American mountain-ash (Sorbus americana) leaves provide an excellent natural dye in coppery-gold colours. This plant does not often arise in discussions of natural dyes, perhaps because it lacks wide distribution outside the northeastern Laurentian forests of North America. However, European mountain-ash (S. aucuparia), also known as rowan, commonly appears as an ornamental tree and presumably produces a similar pigment. Maybe these colours aren’t the trendiest, but they deserve some attention, given their intensity and the species’ reasonable abundance.
Another drawback is that a copper sulphate mordant is required to yield good colour, so I’ll address the environmental concern.
Mountain-ash has distinctive compound leaves with about 15 serrated leaflets. Clusters of white flowers in late spring give way to red, berry-like fruit ripening in the fall. They are edible but not especially tasty. They are small trees. Here’s the sapling that stands sentry beside our dock.
S. americana is found in Northern Ontario, Quebec, the Atlantic provinces, New England, the Appalachians, Northern Michigan, Wisconsin and Minnesota. Note that it is endangered in Illionois, so avoid harming a tree. Leaves can be harvested in late September without consequence, and the dye colour might be even better at that time.
When I first took an interest in natural dyes, I found reference to mountain-ash in Spectrum: Dye Plants of Ontario by Nancy J. McGuffin. At the time, one large tree grew behind our cottage. So one day in September 2008 I climbed onto the roof (a challenge to my acrophobia), plucked leaves and passed them down to my partner. With the benefit of Danny’s dyeing experience, we achieved the impressive copper colour, with complex gold undertones, shown below (the top skein of yarn was dyed with black locust pods, not quite as interesting).
I have always wanted to experiment further. So last weekend with some free time at the cottage, we tried it again, with even more interesting, if less predictable, results.
I climbed onto the roof again. It was a lot more nerve-wracking this time. The cottage has a new metal roof, offering hardly any purchase for my footing, except the occasional rivet. I retrieved all the leaves I could from a seated position. Fortunately, a number of saplings have appeared along our lake shore, as in the photograph above. We thinned them, leaving the strongest to maintain a future population. Altogether we collected 1.8 kg (4 lbs.) of leaves.
This dye requires a relatively high plant-to-fibre ratio of 4:1. So we used 600 g (1.3 lbs.) in each of two pots to dye 150 g (5.3 oz.) of fibre. The remaining third we brought home and are drying for another time.
My fibre interest has shifted away from commercial yarn to fibre, for blending and hand-spinning my own yarn. I brought rovings of Rambouillet wool, 70%/30% alpaca-wool blend, and Bombyx and tussah silk to the pot. Also, with every dyeing exercise I have included some Border Leicester locks. This is a coarse but glossy wool I plan to spin into tapestry yarn, so I’m building a palette of colours. Danny’s project was a skein of lace-weight silk yarn (results below).
Mountain-ash leaves need to be soaked overnight, then brought to a boil and simmered for two hours. They don’t seem to release as much pigment, but don’t be deceived: the outcome will be intense.
After two hours, the leaves can be strained out and the fibre added to the dye water and simmered. That was how we did it in 2008. This time we had the leaves bundled in mesh bags, so we left them with the fibre for the first hour of dyeing. After the first hour, the leaves and fibre come out and the mordant is added to the pot, copper sulphate at two percent (3 g per 150 g of fibre). After it dissolves, the fibre returns to the pot for another hour. Waiting to add mordant halfway through ensures the dye has time to penetrate the fibre and doesn’t all bind with the mordant in the water.
Afterward we turned off the heat, and let the fibre sit and cool in the pots overnight to soak up as much pigment as possible. Then the fibre must be removed and given an after-bath in a basic, not acidic, solution. McGuffin used ammonia and we followed her advice in 2008. This time we tried baking soda. I also tried some samples in clear water and an acid after-bath with some vinegar. The difference was barely noticeable, although the base sample was slightly redder and darker. Here’s how the Border Leicester locks turned out.
We had much more inconsistent results this time. The dye seems to have two components: an orange-copper-brown and a brassy gold. The silks picked these up in a variety of ways. Danny’s yarn turned out with an attractive variegation. The dye didn’t penetrate my silk rovings or locks consistently, so they have lots of shades including scarlet, dark copper, peach, brass and pale gold. Below are the Rambouillet, Bombyx silk and alpaca-wool rovings.
The Rambouillet and Border Leicester picked up the orange-copper most consistently, taking on the deepest tones. The alpaca-wool blend seemed to resist this colour, taking on more of the gold, so the result was a light peachy brown.
This might have been a frustrating experiment if we had expected the same solid colour as 2008, but for my purposes the variety is more interesting than disappointing. For more consistent results we might try pre-soaking the fibre longer (our silk was soaked overnight, as it normally needs to be, but we didn’t add any soap to the water). For the future I might try harvesting leaves in September again, to see if the pigment intensifies later in the season, as is the case with some plant dyes. Including silk in the pots, which tends to absorb a lot of pigment quickly, may have affected the uptake by other fibres. Here are the Rambouillet, alpaca-wool and Border Leicester after they dried.
Natural dyes, used in the traditional way, are not very environmentally friendly. Most require metal salt mordants, many of which are fairly toxic. Mordants bind pigments to the fibre. Alum is a safe option. Unfortunately it does not provide good colours with mountain-ash.
Synthetic dyes can provide great colour and more versatility with less environmental impact. Meanwhile, many fans of natural dyes are trying to develop safer procedures. For this reason, many will not use mordants such as copper sulphate.
Although copper occurs naturally in soils and is an important fertilizer for plants, concentrated copper sulphate is toxic to many organisms, notably bacteria and fungi. If leached into rivers and streams, it can lead to fish die-off.
The absolute amount and concentration of copper used in occasional dyeing are small, and probably safe if used and disposed of carefully. It is safe to dispose of these die baths down the sink with lots of water, if and only if it drains into a sewer. Do not dispose of copper sulphate into a septic tank, where it will kill essential microorganisms.
Our cottage has a septic bed, so instead I dumped the dye pots along the gravel road where the water can diffuse and dilute before entering the surroundings. It would be unsafe to do this frequently or with large amounts of dye. Most natural dyes work well with safer mordants, so I will reserve copper sulphate for occasional use with this particular favourite.
Another environmental concern with natural dyes is the amount of water required for the process and safe disposal. We have a huge supply of clean lake water at the cottage, but I would never take this for granted.
It’s hard to beat spending a long weekend in my happy place, playing with a plant I have grown to admire for it’s natural dye.