- 10 tablespoons medium-ground full-flavored coffee
- 10 cups cold water (preferably filtered)
- 5 empty eggshells, crushed
- Bring all ingredients to a full boil in a large nonreactive saucepan, partially covered, then simmer, tightly covered, 5 to 7 minutes.
- Let stand, covered, off heat until grounds settle, about 2 minutes. Carefully strain through a fine-mesh sieve into a pot.