Ok, so it's not the most vital survival skill (making ink) but it's easy to learn and something most people don't know how to do. Shaggy Mane Inky Caps are edible (at the "all white" stage) and useful. The ink can be used for education, writing messages, deciphering code, documenting history, transferring ownership (a living will or deed to a property), and keeping inventory. The ink costs nothing to make and only two items are needed to utilize it properly, a container to hold the ink and a writing instrument such as a quill or paintbrush. Since it has so many uses and little to no cost, it's a great bartering resource.
Step 1: Forage for Shaggy Mane Inky Cap Mushrooms
They are more common than you might think. Above are three pictures of the Shaggy Mane as it cycles through its life-span. They grow all over the world and can be found in grassy meadows, forests, and even in your backyard (that's where I first discovered them). They grow between the months of April through October.
Step 2: Pick a Half Dozen
Pick 6 to 12 Shaggy Mane mushrooms and place in a container.
Step 3: Wait at Least 12 Hours
After about 12 hours you can start straining the mushrooms for ink. If you don't want to mess with straining, it takes about two weeks for half a dozen mushrooms to completely dissolve into ink.
Step 4: Add Melaleuca Oil
Decaying mushrooms start to smell after several days. Adding a couple of drops of Melaleuca essential oil helps to eliminate the smell. Thyme or Oregano oil works well too.