4 c. juice of plums (4 lbs. of ripe plums)
1 pouch Certo fruit pectin
6 1/2 c. sugar

To get juice of plums, pit (do not peel) and finely chop plums. Place in saucepan. Add 1 cup water. Bring to a boil. Cover and simmer 10 minutes. Use strainer for clearer jelly. Have jars prepared, by washing jars with hot water, and place lids in boiling water for 10 minutes. Stir sugar into juice. Mix well. Add 1/2 teaspoon butter. Bring mixture to full rolling boil over high heat, stirring constantly. Add Certo fruit pectin and quickly stir. Bring to full boil, and boil 1 minute, stirring constantly. Remove from heat. Skim off any foam. Fill jars immediately. Wipe jar rims and threads. Spoon out any bubbles in jars. Cover quickly with lids. Invert jars for 5 minutes, then turn upright. Check seals after 1 hour.