Blackberry Jam- Makes 24 8oz jelly jars.
4 quarts blackberries, cut and crushed to yield 5 cups crushed berries.
14 cups sugar
1 3 1/2 oz box pectin
Pour crushed berries into large stockpot. Measure sugar into separate container and set aside. Stir package of Sure-Jell into blackberries. Bring berries and Sure-Jell to a full rolling boil, then stir in sugar quickly. Return mixture to a full rolling boil and boil exactly 1 minute, stirring constantly. Remove from heat and skim foam from top with a metal spoon.
Prepare jars, rings, and lids by heating them in boiling water for at least 5 minutes. When the jam is ready, remove jars and lids and place on dry towel. Fill each jar, leaving 1/2-inch of space at the top of each jar. Wipe jar rims with a clean, damp cloth, place lids onto jars, and screw on rings.
Place filled jars in a hot water bath. Return water to a simmer, adding more water if needed to cover the jars by at least 1/2 inch. Bring water to a boil. Cook at a steady boil to process the jars until fully sealed, about 15 minutes. Turn off heat and let jars rest 5 minutes before removing and cooling on a clean, dry towel placed on kitchen counter or table. Check that the lids have sealed, and store in a cool, dark place for up to 1 year.