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How To Extract Woad Pigment From A Late Harvest | October Woad In Derbyshire

amanda haran

11 minutes ago

8 min read

By Wednesday 28 October 2026, my first woad (Isatis tinctoria) had been in the ground in my front garden in Riddings, Derbyshire, for 191 days, long after most guides say it should have been picked. This is how to extract woad pigment from a late harvest, told through my own first attempt with the hot water method, after a summer that held the plants back. The seeds came from Justine Aldersey-Williams, the tutor on the Growing Slow Textiles course I'm on, where growing woad is part of the curriculum.

Can You Harvest Woad In October? | Woad After A Hot Summer

I sowed the woad on 20 April 2026, the same day as my flax, and grew it between the flax and a row of dill. It was slow to get going. My garden faces full sun and the soil is heavy clay, which baked hard in the sun and cracked to about 4 inches around the crop, the same cracked clay I wrote about in When To Harvest Flax For Fibre. The woad struggled in the summer heat and only started putting on leaves once the rain came back. In Apple Oak Fibreworks' woad trial, the first harvest came three months after sowing, which for me would have meant July, and most guides say to harvest woad between July and September. I left mine as long as I could, aiming to get it in before the first frost. Woad.org.uk says woad can be harvested as late as November in some years, but the first autumn frost may destroy the colour. I'm sharing this for anyone else whose woad had an odd year after a hot summer, or who is harvesting woad late in the season.

The dug woad bed marked into sections with string lines, with a wooden board laid across the soil — Marking Out The Rows | April 2026

Rows of first-year woad rosettes among fallen autumn leaves, with dry flax stems beside them — First Year Woad In Late October

Looking down on a single woad rosette with long, pale-veined green leaves — A Woad Rosette Before Harvest

Why Stainless Steel & Why Not Kitchen Pans?

I had planned to process it the weekend before, but realised the kit I had was used for food, and the instructions said those items weren't suitable. So I pushed the harvest back and bought special equipment just for dyeing. I'd been told to do this, but I didn't really understand why, so here's what I found out.

Stainless steel is used because it doesn't react with what's in the pot. Maiwa's guide to natural dyes recommends stainless steel, unchipped enamel, glass or plastic, because iron and copper react with a dye bath, with iron dulling colours and copper brightening them. Aluminium is the one to avoid with woad, because the liquid is made alkaline with soda ash, and Botanical Colors explains that stainless steel normally stands up to alkalinity, while a pot that corrodes in an alkaline vat is probably aluminium. Keeping dye kit away from food is a precaution against residues. Whatever goes into a dye pot, from the leaves and soda ash now to the lime for the vat later, can cling to the surface, especially in scratches and seams, and there's no easy way to be sure a pot is clean enough to cook in again. Spin Off magazine advises never using a dye pot for cooking, or a cooking pot for dyeing, and the same goes for spoons, lids and measuring tools. Woad isn't grown as a food plant either, so the simplest thing is to keep the two sets of kit completely apart.

Harvesting Woad In October, In The Rain

On Wednesday 28 October I cut the leaves between showers, straight into a colander, finishing at around half past three. It was a wet day and the leaves were still wet when I weighed them. A few were over 6 inches long, and some had holes in them from critters. I left a crown in each plant, so hopefully it will grow again next year. Woad usually flowers and sets seed in its second year rather than giving another crop of leaves, and I have no idea yet about getting seed from it.

A hand cutting woad leaves with green scissors beside a steel colander half full of leaves — Cutting Woad Into The Colander

Close-up of wet woad leaves with small holes made by insects — Insect Holes In The Leaves

I took out the yellow and damaged leaves, checking twice, then tore the rest by hand into palm-sized pieces and removed the thick stalks, which went on the compost with the yellow leaves. As I sorted and tore them, I kept finding slugs, so I took the slug laced leaves outside so they could live another day. I didn't wash the leaves, as they looked clean after the rain. The colander weighs 223 g and the scale read 1,458 g with the leaves in, which left 1,235 g of fresh woad leaves.

A colander of thick woad stalks and yellowed leaves removed before steeping — Stalks & Yellow Leaves Taken Out

A hand holding torn woad leaves above a pile of prepared leaves — Tearing The Leaves By Hand

How To Extract Woad Pigment | The Hot Water Method

I had to choose the hot water method because I planned to dye flax or linen. The other way to get blue from woad is to dye straight from the fresh leaves, without extracting any pigment first. Methods vary: some dyers tear or blend the leaves into cold or iced water, sometimes with salt or a little vinegar, while others heat them briefly. The wool or silk goes straight into the liquid, comes out green and turns blue as it dries in the air. It's quicker and needs no soda ash, but it only works while the leaves are fresh, and it suits animal fibres. At Kaliko, wool and silk came out of a fresh woad bath green and dried to pale blue and turquoise, and the leaves can't be dried to use in winter. Sew Historically tried fresh leaf methods on cotton and linen and found they didn't work, with the salt method leaving a green that never turned blue. Extracting the blue pigment first means I can keep it and use it later in a fruit and lime vat, which is how I plan to get the colour onto my flax and linen.

