Mixed Berry Jam

• In a 8-quart saucepan, cook the strawberries, blueberries and blackberries over low to medium heat until soft. Lightly mash the fruit with a potato masher. Meanwhile, prepare a boiling water canner. Heat the jars and lids in simmering water until ready to use. Do not boil. Set bands aside.
• In a large measuring cup, combine 2 cups sugar with the pectin. Add the lemon juice and sugar-pectin mixture to the berries. Over high heat, bring the mixture to a full rolling boil that cannot be stirred down, stirring frequently with a wooden spoon. Boil for 1 minute. Add the remaining 5 cups of sugar immediately, and bring back to a hard boil for 1 minute, stirring constantly. Turn the heat on low to medium. Skim foam if necessary.
• Ladle hot jam into the hot jars, leaving ½ inch head-space. Wipe the rim of the jar with a damp paper towel. Center the lid on the jar. Apply the band until the fit is fingertip tight. Process jars in a boiling water canner for 10 minutes, adjusting for altitude. Remove the jars and allow to cool completely. Check the lids for seal after 24 hours. The lid should not flex up and down when the center is pressed. Store jars in a cool, dry place.