Journal

How to Mordant Wool for Natural Dyeing

Mordanting is the single most important step in natural dyeing. Get this right and your colours will last. Skip it and they won’t.

A mordant works by forming a chemical bond with your fibres and with the plant pigment. Without that bond, there’s nothing to hold the dye in place. Sunlight, washing, time will all cause the colour to drift off. With a good mordant, you get results that are lightfast and washfast.

This is how I do it.

What You’ll Need

• Wool (any weight; I’m using 4-ply sock wool here, 10 mini skeins, 200g total)
• Aluminium potassium sulphate (alum), 8% of the weight of your wool
• Kitchen scales
• A small pan for dissolving the mordant
• A bowl large enough to hold your wool
• A way to tie your skeins together (I use reusable cable ties, but a piece of cotton thread works fine)

A Note on Alum

People sometimes ask whether alum is safe, or say they want to avoid chemicals entirely. It’s worth saying clearly: everything in this process is chemicals. The wool, the water, the plant dye. Alum isn’t dangerous by comparison with some of the alternatives.

Aluminium potassium sulphate has been used as a mordant for centuries. You’ve almost certainly already consumed it; it’s used in pickling and baking, and it’s common in natural deodorants. Compare that to rhubarb leaves, which are sometimes suggested as an alternative and which give off oxalic acid vapour. I’ve used them experimentally, but I wouldn’t use a lot of them.

In Scotland and elsewhere in the UK, club moss was traditionally used because it accumulates aluminium from the soil. It’s now endangered. Please don’t use it. It isn’t more natural or more eco; it’s just harmful to do.

Alum is reliable, well understood, and genuinely safe at the quantities needed for mordanting.

Step One: Weigh Your Wool

Before you do anything else, weigh your wool and write that number down. You need it to calculate how much mordant to use. If you’re using mini skeins, count them; each one is usually 20g, so you can do the maths that way.

I had 200g of wool for this batch. My mordant quantity is 8% of that: 16g of alum.

You’ll sometimes see recipes calling for 15% or more. You don’t need it. 8% is plenty, and using less is better practice all round.

Step Two: Soak the Wool Overnight

Tie your skeins loosely, loose enough for water to get through but tidy enough that they won’t tangle. Put them in a bowl of warm water (roughly hot-tap temperature), pressing them down gently until they’re fully submerged.

Leave them for at least 10 hours, ideally overnight.

Warm water helps the wool absorb moisture much faster than cold. By the next morning, the skeins will look noticeably plumper. That’s what you want; the goal is wool that acts like a sponge, ready to pull the mordant solution right through.

Step Three: Dissolve the Mordant

Weigh out your alum into a small pan. Add a little water and heat gently, stirring until every grain has dissolved. It’s similar to dissolving sugar for a syrup; you’re not boiling it, just warming until it clears.

I do this in a small pan rather than a large one deliberately. There’s no point wasting water or energy heating a big volume when a small one will do.

A separate little camping stove is worth having for natural dyeing generally. It keeps things away from your food preparation area (you should keep all your dye equipment completely separate), and in decent weather you can work outside, which is better. You want good ventilation when you’re heating mordants and dye plants.

Step Four: Add the Wool to the Mordant

Pour your dissolved alum solution into the soaking bowl. Give it a stir so the mordant is evenly distributed through the water.

Now take your skeins and gently squeeze out the water they’ve been soaking in. Not wringing, just a gentle squeeze, enough to create a little space inside the fibres. Lower the skeins into the mordant solution while still squeezing, then release. The idea is that they draw the mordant solution in as they relax.

Top up with water if needed to cover everything, and leave again for at least 10 hours, ideally another overnight.

Be gentle with wet wool throughout this process. It felts easily when agitated.

Step Five: Take the Wool Out

After its time in the mordant, lift the wool out gently (the ties or cable tie help here) and give it a gentle squeeze.

At this point you have two options.

If you’re going straight to dyeing: rinse the wool before you put it in the dye bath. There will be mordant particles that aren’t yet bonded to the fibre, and if you skip the rinse they’ll float around in your dye and give uneven results. A simple rinse sorts this.

If you’re storing the mordanted wool: hang each skein separately to dry completely, then store in a labelled box. Write down the fibre type, the date, and what mordant you used. You will not remember this later. I promise.

When you come back to use stored mordanted wool, rehydrating it before dyeing acts as your rinse anyway.

The Mordant Bath Afterwards

You may be able to reuse the mordant bath by topping it up with fresh alum. Whether it’s worth doing depends on how much mordant you think has transferred into the wool. At 8%, most of it should have been taken up by the fibre, so there may not be a great deal left. Use your judgement.

