4 c. crushed blackberries (fresh)
7 c. sugar
1 pouch Certo fruit pectin
1/2 tsp. butter

Stir sugar into berries; add butter. Bring mixture to full rolling boil, stirring constantly. Quickly stir fruit pectin into fruit mixture and boil 1 minute, stirring constantly. Remove from heat; skim off any foam. Fill jelly jars to 1/8 inch of top. Invert jars 5 minutes, then turn upright. Cool. Store and refrigerate after opening.