How to Dye Wool Yarn with Black Walnuts Using a Mordant and Simmered Dye Bath

Materials & tools you'll need

Step 1 — Scour the wool skein

Wash the wool skein in a pot of hot water mixed with pH-neutral dish soap, soaking for about 30 minutes. This removes any remaining lanolin from the wool, which would otherwise stop the fiber from absorbing dye evenly in the mordanting and dyeing stages ahead.

Step 2 — Prepare and apply the mordant (optional)

Rinse the scoured yarn under cool water to remove any soap residue. If you're mordanting, combine alum powder or aluminum sulfate with cream of tartar powder in enough water to fully submerge the yarn. Submerge the clean, rinsed yarn in the mordant solution for about an hour at a low-medium heat, roughly 80–90°F, to help the dye bond more permanently to the fiber. This step is optional — black walnut dye will still take on unmordanted wool — but it does improve colorfastness.

Step 3 — Simmer the black walnuts to make the dye bath

Chop your black walnuts and cover them with water in a separate pot. Simmer for approximately an hour to an hour and a half, extracting as much color as possible from the walnuts. The longer they simmer, the darker and more concentrated your dye bath will become.

Step 4 — Dye the yarn

Once the walnut dye has sufficiently darkened, carefully remove the yarn from the mordant solution, if you used one, and submerge it in the walnut dye bath. Stir the pot occasionally to encourage even coverage across the skein. The longer you leave the yarn in the dye, the darker the final color will be — check periodically and pull it once you're happy with the shade, keeping in mind the color will continue to deepen slightly as it oxidizes.

Step 5 — Rinse and dry

When you're happy with the color, rinse the dyed yarn under cool water until it runs clear, removing any excess dye. Hang the yarn up to dry fully before moving on to finishing — you'll notice the brown continuing to deepen slightly through this oxidation process, even after the yarn is out of the dye bath.

Step 6 — Weave in ends and block

Once fully dry, weave in any loose ends or trim them as needed. For the best finish, block the yarn by soaking it briefly in warm water with a small amount of pH-neutral dish soap, then gently stretching it out on a flat surface to dry. Blocking helps the yarn hold its shape and gives better stitch definition in whatever project you use it for.

Frequently asked questions

Do you have to mordant wool before dyeing with black walnuts?
No — black walnuts contain natural tannins and will dye wool without a mordant. Mordanting with alum and cream of tartar is optional here, but it helps the dye bond more permanently to the fiber and can improve colorfastness over repeated washes.

How long should you simmer black walnuts to make a dye bath?
Chop the walnuts, cover them with water, and simmer for about an hour to an hour and a half. This gives enough time to extract a dark, concentrated dye bath before you add the yarn.

Can you use any natural wool for this dye, or does it need to be a specific brand?
Any natural, undyed wool skein will take black walnut dye well. Briggs and Little Regal Wool in Wash White is a good, readily available option, but the process works the same with other natural white or cream wool yarns.

Why does black walnut dyed yarn keep changing color after dyeing?
Black walnut dye continues to oxidize on the fiber for a short time after dyeing, deepening from a lighter tan toward a richer, darker brown as it dries and cures. This is a normal part of the process, not a sign anything went wrong.

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