Return jelly to a vigorous boil, stirring constantly, and boil, stirring constantly, 1 to 2 minutes (mixture will thicken slightly).
Remove from heat.
Carefully remove sterile jars and lids with canning tongs, then drain jars upside down on a clean kitchen towel and quickly dry lids.
Invert jars and immediately ladle hot jelly into jars, leaving 1/4 inch of space at top. (Last jar may not be full.)
Run a clean plastic spatula between jelly and sides of jars to eliminate air bubbles.
Wipe off rims of filled jars with a damp clean kitchen towel, then firmly screw on lids with screw bands.
Put sealed jars on rack in canner or pot and add enough hot water to cover by 2 inches. (If you have a jar that is partially full, do not process it. Cover it with a lid and screw band, allow to cool completely then keep in refrigerator.)
Bring to a full boil, covered, then boil jelly, covered, 15 minutes.
Transfer jars with canning tongs to a towel-lined surface to cool. Jars will seal; if you hear a ping that means that the vacuum formed above the cooling jelly has made the lid concave. Remember that you may or may not be around to hear the ping. The important thing is for the jars to eventually have concave lids. Jelly will thicken as it cools.
After jars have cooled, 12 to 24 hours, press center of each lid to check that it’s concave, then remove screw band and try to lift lid with your fingertips. If you can’t, the lid has a good seal. Replace screw band. Put any jars that haven’t sealed properly in the refrigerator and use them first (along with jar that was only partially full).
Alternatively ladle the hot jelly into the sterile jars leaving a 1/4 inch space at the top.
Run a clean plastic spatula between jelly and sides of jars to eliminate air bubbles.
Wipe off rims of filled jars with a damp clean kitchen towel, then firmly screw on lids with screw bands.