1. Rinse blueberries and remove stems or debris. Crush slightly with a potato masher.
2. Combine crushed blueberries and water in a large saucepan. Bring to a boil, then reduce heat and simmer for about 10 minutes.
3. Remove from heat and strain through a jelly bag or fine mesh strainer. Let drip naturally for several hours or overnight for clear juice.
4. Measure 4 cups of blueberry juice into a large pot. Stir in pectin and bring to a full rolling boil over high heat.
5. Add all sugar at once, stirring to dissolve. Return to a full rolling boil and boil hard for 1 minute, stirring constantly.
6. Remove from heat, skim off foam, and stir in lemon juice.
7. Ladle hot jelly into prepared jars, leaving 1/4 inch headspace.
8. Process in a boiling water bath for 10 minutes (adjust for altitude).
9. Remove jars and let cool undisturbed for 12–24 hours. Check seals before storing.

Storage

1. Store sealed jars in a cool, dark place for up to 1 year
2. Refrigerate after opening