Yarn Dyeing
I have always been interested in learning how things were made. Since I knit and use yarn a lot, I was curious about how the yarns were dyed and processed, both historically and in the modern day. I attended a hedgerow dyeing course, organised by the Cambridge Art Makers.
We then brought the dyestuff and water mix to a simmer for an hour, while we learnt about the variety and properties of the different dyestuffs we would be working with. These were Heather, Elm Bark, Reeds, Walnut Bark, and Dandelions.
Once the colour had developed in the dye baths, we removed and discarded the dyestuffs (apart from the bark. Because of the natural tannins within bark, they could be dried out and used again in an exhaust bath).
We dissolved the mordant we were using into the dye bath and warmed the fibres in a separate bowl of hot water before then adding them to the bath. We then heated the dye bath for one hour before leaving it to cool. Our instructor told us that, were we doing this at home, we could leave the pan to cool overnight and rinse the fibres out in cold water the next day, but since we were doing it in the workshop, we rinsed them later in the day and hung them up to dry.
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Hedgerow dyes work best on natural fibres, such as wool, mohair, and silk (animal fibres) and linen, hemp, and cotton (vegetable fibres). Natural colours also develop better on animal fibres, while vegetable fibres may require double or triple dyes to achieve the same depth of colour.
One aspect that will affect how much of the dye is taken up by the fibre is what mordant you use.
Mordants
Most dye plants require a mordant to fix them to the fibres. Tree dyes (and some plants like rhubarb) do not need a mordant to fix the as they contain enough of their own tannins (substantive dyes) but using mordants allows you to modify the colour produces and create a range of shades.
Alum: aluminium potassium sulphate. It is safe to handle but I always wore gloves. This mordant works well on animal fibres but too much can make wool sticky to the touch. I used a 1:10 ratio of mordant to dry fibre.
Copper: copper sulphate. This mordant is poisonous and I used gloves and a mask when handling it. It is a brightener and will often deepen the colour compared to alum. I used 4:100 ratio of copper to dry fibre.
Iron: ferrous sulphate. This darkens and saddens colours. When combined with yellow dye stuffs, it can make a good selection of greens. However, iron can weaken and degrade animal fibres over time. I used a 5:100 ratio of iron to dry fibre.
Method
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Preparing dyestuffs
For best results, I was advised to use double the weight of dyestuff to fibre. It is difficult to be exact using hedgerow dyeing since colour results will vary according to the preparation of the fibres, type of fibre, local water and the temperature of the dye bath. Nonetheless, I enjoyed the experimental nature of this method; it was fascinating to learn how generations of people had been dyeing fabric and yarn before us.
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This was an experimental workshop so we were using a wide variety of dyestuffs. The instructor had already set up a series of containers (stainless steel pans or drums) with the dyestuffs inside. The plants had been scalded with boiling water and then topped up with warm water until and left overnight to soak (although the bark had been left for 2-3 days in advance of the class).
My own experiments
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I was allowed to take the Elm Bark dye bath home and did some of my own experiments.
I wanted to test what the effect of time and exposure had on yarn, i.e. how dark could the colour get?
I divided a hank of undyed, un-mordanted yarn into three sections and soaked them in the re-heated dye bath. After an hour, I turned the heat off and allowed it to cool. After three hours, I removed the first hank of yarn, which had taken up the tannins within the dye and was a light pink.
After a further three hours, I removed the second hank of yarn and, as I had predicted, it had become a darker, stronger brown.
I left the remaining hank of yarn in the dye bath overnight and assumed that it would be the same or a darker shade to the second yarn hank. However, after checking in the morning, I was surprised to find that it was actually lighter. After speaking with the instructor of my class about it, we decided that it could be because most of the dyestuff was taken up in the first 6 hours (the dye bath I was using being what was left from the course), and beyond that point, there was not enough dyestuff to fibres to produce a stronger colour.
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I also wanted to test what would happen if I mixed dye stuffs. I created two new dye baths, one with Heather and one with Elm Bark. I used an alum mordant and immersed a hank of yarn in the Heather bath for 3 hours. Once out, I divided it into 4 sections, one of which was laid aside and rinsed, while the other three were immersed in the Elm bath.
I removed the first hank after three hours. Although no other mordants were added, the tannins in the Elm Bark had clearly managed to darken the pre-dyed yarn into a light fawn brown.
I removed the second hank after a further 17 hours had passed. It was a similar colour to the first and I therefore concluded that the fibres had already absorbed the maximum amount of dye.
The third has was removed after a total of 44 hours in the bath, and was only slightly darker.
