Natural Dyeing with Tansy and Iron Mordant

Summer is waning, and it’s time to harvest the gifts of the garden. This year I was blessed with a bounty of Tansy (Tanacetum vulgare) which I grew for natural dyeing. This is my first time dyeing with tansy, and I’m pleased with the result, although I still have a lot to learn about natural dyeing!

Preparing the Dye Bath

I started by cutting the fresh tops, including flowers and leaves, while the plant was in bloom. I filled a stockpot to the top with the plant matter, and discarded any woody stems.

I covered the tansy with water, and put the pot on the stove on high heat. Once the water started boiling, I lowered the heat, covered the pot with a lid, and let it simmer for two hours.

Mordanting the Yarn

While my dye bath was boiling, I mordanted the yarn. For this project, I chose a 50/50 cotton and wool blend grown and milled in Virginia. You want approximately the same amount of fiber as dyestuffs. I had about one pound of each. The yarn started as a natural white color.

To make the mordant, I brought 2 quarts of water to boil in a stock pot (used only for dyeing). I added two tablespoons of alum (aluminum acetate) and one tablespoon of cream of tartar. Once the powder was fully dissolved, I removed the mordant from heat and added the yarn to soak.

(For more detailed information on mordanting, see the Botanical Colors website.)

Cooling the Dye Bath and Mordanting Yarn Overnight

After the dye pot had simmered for two hours, I removed it from heat. I let the dye bath and the yarn in the mordant solution cool overnight.

Adding the Yarn to the Dye Bath

The next morning, I strained the dye bath to remove the plant matter. I then removed the yarn from the mordant bath, squeezed out any excess liquid, and added it to the dye bath. There needs to be enough liquid for the yarn to freely move around in the dye bath. Mordant can be saved and used again.

Once all the yarn was added, I heated the dye bath on medium to just below boiling. (The dye pot should be hot and steaming, but not boiling.) I then lowered the heat and let the dye pot simmer for an hour.

The yarn became a lovely soft yellow. If you want yellow, you can let the dye pot simmer for a total of two hours. I decided I wanted to try for olive green. Once I saw the yellow color was saturated, after about an hour of simmering, I added 1/2 cup of iron mordant. (Iron mordant is rusty iron scraps in white vinegar allowed to sit for a month. I make it using bits of old iron found on the farm and keep it on hand.)

The dye bath immediately and magically turned an olive green! I mixed the yarn in the bath to ensure even color saturation and let it simmer for another hour. I then removed it from heat and let it cool several hours. Once cool, I washed and rinsed the yarn and hung it on the line to dry.

The yarn is a lovely sage green, and listed in the shop! If you would like to dye your own tansy yarn, below is a list of items you will need:

  1. Plant matter, fresh or dried
  2. Yarn of plant or animal fiber, or a blend
  3. Appropriate mordant
  4. Iron mordant, if desired
  5. Particulate mask and latex gloves, available at your local hardware store
  6. Stock pots, strainer, tongs and other utensils reserved for dyeing
  7. Water, filtered or spring if you have hard water

I also used some of the flower heads to Hapazome print a remnant of fabric that was already eco printed with fresh leaf indigo from my garden. I’m hoping to make a project bag or two.

Watch the video here!

Published by Alissa Head

Neurodivergent Creative living on a few acres of mostly woodland in rural Ohio. Owner of Chestnut Hills Farm and Fiber. I blog about knitting, sewing, spinning, dyeing, gardening, and the occasional gluten free recipe. Also: Horror fan. Paranormal enthusiast. Tudor nerd.

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