To prepare a black walnut tincture, you need black walnuts that are still in green hulls, a lidded stainless steel or glass pot, enough vodka to cover the walnuts in the pot, 2 teaspoons of vitamin C powder and some small, dark glass bottles to hold the finished tincture. Multiple small bottles are better than a single large bottle because the tincture loses potency when it is exposed to the air.
Gather green walnuts
When black walnuts grow on trees, they are surrounded by a green outer hull. Gather only walnuts with hulls that are at least half green. Greener hulls produce stronger tinctures.
Prepare the walnuts
Prepare the walnuts by rinsing them under running water. You may need to use a brush to remove dirt from the hulls. Give them a final rinse in unchlorinated water. You can dechlorinate your water by letting it stand overnight in an uncovered container.
Cover the walnuts with vodka
Add the walnuts to a pot, and add enough vodka to cover the walnuts. The air space above the walnuts, after the alcohol is added, should be as small as possible. Sprinkle 1 teaspoon of vitamin C powder over the surface and cover the pot tightly. Allow the walnuts to remain in the liquid overnight at room temperature.
Bottle the tincture
Sprinkle the remaining teaspoon of vitamin C powder over the liquid as soon as you remove the lid. Pour the tincture into darkened glass bottles and seal them tightly. The tincture should retain its potency for several years, as long as the bottles are unopened.