5 cups ripe Blenheim apricots (about 3-1/2 lb.)
1/4 cup fresh lemon juice
7 cups sugar, measured into separate bowl
1 box Sure-Jell fruit pectin (powder)
1 teaspoon pure vanilla extract
1/2 teaspoon butter or margarine (helps reduce foam)
Bring boiling-water canner, filled two-thirds with water, to simmer. Wash jars in dishwasher and keep warm. Wash screw bands in hot soapy water; rinse with warm water. Pour boiling water over flat lids in saucepan off the heat. Let stand in hot water until ready to use.
Finely chop unpeeled apricots. Measure exactly 5 cups prepared fruit into heavy-bottom 8-quart sauce pot. Stir in lemon juice.
Stir pectin into prepared fruit in saucepot. Add butter. Bring mixture to full rolling boil (boil that doesn’t stop bubbling when stirred) on high heat, stirring constantly. Stir in sugar. Bring to full rolling boil and boil 1 minute stirring constantly. Add teaspoon vanilla extract. Remove from heat. Skim off any foam with metal spoon.
Ladle jam immediately into prepared jars, filling to within 1/8 inch of tops. Wipe jar rims and threads. Cover with two-piece lids. Screw bands tightly.
Place jars on elevated rack in canner. Lower rack into canner. (Water must cover jars by 1 to 2 inches.) Cover with lid and bring water to gentle boil. Process 10 minutes. Carefully remove jars and place upright on a towel to cool completely. Allow to sit undisturbed for 24 hours. After jars cool, check seals by pressing middles of lids with finger. (If lids spring back, lids are not sealed and refrigeration is necessary.)
Allow about two weeks for jam to set completely. Always store preserves in cool, dry, dark place.