Grape-Plum Jelly

Sterilize jars. Place them right side up on rack in boiling-water canner. Fill canner and jars with hot (not boiling) water to 1 inch above tops of jars. Boil 10 minutes. Remove and drain hot sterilized jars, one at a time, as filled.

Wash and pit plums; do not peel. Thoroughly crush plums and grapes, one layer at a time, in saucepan with water. Bring to boil, cover, and simmer 10 minutes. Strain juice through jelly bag or double layer of cheesecloth. Measure sugar and set aside.

Combine 6 1/2 cups of juice with butter and pectin in large saucepan. Bring to a hard boil over high heat, stirring constantly. Add sugar and return to full rolling boil. Boil hard 1 minute, stirring constantly. Remove from heat, quickly skim off foam, and fill hot, sterile jars, leaving 1/4-inch head space. Adjust lids and process in boiling-water canner for 10 minutes.