Prepare jars and lids according to manufacturer’s instructions.

In a large saucepan over high heat add blueberries, sugar, butter and lemon juice. Stir frequently while bringing to a rolling boil. Stir in pectin and continue to boil for 1 minute. Remove from heat. Skim any foam if necessary and ladle into the hot prepared jars. Be sure to leave at least 1/4″ space at the top of the jar. Place cap on the jars and process for another 15 minutes in a canner with boiling water.