Cowboy Coffee

4 quarts water
1 1/2 cups freshly ground coffee
1 egg shell
1/2 cup cold water

Bring water to a boil in a large saucepan or coffee pot. Add coffee grounds and egg shell to boiling water. Return to a boil, then remove from heat and let stand for 2 minutes. Slowly add cold water to settle grounds to the bottom. Strain if desired.