That’s genuinely the whole process. It looks more complicated than it is because of the chemical name and the waiting. But it’s mostly just: weigh, soak, dissolve, steep, dry. Each stage takes about five minutes of actual work.

I’ve written a step-by-step download that goes alongside this

 

Natural Dyeing with Sweet Cicely

Sweet cicely (Myrrhis odorata) is one of my favourite dye plants, partly because it grows so well here in Scotland and partly because the whole studio smells of aniseed while you are working with it. It likes damp and shade and the shelter of hedges, and in this part of the country it does rather too well. I have a lot of it. Dyeing with it is one way of putting that to good use.

A bit of background

Sweet cicely is probably not a true native British plant. It most likely came over with the Romans, which would explain why it tends to be found near old settlements and buildings rather than in truly wild places. One of its old folk names is “the Roman plant.”

It has a long history of medicinal use. John Gerard wrote in 1597 that it was “very good for old people that are dull and without courage: it rejoiceth and comforteth the heart, and increases their lust and strength.” It was recommended for everything from babies’ colic to giving a general tonic to older women, and the roots and leaves were used as a blood purifier and wound ointment.

It was also used in cooking as a natural sweetener. The compound responsible for the aniseed scent, anethole, is sweeter than sugar, so sweet cicely was traditionally cooked with tart fruit like rhubarb and gooseberries to reduce the amount of sugar needed. During wartime rationing in the Second World War, people went back to foraging for it for exactly that reason.

Identifying it safely

If you are foraging for sweet cicely, please use a proper field guide with photographs and line drawings. Do not rely solely on an app.

The reason this matters is that sweet cicely belongs to the umbellifer family, the group of plants with umbrella-shaped flower heads. Some of its relatives can kill you. Hemlock is the obvious one. Sweet cicely itself is harmless, but you want to be certain.

The things to look for: the leaves are very soft and fern-like, not stiff or spiky. If you bruise them, they smell distinctly of aniseed. The leaves also have pale whitish markings near the base of the leaflets. Hemlock, by contrast, has a smooth stem often marked with red or purple blotching, and no aniseed smell.

Scent and colour

I have noticed that plants with strongly aromatic foliage tend to give good dye colour. Sweet cicely and fennel both smell of aniseed, and both give a bright, clean yellow. It is not a coincidence I think. The same compound, anethole, is responsible for both the scent and the dye potential.

Fennel may work better if you are somewhere warmer and drier than Scotland. If sweet cicely doesn’t grow near you, fennel is worth trying.

The method

This is a spring dye, which means speed matters. Early season leaves give the best colour, and you want to work quickly rather than simmering things for a long time. The fresher the leaves, the brighter the result.

What you need:

• As many sweet cicely leaves as will fit in your pan
• Washing soda (sodium carbonate)
• White wine vinegar
• pH strips or a pH meter
• Pre-mordanted wool or linen
• A stainless steel dye pan

Mordanting: The wool I used was pre-mordanted with aluminium potassium sulphate at 8%. If you want a video on how to mordant, leave a comment and I will make one.

Step one: make the dye bath

Strip the leaves from the stems and pack them into your pan. You want the pan fairly well filled but with enough space for the leaves to move around.

Add approximately one teaspoon of washing soda per large pan of water. The reason for this is that leafy dye baths tend to be slightly acidic, and the washing soda nudges the pH towards alkaline. What you are aiming for is something close to neutral. Add cold water to cover, put the lid on, and bring to just below a simmer. Keep it there for about 10 to 15 minutes. Do not boil hard and do not leave it for hours.

Step two: strain and adjust

Strain the leaves out into a large bowl or pan. Work fairly quickly at this point. Add cold water to bring the temperature down to hand hot.

Check the pH with a strip or meter. If the washing soda hasn’t been fully counteracted by the acidity of the leaves, the bath may still be on the alkaline side. You are looking for something close to neutral, around pH 7. If it reads higher, add a small amount of white vinegar, stir, and check again. Half a capful is usually enough. Do this somewhere well ventilated, as the reaction between the soda and vinegar fizzes and gives off fumes.

Step three: dye

Put your damp, pre-mordanted fibre into the dye bath while it is hand hot. If the bath were any hotter at this stage you could felt the wool, so check before the yarn goes in.

Leave for about an hour. The colour takes up quickly. You are looking for a bright yellow with a slight green quality to it, fairly fluorescent in good light. Linen takes up a similar yellow, slightly flatter than the wool but still good.

Rinse the yarn, hang to dry somewhere out of direct light, and leave for two to three weeks before washing. This settling period lets the dye pigments fully bond with the fibre. After that, wash in a pH neutral detergent.

What you end up with

A bright, slightly yellow-green. Not a dull yellow. This is one of the more satisfying spring dyes because the colour has a lot of life to it.

