4 cups blackberry juice (about 3 quarts blackberries)
7½ cups sugar
2 pouches (3 ounces each) liquid pectin
Directions:
Prepare home canning jars and lids according to manufacturer’s instructions; jars should be covered with water and boiled 10 to 15 minutes to sterilize.
Wash fully ripe berries, removing stems or caps.
Crush the berries and extract juice.
Measure 4 cups blackberry juice into a large saucepot; stir in sugar.
Bring to a full, rolling boil over high heat.
Add pectin; return to a full, rolling boil and boil hard 1 minute.
Remove from heat and skim off foam.
Immediately, but carefully, pour into hot, sterilized jars, leaving 1/8-inch head space; adjust caps.
Process in a boiling hot water bath (212F) for 15 minutes.