Sure-Jell Plum Jelly

Source: Sure-Jell

5 1/2 cups prepared plum juice*
6 1/2 cups granulated sugar
1 box Sure-Jell Fruit Pectin
1/2 teaspoon butter or margarine (optional)

*(made from about 5 pounds fully ripe plums and 1 1/2 cups water)

Boil jars on rack in large pot filled with water 10 minutes. Place flat lids in saucepan with water. Bring to boil. Remove from heat. Let jars and lids stand in hot water until ready to fill. Drain well before filling. Pit plums; do not peel. Finely chop or grind fruit. Place in saucepan; add 1 1/2 cups water. Bring to boil. Reduce heat; cover and simmer 10 minutes, stirring occasionally. Place 3 layers of damp cheesecloth or jelly bag in large bowl. Pour prepared fruit into cheesecloth. Tie cheesecloth closed, hang and let drip into bowl until dripping stops. Press gently to keep juice clear.

Measure 5 1/2 cups into 6- or 8-quart saucepot. Measure sugar into separate bowl (scrape excess sugar from cup with spatula to level for exact measure). Stir fruit pectin into juice in saucepot. Add butter. Bring mixture to full rolling boil on high heat, stirring constantly. Quickly stir in all sugar. Bring to full rolling boil and boil exactly 1 minute, stirring constantly.

Remove from heat, skim off any foam with metal spoon. Ladle quickly into prepared jars, filling to within 1/8 inch of tops. Wipe jar rims and threads. Cover with two-piece lids. Screw bands tightly. Invert jars 5 minutes, then turn upright. After jars are cool, check seals.

Makes about 8 (1 cup) jars.