The linen came out well too. If you prefer to make sample books or dye cloth rather than yarn, sweet cicely works for that just as well.

 

A New Series: Dyeing with Plants

In 2000, I left my job as an art gallery curator, retrained in horticulture, and set up a cut flower business. I grew everything myself - every stem for every wedding, every bouquet sent by post, everything arranged for every event came from this garden in Stirlingshire.

There was one exception. A bride wanted roses at a time when I had none, and we compromised on English-grown ones. Two days before the wedding I got a call to say they’d actually be coming from Kenya. They arrived smelling of chemicals, stiff as sticks, wrong in every possible way against everything else in the arrangement. I never ordered anyone else’s flowers again.

That stubbornness is still here. It’s now just pointed at a dye pot.

What this series is

This is a series about botanical dyeing - specifically about what’s in my dye bath that week. Not a syllabus, not a planned curriculum. I’ll film what’s ready, what’s at its peak, and that’s what we’ll work with. If something is past its best when I get to filming, it waits for next year.

I am plant first, colour second. Most dyeing content starts from the colour you want and works backwards. I work the other way - I look at what’s there, what’s abundant, what’s ready, and I put it in the pot. The colour is what comes.

How I learned, and what I found out about my soil

I learned to dye with Debbie Bamford - the Mulberry Dyer, and a world expert on madder. After that first course, I dabbled for a few years, picking it up and putting it down. It wasn’t until I decided to make a jumper dyed entirely from garden plants that I became properly hooked.

That jumper now belongs to my elder daughter, who wears it a lot. It’s held up well.

I started building a dye garden, and fairly quickly discovered that you couldn’t get much worse conditions for one. We’re acidic, wet, and claggy. Most of the traditional dye plants - weld, madder, indigo - either failed completely or sulked. Dyer’s chamomile does two years here and then gives up. Other people complain it takes over their gardens.

So I did what anyone does when the textbook doesn’t apply: I ignored the textbook. I started thinking like someone who is outside the guild system entirely, way back in time, just looking around at what’s there and giving things a go. And as you can see from this blanket, there’s plenty of colour to be had.

(I do have some madder growing in the polytunnel. It won’t survive outside in my conditions, but I’m hopeful the tunnel will protect it. It takes four years to reach harvestable size, so this is a slow experiment. If it works, it will add orangey reds that I can’t currently get here.)

On taking plants

I don’t forage rare things. Everything I use is either grown here as a deliberate crop, or it’s what I’d call borderline invasive - the kind of plant where, if a thousand people came picking, there would still be plenty of it left. Nettles, docks, bracken. Plants that give without any worry.

What I won’t do is hunt something down because it gives a particular colour if you dig up the root. Roots aren’t forageable. And beyond that, there are so many colours that are just freely given by abundant plants - chasing a pink or a teal from something uncommon is unnecessary, and it’s also a way of exploiting what we’re supposed to be working with.

Resist the novelty. Rein it back. See what you actually have.

What the colours look like

The blanket I’m working on at the moment was started during lockdown. Mini skeins, each stripe a different plant, double-sided, knitted in strips. It’s almost finished - one more stripe to go this year. The colours have surprised me repeatedly. Things I expected to give very little gave a lot. The palette is much wider than people assume when they think about local, foraged dyeing.

The threads on the studio table - dyed embroidery threads from garden and local plants - are what years of this practice produces. There’s a full rainbow in them. No sense of making do, no muted compromise. These are threads worth stitching with, and worth selling.

That’s what plant-first dyeing looks like here, in this particular piece of Stirlingshire, on this particular soil.

What you’ll get from this series

Each film will be about one plant or group of plants - what they are, where I find them, how I use them, and what to expect in terms of colour. Because many of these plants have grown in Scotland for a very long time, there’s often history and folk use attached to them too, and I’ll bring that in where it’s interesting.

If you’re watching from somewhere with different soil, different climate, different plants - some of what I use won’t work for you. That’s fine. The point isn’t to follow my exact plants. It’s to find what’s abundant where you are, and start there.

A Remarkable Textile Exhibition in Paris (On Until July 2026)

 

I ended up in Paris rather by accident. I’d flown to Naples and decided to come back by train: Naples to Turin, Turin to Paris, then through the Channel Tunnel to London. Two days in Paris meant I could see several exhibitions, and one of them was at the Halle Saint-Pierre in Montmartre.

I want to mention the space itself before I get to the work. The Halle Saint-Pierre is an outsider art space: folk art, art brut, things that exist outside the main establishment. It sits in the middle of Paris’s textile district about 5 minutes from Montmartre, it is surrounded by shops selling fabrics, yarns, buttons, zips. And the space itself felt genuinely alive. The bookshop was full. The library was full. The café was busy, there were people having head massages, workshops clearly running. It’s the kind of art space we all want more of.

