Woad Extraction

 

change text size?

buy woad kits

Buy a kit as a gift

Buy woad watercolors!

Woad watercolors

Woad home > woad extraction

How to Extract Woad Dye in 12 easy stages

Teresinha with woad-dyed jumper & woad plants | Woad.org.ukExtracting woad is something you should try at least once as it is so exciting. To get the blue pigment from woad, it is important to use leaves from the plant’s first summer. Harvest the leaves in late July and August, preferably during a warm spell. Leaves need to be fresh and should be used as soon as possible after harvesting as the pigment can deteriorate rapidly. Having said that, I have had dyers telling me that they got some blue from second-year plants and from dried leaves.

The woad leaves don’t have a blue pigment inside them. Instead they have a ‘precursor’, a chemical that can be transformed into the blue pigment. There is a higher concentration of precursor during a hot spell of weather and this is the best time to harvest the leaves. As it starts to get cold in the autumn, the amount of precursor decreases and after the first frost there is hardly any woad precursor left in the leaves. Most of the precursor disappears by the time the woad plant is in flower in its second year.

By steeping the woad leaves in warm water you break down the waxy coating on the leaves and release chemical precursors into the water. When you add soda ash, you raise the pH making the solution alkaline. When you whisk the solution, you add oxygen. This creates a chemical reaction that forms the woad pigment. This pigment is insoluble in water and it settles on the bottom of the container. You can read more about the chemistry of woad extraction here.

The yield depends on the soil, how well the plants are fed and how warm the summer is. One woad plant produces about 700 grams of leaves and you will get between 1 and 4 grams of blue pigment from 1 kilo of leaves. 1 gram of woad will dye about 20 grams of fibre.

List of requirements for woad extraction

Cutting woad leaves with secateurs | woad.org.uk

1. cutting woad leaves

Tearing woad leaves  | woad.org.uk

2. tearing woad leaves

Torn woad leaves | woad.org.uk

3. torn woad leaves

Steeping woad leaves in hot water | woad.org.uk

4. steeping woad leaves

Cooling woad liquid in sink with ice | woad.org.uk

5. cooling liquid with ice

Straining woad leaves in a colander | woad.org.uk

6. straining the woad liquid

Squeezing liquid from woad leaves | woad.org.uk

7. squeezing woad leaves

Adding soda ash | woad.org.uk

8. adding soda ash

Measuring pH of woad liquid | woad.org.uk

9. measure pH

a) To harvest the leaves and extract the pigment you will need:
- secateurs
- 10 litre stainless steel saucepan or stockpot
- rain water (optional)
- thermometer
- ice cubes (optional)
- colander
- rubber gloves
- bucket
- Pyrex jug
- soda ash
- pH paper
- plastic plant pot (with holes in the bottom) or a hand whisk
- woad leaves :-)

b) To settle and clean the pigment you will need:
- plastic yogurt pot
- several empty coffee jars
- glass siphon (turkey baster)
- funnel (optional)
- piece of habotai silk (optional)

12 Steps to Extraction of Woad Dye
A. Harvesting woad leaves & preparation (this page)
 1. Harvesting woad leaves

 2. Tearing the woad leaves

 3. Steeping the woad leaves

 4. Cooling the woad liquid

 5. Straining the woad liquid

 6. Adding soda ash

B. Extracting the woad pigment (opens a new page)
 7. Aerating the woad liquid
 8. Settling out the woad pigment
 9. Cleaning the woad pigment
10. Drying the woad pigment
11. Filtering the woad pigment
12. Dyeing with woad
 
1. Harvesting the woad leaves
July and August are the best months for harvesting woad in the UK. Cut the leaves from first year woad plants with secateurs, near to their base (fig. 1), and cut enough leaves to fill a plastic carrier bag (about 1250 grams of leaves). Wash the leaves well. If you have a water butt full of water you can put the leaves in the water butt; the leaves will float and you can swish them about to clean them.

2. Tearing the woad leaves
Tear the leaves by hand (fig. 2) but don’t tear them too small (fig. 3) otherwise they will go through the colander later on. There is little blue in the stalks and if you have more leaves than will fit in your saucepan you can remove all of the stalks. Process the leaves as soon as possible after harvesting, ideally within an hour if you can. If you can't process the woad straight away, keep the leaves in a closed plastic carrier bag and in cool shade but not in the fridge.

3. Steeping the woad leaves
Fill a 10 litre stainless steel saucepan two-thirds full with water. It is best to use soft water, e.g. rain water, if you can. Heat the water up to 90 C but do not let it boil in the saucepan. Turn the heat off, put the leaves in the saucepan (fig. 4) and put the lid on. Let the leaves steep for 10 minutes [some dyers steep the leaves for 20 to 30 minutes or even an hour, so you might like to experiment with different times if you have plenty of leaves]. When the leaves are in the water, the temperature goes down to 80 C, which is the temperature that you want.

4. Cooling the woad liquid
Remove the saucepan from the heat as soon as the 10 minutes are over and put it in a sink half full of cold or icy water (fig. 5). According to Dr Hill, the liquid must cool down quickly to prevent the woad pigment from breaking down.

You should aim to get the liquid down to 55 C in 5 minutes. Keep stirring the saucepan and changing the water from the sink. You can even put a tray of ice cubes in the sink to cool the woad liquor more quickly.

5. Straining the woad liquor
When the liquid has reached 55 C, put a colander over a bucket and then strain the liquid through the colander (fig. 6), saving the liquid.

Put on rubber gloves to press the leaves and to extract all the liquid (fig. 7). Pour the liquid back into the saucepan leaving any debris behind in the bucket. The spent leaves can then go on the compost.

6. Adding soda ash to woad liquor
Fill a Pyrex jug with 250 ml of boiling water and add 3 teaspoons of soda ash, dissolve well and let it cool slightly (fig. 8).

After the liquid in the saucepan has cooled to 50 C, add the soda ash. Do not put soda ash when woad solution is over 50 C or you will destroy the blue.

The liquid will turn to a greenish-brown colour. Measure the pH (fig. 9) which should be alkaline and about 9. If the pH is below 9 and more acid (for example, 7 or 8), add a little more soda ash.

B. Extracting the woad pigment (opens a new page)
 7. Aerating the woad liquid
 8. Settling out the woad pigment
 9. Cleaning the woad pigment
10. Drying the woad pigment
11. Filtering the woad pigment
12. Dyeing with woad

Looking for the previous page on woad pigment extraction? The old text & photos for extracting woad pigment are here.

Top of page
 

Teresinha at Woad.org.uk
Studio 319, Scott House, The Custard Factory
Gibb St, Birmingham B9 4DT, UK

Contact Teresinha for enquiries on
Tel:      +44 (0)7979 770 865
email:    info@woad.org.uk

[Home] [Contact us] [Orders] [FAQ] [About us] [Links] [Sitemap]

UK Postage 4.95p on orders to 70 in value, free over 70 in UK
(post to Europe/rest of World - click here)

Last updated on 28 June 2017
Website & photos - Mike Roberts © 2006-17 woad.org.uk