Blueberry Raspberry Jam

Crush berries; measure 4 cups (if necessary, add water to make full amount). Add sugar, mix well. Heat to full rolling boil; boil hard 1 minute, stirring constantly. Remove from heat; stir in pectin; skim. Ladle into clean, hot half-pint jars, seal and process in a boiling waterbath for 5 minutes. Notes: This is an old recipe. Current instructions for using Certo have you boiling the mixture for one minute after the addition of the liquid pectin. I think I would.