 

At the moment, right through to the end of July 2026, they have an exhibition called L’Étoffe des rêves (The Stuff of Dreams). Thirty-six textile artists, two floors of work. It’s extraordinary and, honestly, quite overwhelming. I could only take in so much.

So rather than attempt all thirty-six, I want to tell you about three artists whose work stopped me.

Lili Simon

Lili Simon was born in Alsace in 1980. She trained at the Beaux-Arts but her practice has always been more outsider than establishment, taking magazines, catalogues, adverts and subverting them, poking fun at them.

During lockdown, she became interested in needlepoint and started thinking about those very camp, kitsch landscape canvases from the 1960s and 70s. The deer, the mountains, the idealised coastal scenes. Women spending hundreds of hours on these complicated pieces, sitting and thinking. And she started wondering: what are their fantasies? We talk endlessly about the male gaze. But when a woman is sitting stitching for hours and hours, what is she looking at in her mind’s eye?

Lili Simon took some adverts featuring men in their underwear (the Calvin Klein kind of aesthetic) and inserted them into the canvases.

She did this in two ways. In some pieces she has carefully unpicked the original stitches and restitched over them to create her figure. In others she has cut the original needlepoint, made a new panel, and sewn it in. Very different techniques, quite different results.

I found them very funny. Understated. And it occurred to me that this is also a genuine technique for craft activism: taking an existing textile object and replacing elements of it with something entirely unexpected.

Aurélia Jaubert

Aurélia Jaubert was born in 1967 and grew up in a household where looking carefully at things mattered. Her mother, Marie-José Jaubert, wrote La Mer assassinée in 1978, a book documenting pollution along the French coastline. Her father, Alain Jaubert, spent his career making documentary films about how to look closely at paintings. That’s the kind of household this is.

She began her big tapestry works in 2017, after years of collecting old needlepoints from car boot sales and flea markets. She has always found them a bit naff, she says, and also beautiful, and also important. Because all of that needlework corresponds to a condition of women. Right up into the 1950s, there were books about how to be a good housewife and how to occupy your leisure time.

Her ambition from the start was to take all of those small domestic pieces and make something monumental from them, something on the scale of a medieval or Renaissance tapestry, with a foreground, a middle ground, a background, figures, and stories.

The two works at the Halle Saint-Pierre took up an entire wall. They are extraordinary. There is so much to look at: hunting scenes, women in crinolines, classical figures, animals, all assembled from pieces that might span a hundred years of women’s making. She also uses the backs of some sections deliberately, so you see the workings, something like a pencil sketch showing through, which softens the weight of it all slightly.

People were standing in front of these for a long time.

There is a short film on YouTube of Aurélia working in her studio: cutting needlepoints, assembling pieces, walking round and round the work. It’s worth watching.

Shao Liyu Chen

Shao Liyu Chen was born in Beijing in 1946. She grew up in a traditional courtyard house in the heart of old Beijing, in the hutongs, the network of alleyways that ran through the old city. She went to university, became a professor of philosophy, and in the early 1980s her husband left for Paris to study contemporary art. She joined him five years later.

In Paris, she and her husband moved through museums and galleries, absorbing Western art. She began working for a French interiors company, bridging Chinese and Western aesthetics. And then she made a return visit to Beijing and found that the city of her childhood had been largely demolished. Modern towers had replaced the hutongs. The courtyards were gone.

She came back to France and began to make collages. Everything in the exhibition came from her own collection: these pieces were never for sale, never intended for galleries. They are made from tiny scraps of fabric, assembled into dense, teeming cityscapes and landscapes of a Beijing that no longer exists.

The level of detail is remarkable. People stood in front of these for a long time too, finding things: a bicycle, a fire, a dog, a cart. Made from the smallest fragments of cloth.

She is nearly eighty. She came to this work in her forties, after a career in philosophy and cultural work. Everything in the exhibition belongs to her personally. That felt significant.

Why these three

These are by no means the only artists worth seeing in this exhibition. But they are the three that connected most directly to conversations I find happening all the time in The Studio: about repurposed work, about the labour of women, about memory, about what we do with the small scraps of things we accumulate and don’t quite know what to do with.

If you have old needlepoints piling up. If you have a bag of tiny fabric scraps. If you’re wondering what those things are actually for, this exhibition has something to say about that.

The Halle Saint-Pierre, 2 rue Ronsard, Paris 18th. L’Étoffe des rêves runs until 31 July 2026. Open Monday–Friday 11am–6pm, Saturday 11am–7pm, Sunday 12pm–6pm.