INTRODUCTION
Although the natural world envelopes us in green there is, surprisingly, no single natural plant dye that can give a bold, bright green. There are plenty of plants that yield up yellow dyes, such as dandelion, golden rod, dyer’s chamomile and others which, with a little iron modifier, will give subtle shades of sage, olive and mossy greens. But to achieve a strident green that would make Robin Hood proud you need to start with blue and overdye with yellow.
For those who don't know, Robin Hood is the legendary outlaw of English folklore who famously stole from the rich to give to the poor. Robin and his ‘Merry Men’ hid out in Sherwood Forest near Nottingham and clothed themselves, it is said, in Lincoln Green.
Lincoln was a major English cloth town in the Middle Ages and Lincoln Green woolen cloth was achieved by first dyeing blue with woad (Isatis tinctoria) and then overdyeing with yellow weld (Reseda luteola) or dyers’ broom (Genista tinctoria).
In the Middle Ages there was a taboo on mixing colours, which was regarded as unnatural. The dyers’ guilds, specialising in one colour, did not readily share their skills with other guilds and severe penalties were enforced for those who dabbled with the devil. However, exceptions must have been granted not just for the dyers of Lincoln, because the green in many medieval tapestries was obtained using a mix of blue and yellow plant dyes.
To provide the blue for this project I’m using indigo, a native of the tropics that was first imported to Europe in the 16th century. Woad (Isatis tinctoria) is a viable alternative with the advantage that it can easily be grown in Europe. For the yellow I’m using weld, another European plant, which gives a strong, bright yellow and can be grown domestically or foraged mid summer.
FIBRES
The high pH level of an indigo vat means that it’s more suited to dyeing robust plant (cellulose) fibres rather than more delicate animal (protein) fibres - though animal fibres can be dyed in an indigo vat once the pH level has naturally reduced after a period of time. For this project I’m using two plant fibres; linen skeins and cotton fabric. These were scoured (well cleaned) but not mordanted as a mordant isn’t necessary when dyeing with indigo.
(see the blog on www.elkatextiles.co.uk : ‘Preparing Plant Fibres for Natural Dyeing’)
WETTING-OUT
I made up three pins, each with linen and cotton samples, and left them to wet out (soak) overnight.
DYEING WITH INDIGO
I had three previously prepared indigo vats; one very pale, one mid and one darker blue.
(For details on preparing an indigo vat see the blog on www.elkatextiles.co.uk : ‘Indigo – King of Dyes’)
A pin of fibres was added to each vat, squeezing out as much water as possible from the fibres to avoid adding more oxygen than necessary. It’s important to keep the fibres beneath the surface of the vat and to move them around from time to time to make sure all surfaces are evenly exposed to the indigo.
Joy Boutrup and Catherine Ellis, in their book The Art and Science of Natural Dyes, recommend at least 10 to 20 minutes per dip to allow the dye to penetrate the fibre.
To achieve an even, solid dye result with indigo it’s necessary to dip fibres more than once. Repeated dipping builds up the colour and 5 or more dips is not unusual, depending on the shade you’re after.
The fibres look a murky yellow/green as they come out of the vat but soon turn blue on exposure to the air. Leave them to air for about an hour between dips to allow the blue to fully develop.
Always bare in mind that the colour of dyed fibres, once they dry, will be several shades lighter than they were as they emerged from the dye pot.
The fibres were then rinsed well and wetted-out again overnight.
MORDANTING
The next step is to mordant the fibres ready for over-dying, first for a couple of hours in a tannin bath .....
.... and then for a couple of hours in an alum / soda ash bath.
As I was going to be away for the next couple of days I then hung them to dry without rinsing.
OVERDYEING WITH WELD
Last summer, as well as the bonus of three weld plants unexpectedly popping up in the garden, I managed to forage some weld – not always easy to find and rarely where you found it the year before! I hung it to dry in the garage for a few weeks before chopping it into pieces - this includes the stem, the leaves and the flowers.
As I was dying approximately 100g of fibre, I weighed out 100g of dry weld (100% WOF). This went into the dye pot and kettle-hot water was poured over the top so the weld could soak overnight to kick-start the extraction of the dye.
At the same time the mordanted fibres were rinsed well to remove excess material and wetted out again.
The next day the weld was heated to 80C, held around that temperature for an hour, and left to cool in the pot. It was then strained through a muslin-lined sieve.
Make sure the dye pot is rinsed clean of ‘bits’ before returning the strained dye, then enter the fibres and heat the dye bath to 80C again, for about an hour.
Pieces of material, such as the square of cotton being dyed here, need to be carefully placed in the dye bath to avoid creases which will dye unevenly. Larger pieces of material would need to be lifted repeatedly in and out of the dye bath to ensure even dye results.
WASHING
.... and then rinsed until the water runs clear.
I decided to have one more go at a darker blue, following the same process, and was happy with this ‘teal’ green. I used a fresh weld dye bath but it's noticeable that at 100% WOF the linen struggled to compete with the darker blue, giving a variegated finish rather than a solid dark green.
TAKE AWAYS
- The cotton squares dyed more evenly than the linen skeins, which was no surprise as linen does not readily take up natural dyes.
- Indigo is a very powerful dye and I think if I was doing this again I’d use a stronger concentration of weld to overdye the darker blues, perhaps 150% WOF. Having said that, the variegated teal blue is attractive in itself. It's just a question of what you're after.
- I only dipped the samples into their respective indigo vats three times, and the results would have been more solid with further dips
- The range of shades attainable, from lime to forest green and everything in between, is just dependent on the respective strengths of the indigo vat and the weld dye bath.
Sadly, you do not get a green dye from spring greens!
References
The Secret Lives of Colour, Kassia St. Clair, 2016
Reddit.com
Theguardian.com
The Art and Science of Natural Dyes, Joy Boutrup and Catharine Ellis 2018
Wikipedia.com
Historic-uk.com