Black Walnut - Juglans nigra - is another one of the dye sources native to the United States. The trees grow extensively from the Piedmont to the mountains and on farther north. I've only seen one or two Black Walnuts growing in the coastal region and the impression I got was they were planted and not naturalized. Black Walnut is considered a substantive dye, meaning it doesn't require a mordant to create lasting, lightfast color. However, some experts like Jim Liles recommend using a mordant on your fibers, which will act as a color changer. If you have an iron pot, this is the dye to use in it, as Black Walnut has quite an affinity for iron. If you don't have access to an iron pot then add a little dissolved iron to the dye bath. The hulls contain a large amount of tannin as well as juglone, the source of it's color.
In her book "Want Natural Color?", Jeanie Reagan suggests using either fresh green hulls equal to the weight of the fiber or dried brown hulls at a quarter the weight of the fiber in the dye pot, throwing in some sumac or black walnut leaves (which contain tannin), covering the pot as light will cause oxidation and letting it sit for 2-5 days. The longer you let it sit, the darker it will be, but also the stinkier it will become. After soaking the hulls, add 1 cup of vinegar and boil for 2 hours, let cool and strain. Then add creme of tartar at 5% weight of fiber and if not using an iron pot, add iron at 2% weight of fiber. Stir well and add enough water to make 4 gallons. Add your scoured fiber and bring to a simmer and hold there for one hour. Turn off heat and let sit overnight. Remove fiber, wash and rinse. You should end up with a warm reddish brown.
When using commercial dried and ground Black Walnut, use at 100% with weight of the fiber.
This method is based on the French technique from the Manufacture des Gobelins in Paris, a tapestry weaving center. Sometimes I'm a lazy dyer. I will gather the hulls (I don't even remove the nuts, like I said, this is the lazy method) and put them in a large plastic garbage can and then place that in a tin trash can. I don't want the walnuts to react with the tin trash can, but don't want animals such as racoons or squirrels to chew through the plastic one. I then cover with water, up to the top and occasionally stir with a large stick. The one I had when I lived in the mountains was four years old when I moved and emptied it, it produced beautiful browns. You can drop scoured skeins of yarn or fabric in the black liquid and depending on how long you leave them determines the color. It is possible to get anything from a light tan to a dark brown. This is considered a cold dye method. If you want an almost black, take out some of the liquid, add a little water and heat at 180 F for an hour. With the addition of a little logwood or overdyed with indigo, it is possible to get a good black. Black Walnut and especially iron can make wools and silks a little harsh so be mindful of your practice.
The leaves and green hulls also have medicinal properties. Traditionally, the leaves were decocted and used topically as an antiseptic wash for sores and skin infections. The juice of the hulls was believed to cure ringworm and other skin issues.
Reference books for this post are:
"Want Natural Colour?" by Jeanie Reagan
"The Art and Craft of Natural Dyeing" by Jim Liles
"Medicinal Plants of the Southern Appalachians" by Patricia Kyritsi Howell