Standard Protective War Water
- Place iron nails in a mason jar. Cut iron nails are recommended because they rust very easily, but any iron nails may be used.
- Add enough water to cover the nails. Leave this undisturbed until rust begins to form, typically within seven to ten days. Although the jar is usually kept shut, it should be opened periodically to encourage oxidation.
- Once the rusting process begins, more water may be added. Keep the jar in a refrigerator or other cool area.
- Strain the water and use as needed.
You may continue adding water to the original nails virtually
indefinitely. Some people have a War Water starter lasting
years, akin to a sour dough starter. However, should mold or
bacteria ever form, discard everything, including the jar and
start again from the beginning.
(from The Element Encyclopedia of 5,000 Spells by Judika Illes)