Just after 4 pm the leaves went into a large stainless steel pot with about 5 litres of water at 80°C. I turned the heat off, pressed the leaves down and put the lid on. The smell was strong, a bit like cabbage, and much stronger once the leaves were steeping, but because I know what retting flax smells like in water, I thought it wasn't too bad. By half past four the liquid looked like very weak tea and had dropped to 67°C, and at about quarter to five, after roughly 43 minutes, it had turned a deep amber, the colour of sherry.

A digital thermometer reading 80°C in a stainless steel pot of hot water — Water At 80°C

A spoon pressing fresh woad leaves down into hot water in a stainless steel pot — Pressing The Leaves Under

Then it had to cool quickly. I stood the pot in a sink of ice and cold water and gently mashed the leaves, and it came down to 49.4°C in about eight minutes. I strained it through a wet old tea towel in the colander, squeezed the leaves out and put them on the compost too.

A kitchen sink filled with cold water and ice cubes ready to cool the pot — Ice Bath Ready In The Sink

A thermometer reading 49.4°C in dark amber woad liquid with steeped leaves and a whisk — Cooled To 49.4°C

Steeped woad leaves in deep amber liquid, strained through a printed tea towel lining a colander — Straining Through An Old Tea Towel

Adding Soda Ash | pH Testing For The First Time Since School

I've not done pH testing since I was at school. The strained liquid tested at about pH 5, so I added soda ash dissolved in hot water a little at a time, and about a third of the solution took it to pH 10, when the colour shifted to green. Then I whisked hard for 20 minutes. Wisps of blue appeared through the froth and the liquid underneath turned bluey green, so I covered the pot and left it to settle overnight.

Two pH test strips on brown card, one yellow and green from the acidic liquid, one purple and blue green after adding soda ash — pH Before & After Soda Ash

A whisk beating dark woad liquid into froth in a stainless steel pan — Whisking For 20 Minutes

As I went, I filled five small glass jars with a pipette, so the colour change is there to see. They run from pale gold at the start of the steep, through deep amber and the strained liquid, to green after the soda ash and bluey green after whisking.

Five small glass jars in a row on a linen cloth, showing woad liquid changing from pale gold to amber to dark bluey green — Five Jars, Gold To Bluey Green

Waiting For The Woad Pigment To Settle

The next morning a blue grey crust was floating on the surface, with blue showing at the edges where it caught the light, and the liquid was still bluey green. I skimmed some of it off into a glass jar and left the rest to settle. Two days on, I've still left the pot settling. There was less scum this time, but it still looked blue, as if the particles were in suspension. Pouring off the liquid and collecting the woad pigment comes next, and the plan is to dye flax and linen with it later, in a fruit and lime vat.

Blue grey woad pigment floating on dark liquid in a steel pot the morning after whisking — The Next Morning

A glass jar holding dark liquid with blue woad pigment skimmed from the surface of the pot — Skimmed Surface Pigment

Flecks of blue woad pigment on dark liquid, with condensation inside the rim of a steel pot — Blue Flecks On Day Two

Easier Than I Thought

I must admit I was a little apprehensive before I started, and wondered about the danger of the process. I'm not known for relishing danger. Luckily I didn't need to put my knickers on the outside of my old clothes, as it was well within my capabilities, but I did use gloves and goggles, took my time and read the steps a few times to make sure I knew what I was doing and why. I found the whole process easier than I thought it would be, but it's all about being prepared: having the right kit in the right place, and being ready to time things. I'm pants at timing things and usually wing it, so this was a new discipline.

The real dangers are fairly ordinary ones. The biggest is the heat, because about 5 litres of water at 80°C is enough to scald, and the pot has to be moved into the ice bath while it's still hot. Soda ash is the same chemical as washing soda, but its safety data sheet says it causes serious eye irritation and can irritate skin, which is why goggles matter most when it's being dissolved in hot water and added to the pot, where it can splash. Rubber gloves are the only protective kit on Woad.org.uk's list of what you need for extraction. The stronger alkali comes later, because the lime used in a fruit and lime vat is caustic, so the dyeing stage will need the same care again.

My First Woad Extraction In Numbers

Sown: 20 April 2026, in Riddings, Derbyshire
Harvested: Wednesday 28 October 2026, after 191 days in the ground
Fresh woad leaves: 1,235 g
Water: about 5 litres at 80°C, heat off
Steeped: about 43 minutes, until deep amber
Cooled: to 49.4°C in about eight minutes in an ice bath
pH: from about pH 5 to pH 10 with soda ash
Whisked: 20 minutes, until blue showed in the froth
Settling: still going two days later
Pigment yield: to follow

This is my first attempt, in one garden after a strange season, not a controlled trial, so these are my own numbers rather than a recipe.

Thank You

Thank you to Justine Aldersey-Williams for the seeds, and to the Growing Slow Textiles course for making woad part of the growing curriculum.

If your woad had a strange season too, or you've harvested yours late, I'd love to hear how you got on. I'll share how much pigment I collected once the pot has finally settled.