Place 1 cup of berries in an 8-quart heavy pot. Crush berries. Continue adding berries and crushing until you have 5 cups crushed berries. Stir in pectin and butter. Heat on high, stirring constantly, until mixture comes to a full rolling boil. Add sugar all at once. Return to boiling; boil 1 minute, stirring constantly. Remove from heat; skim off foam with a metal spoon.
Ladle at once into hot, sterilized half-pint canning jars, leaving a 1/4-inch headspace. Wipe jar rims; adjust lids. Process in a boiling-water canner for 5 minutes (start timing when water returns to boil). Remove jars; cool on racks.
Jam may need to stand for 1 to 2 weeks after canning to become fully set.
If your fruit separates from the liquid in the jars, invert the sealed jars once or twice a day. Continue inverting until fruit is well distributed.
Prepare as directed except do not crush strawberries. Substitute 8 cups coarsely chopped berries for the 5 cups crushed berries. Makes about 9 cups (about 9 half-pints).
Prepare as directed except decrease crushed strawberries to 4 cups and add 1 cup chopped banana to the strawberries after crushing. Makes about 8 cups (about 8 half-pints).
Prepare as directed except stir in 1/3 cup snipped fresh basil after skimming off the foam. Makes about 10 cups (about 10 half-pints).
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