Natural plant matter, that may already be in or around your yard, is an economical and environmentally sound option for making dye. Making your own dye, gives you even greater ownership and control over the projects you craft. One of the more difficult dye colors to make is black since there are few black plants or fruits from which you can extract that color. The most effective source of natural black dye is oak galls. These are growths on oak trees that are created by natural plant hormones and chemicals released by inhabiting insects.
The dye created by the galls is a true black, surprising as the galls are green to light brown, according to the Tehachapi (California) News. In reporting the July 2008 visit of Native American basketmakers, demonstrating the dye process, "Oak Stem Galls Used for the Blackest Dye Imaginable" notes that after adding the galls the mixture is clear and dying looks "unlikely," but the brew eventually becomes dark black.
Gather oak galls and smash them with a hammer. Get them into small, manageable pieces.
Chop up the oak gall with a knife. Get each piece down to the size of a raisin or smaller.
Dump the oak gall into a pot. Add twice as much water as there is oak gall. It doesn't have to be a perfect amount, so make your best estimate
Set the pot on the stove and bring it to a boil. Turn the heat down once it boils and let it simmer for an hour.
Put a colander inside a large mixing bowl. Pour the contents of the pot into the colander to separate the oak gall from the liquid. Discard the oak gall. The liquid can now be used as dye.
The dye can be used with a brushing or soaking method. When dying fabric, let it soak in the dye overnight to achieve maximum darkness. Use a rusty iron pot or add a rusty nail or two to your dye as the rust helps the dye become more permanent. Acorns may also be used.