I have now experimented with a stronger vat, this time using 2 teaspoons indigo, 4 teaspoons calcium hydroxide and 6 teaspoons fructose – that is, double the quantities used in my first vat.

I dyed the same quantities of fibres following the same methods but the depth of blue I achieved was no deeper than from the first, weaker, vat. This would indicate that this vat gives pale to mid blues but not the deep blues which other indigo dyeing methods give. I wonder whether this vat may be best used for patterning fabrics employing resist techniques, rather than for dyeing skeins of fibre as I tend mainly to do. I also noticed that this vat left the wool feeling rather harsh. However, I didn’t use a vinegar after-bath, which might have been advisable to counteract the effects of the strong alkalinity of this vat. (I never usually use a vinegar after-bath, so I’m afraid it didn’t occur to me to do so after this vat.)

If anyone else has any comments to add on using this type of indigo vat, I’d be delighted to receive them.

I have been keen to experiment again with the native bedstraws but, since we moved house and I left my precious dye garden behind, I have been finding it difficult to harvest suitable bedstraw roots. The roots of the Lady’s Bedstraw (Galium verum) plants that I have planted in my new garden are too immature and it is against the law to uproot plants in the wild, so it seemed that any experiments might have to wait a year or two for my own plants to be ready to harvest.

However, thanks to the generosity of Leena Riihela in Finland (www.riihivilla.com) who kindly sent me some roots from her own garden, I have been able to experiment with Hedge Bedstraw, (Galium mollugo).

Compared with the roots of madder (Rubia tinctorum), bedstraw roots are very fine and delicate, and these bedstraw roots were very precious as they had come from such a long way away. So I wanted to make sure that I didn’t waste them.

For these tests I used mainly alum-mordanted wool, except for some unmordanted samples from the exhaust dyebaths. To prepare the dyebaths, I first soaked the roots overnight in water, then poured off this liquid. I then steeped the roots twice in boiling water for about 1 minute each time and added this liquid to the soaking water to make the first dyebath. I then simmered the roots twice more, using each simmering liquid for a separate dyebath. In the photos below, the orange colours on the left were from the soaking water plus the two steeping waters and also from the first 2 simmerings. I then simmered the roots again twice for about 45 minutes and used this liquid for another 2 dyebaths. The middle range of shades on the photos were from these 3rd and 4th simmerings, the redder one with an alkaline modifier (washing soda). The range on the right came from exhaust dye baths, with some unmordanted and some alum-mordanted samples. Once the fibres had been added to the dyebath, I didn’t worry too much about the temperature and allowed the dyebaths to simmer gently to improve colour take-up. (This simmering is not something I would do when dyeing with madder – see below)

I decided to work in this way, rather than combining all the extractions, because my belief is that the richest true reds lie under the yellows and browns and the best way to get reds is to first use up these yellows and browns. I don’t know whether this belief is correct but my experiences suggest it seems a good way to get reds rather than oranges. 

I now use this method when dyeing with madder and it seems to work well. After washing the madder roots well, I simmer them to extract the colour for the first dyebath, remove the roots to use again for a second dyebath and then reduce the temperature before adding the fibres.  Once the fibres have been added, I don’t simmer the madder dyebath and I keep the temperature hot but not too hot – i.e. well below simmering point. The roots can then be simmered again to extract more colour for a second dyebath. Indeed, madder is a most generous dye and the roots can often be simmered several times before the dye is exhausted, giving colour for yet more dyebaths.

I think that, when I next dye with the bedstraws, I will probably keep things simpler and try something closer to the method I use with madder. So, after soaking the roots overnight,  I will simmer them once for about 30 minutes and use this solution for my first dyebath. I will then simmer the roots again (probably for about 45 minutes) for a second dyebath and to make sure no precious dye is wasted, I will simmer the roots at least once more for a further dyebath. But first I must wait for my bedstraw roots to be mature enough to harvest.

A range of shades from Hedge Bedstraw (Galium mollugo)

A close-up image of some of  the Hedge Bedstraw colours.

Thanks to Helen Melvin’s booklet on indigo dyeing, “The Colour of Sea and Sky”, and Helen’s comments on the merits of making an indigo stock solution, I decided to experiment again with this method of making an indigo vat. This was the method I first used with indigo over 30 years ago and Helen’s book reminded me of the advantages of the stock solution method, among them the fact that indigo reduces more efficiently in a concentrated alkaline solution and there is therefore less likelihood of wasted, undissolved indigo. Also, using a stock solution means that the colour can be built up relatively easily.

So why did I stop using the stock solution method? The main reason is that the one-step-bath method I generally use now, and which appears in my books, is more practical for one-day workshops, as the vat is quick to make and this enables me to demonstrate how to make and use an indigo vat in a short space of time. However, after we have used this vat there is often some indigo remaining, which gets thrown away, (unless students can take some solution home with them). Indeed, I often tell students that this vat is even better on the second day, as the indigo has had more time to reduce completely. The other reason for abandoning the stock solution method is my desire to avoid the use of caustic soda, which can cause bad burns if not used with great care.

Helen’s stock solution recipe is quite simple and involves mixing 50gms of indigo powder with 2 tablespoons each of caustic soda (the alkali) and thiourea dioxide (the reducing agent).

For my stock solution I used sodium hydrosulphite (hydros) as the reducing agent and this also works perfectly. I first mixed the indigo powder to a smooth paste in 4 tablespoons of very hot water in a large heatproof jar. I then topped this up with hot water but no hotter than 50C, which is about as hot as a hand can tolerate. (NOTE: Don’t fill the jar too full and leave enough space for any bubbling or fizzing that may occur.) Then I very gently stirred two tablespoons of caustic soda into this solution, followed by two tablespoons of sodium hydrosulphite (or use thiourea dioxide instead of hydros). This is the stock solution. NB Remember to wear rubber gloves and bear in mind that both caustic soda and the reducing agent should be added carefully to water and never pour water directly onto them.

Keep the jar warm and after about 45 minutes the stock solution mixture will become a clear amber colour, although the surface, which is in contact with oxygen from the air, will be a dark blue colour with a lustrous sheen. The stock solution is now ready to use.

To make the vat, fill the container up with water no hotter than 50C, add a teaspoon of hydros (or alternative reducing agent) and a teaspoon of washing soda and allow to stand for a few minutes. Then gently stir in one or more tablespoons of stock solution, according to the size of the vat and the depth of blue required. The vat can then be used as usual and more indigo stock solution can be added as necessary.

Further information on making and using a stock solution and many more recipes can be found in Helen’s booklet “The Colour of Sea and Sky”, which I highly recommend. And of course, like all Helen’s books, it has a lovely hand-painted cover.

The photo below shows a range of blues from indigo