In a 6- to 8-quart heavy pot combine juice and pectin. Bring to a full rolling boil, stirring constantly. Stir in sugar. Return to a full rolling boil, stirring constantly. Boil hard 1 minute, stirring constantly. Remove pot from heat. Quickly skim off foam with a metal spoon.
Ladle hot jelly into hot, sterilized half-pint canning jars, leaving a 1/4-inch headspace. Wipe jar rims; adjust lids and screw bands.
Process filled jars in a boiling-water canner 5 minutes (start timing when water returns to boiling.) Remove jars form canner; cool on wire racks.