which get mashed into the fabric or dryer ones that barely leave a mark, no matter how I thump them. A lot of trial and error gets repeated every year for transient rewards, having found from past experience that the pretty fresh green hammer leaf prints will fade to pale beige within a few months of exposure to light. 

This year, I was encouraged to experiment again after checking my friend's curtains. Last year, I hammer printed leaf borders for them on mordanted fabric, then dyed the fabric in a bath of meadowsweet flowers with added iron, which turned the prints into brown silhouettes. Rather to my surprise, they haven't faded despite the sun shining through them all year, the curtains look much the same as when we hung them up last May. It seems to me that the leaf juices must have been able to pick up and concentrate the iron that was in the dye bath, as I know iron is a particularly lightfast mordant for plant dyes. This year's experiment was intended to find out whether it is necessary to premordant the cotton fabric in order to make iron hammerprints permanent.

First I mordanted one piece of cotton curtain fabric by simmering it for an hour in a solution of aluminium acetate at 5% the weight of the fabric. Then I made a dye bath by simmering 100g of silver birch leaves in water with a teaspoon of soda ash to increase the pH. Next, I collected leaves and wedged a board on a garden wall to provide a solid surface for hammering.
Using an old shirt to lay over the leaves, which were laid reverse side down on my curtain fabric, I thumped away until the juices had soaked through the shirt showing a complete leaf shape, lifted away the shirt then peeled off the leaves. After that, I did much the same to two more pieces of the same fabric which hadn't been mordanted.

One of the unmordanted pieces was just heated in water with a splash of dissolved iron. The other went into the birch leaf dye bath together with the mordanted piece and a slug of dissolved iron.

And here is how they turned out. On the left, the alum premordanted fabric has taken up the birch leaf dye with iron as a khakhi background colour and the leaf hammer prints have taken up both the modified dye and extra iron and gone brown. In the middle, the unmordanted cloth that went into the dye bath has picked up a tinge of background colour while the prints have gone brown. Finally on the unmordanted cloth that was heated in iron and water only, you can see the leaf juices in the hammer prints have taken up iron from the water to make grey silhouettes of variable darkness, presumably according to their affinity for iron.

Japanese Acer leaves make a pink fresh print with no apparent colour along their veins, yet the juice in the veins must picking up more iron, as the veins come up much darker than the rest of the leaf.

In future, I think I shall experiment more using unmordanted cloth with just an iron and water bath. The leaf prints go black within ten minutes of heating and you can rinse the cloth straightaway, getting rid of most of the residual iron on the fabric without washing out the leaf shape. Quick and easy method for making rather a striking contrast print. Might be nice to put a single leaf silhouette on a shirt. Or cover up a stain on the front.

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.