7 1/2 cups granulated sugar, measured into separate bowl
Bring boiling-water canner, half full with water, to simmer. Wash jars and 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. Drain well
Slip skins from grapes. Finely chop or grind skins; set aside.
Mix grape pulp and water in saucepan. Bring to boil. Reduce heat to low; cover
and simmer 5 minutes.
Press through sieve to remove seeds.
Combine skins and pulp. Measure exactly 6 cups prepared fruit into 6- or 8-quart
Stir in pectin. Add butter to reduce foaming. Bring mixture to full rolling boil
(a boil that doesn't stop bubbling when stirred) on high heat, stirring constantly.
Stir in sugar. Return to full rolling boil and boil exactly 1 minute, stirring constantly.
Remove from heat. Skim off any foam with metal spoon.
Ladle immediately into prepared jars, filling to within 1/4 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. Add boiling water, if necessary.) Cover; bring water to gentle boil.
Process 10 minutes.
Remove jars and place upright on towel to cool completely.
After jars cool, check seals by pressing middles of lids with finger. (If lids
spring back, lids are not sealed and refrigeration is necessary.)